* Source Code
Follows is a source code listing for all files that have been open sourced. This code can be found in the ~./samples~ directory.
** Samples
*** Learn Ruby Optional - Beginner Ruby Primer - automation.rb
#+begin_src ruby
  # ./samples/00_learn_ruby_optional/00_beginner_ruby_primer/app/automation.rb
  # ==========================================================================
  #  _    _ ________     __  _      _____  _____ _______ ______ _   _ _ _ _ _
  # | |  | |  ____\ \   / / | |    |_   _|/ ____|__   __|  ____| \ | | | | | |
  # | |__| | |__   \ \_/ /  | |      | | | (___    | |  | |__  |  \| | | | | |
  # |  __  |  __|   \   /   | |      | |  \___ \   | |  |  __| | . ` | | | | |
  # | |  | | |____   | |    | |____ _| |_ ____) |  | |  | |____| |\  |_|_|_|_|
  # |_|  |_|______|  |_|    |______|_____|_____/   |_|  |______|_| \_(_|_|_|_)
  #
  #
  #                                   |
  #                                   |
  #                                   |
  #                                   |
  #                                   |
  #                                   |
  #                                   |
  #                                   |
  #                                   |
  #                                   |
  #                                \  |  /
  #                                 \ | /
  #                                   +
  #
  # If you are new to the programming language Ruby, then you may find the
  # following code a bit overwhelming. Come back to this file when you have
  # a better grasp of Ruby and Game Toolkit.
  #
  # What follows is an automations script # that can be run via terminal:
  # ./samples/00_beginner_ruby_primer $ ../../dragonruby . --eval app/automation.rb
  # ==========================================================================
  
  $gtk.reset
  $gtk.scheduled_callbacks.clear
  $gtk.schedule_callback 10 do
    $gtk.console.set_command 'puts "Hello DragonRuby!"'
  end
  
  $gtk.schedule_callback 20 do
    $gtk.console.eval_the_set_command
  end
  
  $gtk.schedule_callback 30 do
    $gtk.console.set_command 'outputs.solids << [910, 200, 100, 100, 255, 0, 0]'
  end
  
  $gtk.schedule_callback 40 do
    $gtk.console.eval_the_set_command
  end
  
  $gtk.schedule_callback 50 do
    $gtk.console.set_command 'outputs.solids << [1010, 200, 100, 100, 0, 0, 255]'
  end
  
  $gtk.schedule_callback 60 do
    $gtk.console.eval_the_set_command
  end
  
  $gtk.schedule_callback 70 do
    $gtk.console.set_command 'outputs.sprites << [1110, 200, 100, 100, "sprites/dragon_fly_0.png"]'
  end
  
  $gtk.schedule_callback 80 do
    $gtk.console.eval_the_set_command
  end
  
  $gtk.schedule_callback 90 do
    $gtk.console.set_command "outputs.labels << [1210, 200, state.tick_count, 0, 255, 0]"
  end
  
  $gtk.schedule_callback 100 do
    $gtk.console.eval_the_set_command
  end
  
  $gtk.schedule_callback 110 do
    $gtk.console.set_command "state.sprite_frame = state.tick_count.idiv(4).mod(6)"
  end
  
  $gtk.schedule_callback 120 do
    $gtk.console.eval_the_set_command
  end
  
  $gtk.schedule_callback 130 do
    $gtk.console.set_command "outputs.labels << [1210, 170, state.sprite_frame, 0, 255, 0]"
  end
  
  $gtk.schedule_callback 140 do
    $gtk.console.eval_the_set_command
  end
  
  $gtk.schedule_callback 150 do
    $gtk.console.set_command "state.sprite_path =  \"sprites/dragon_fly_\#{state.sprite_frame}.png\""
  end
  
  $gtk.schedule_callback 160 do
    $gtk.console.eval_the_set_command
  end
  
  $gtk.schedule_callback 170 do
    $gtk.console.set_command "outputs.labels    << [910, 330, \"path: \#{state.sprite_path}\", 0, 255, 0]"
  end
  
  $gtk.schedule_callback 180 do
    $gtk.console.eval_the_set_command
  end
  
  $gtk.schedule_callback 190 do
    $gtk.console.set_command "outputs.sprites   << [910, 330, 370, 370, state.sprite_path]"
  end
  
  $gtk.schedule_callback 200 do
    $gtk.console.eval_the_set_command
  end
  
  $gtk.schedule_callback 300 do
    $gtk.console.set_command ":wq"
  end
  
  $gtk.schedule_callback 400 do
    $gtk.console.eval_the_set_command
  end

#+end_src

*** Learn Ruby Optional - Beginner Ruby Primer - main.rb
#+begin_src ruby
  # ./samples/00_learn_ruby_optional/00_beginner_ruby_primer/app/main.rb
  # ==========================================================================
  #  _    _ ________     __  _      _____  _____ _______ ______ _   _ _ _ _ _
  # | |  | |  ____\ \   / / | |    |_   _|/ ____|__   __|  ____| \ | | | | | |
  # | |__| | |__   \ \_/ /  | |      | | | (___    | |  | |__  |  \| | | | | |
  # |  __  |  __|   \   /   | |      | |  \___ \   | |  |  __| | . ` | | | | |
  # | |  | | |____   | |    | |____ _| |_ ____) |  | |  | |____| |\  |_|_|_|_|
  # |_|  |_|______|  |_|    |______|_____|_____/   |_|  |______|_| \_(_|_|_|_)
  #
  #
  #                                   |
  #                                   |
  #                                   |
  #                                   |
  #                                   |
  #                                   |
  #                                   |
  #                                   |
  #                                   |
  #                                   |
  #                                \  |  /
  #                                 \ | /
  #                                   +
  #
  # If you are new to the programming language Ruby, then you may find the
  # following code a bit overwhelming. This sample is only designed to be
  # run interactively (as opposed to being manipulated via source code).
  #
  # Start up this sample and follow along by visiting:
  # https://s3.amazonaws.com/s3.dragonruby.org/dragonruby-gtk-primer.mp4
  #
  # It is STRONGLY recommended that you work through all the samples before
  # looking at the code in this file.
  # ==========================================================================
  
  class TutorialOutputs
    attr_accessor :solids, :sprites, :labels, :lines, :borders
  
    def initialize
      @solids  = []
      @sprites = []
      @labels  = []
      @lines   = []
      @borders = []
    end
  
    def tick
      @solids  ||= []
      @sprites ||= []
      @labels  ||= []
      @lines   ||= []
      @borders ||= []
      @solids.each  { |p| $gtk.args.outputs.reserved << p.solid  }
      @sprites.each { |p| $gtk.args.outputs.reserved << p.sprite }
      @labels.each  { |p| $gtk.args.outputs.reserved << p.label  }
      @lines.each   { |p| $gtk.args.outputs.reserved << p.line   }
      @borders.each { |p| $gtk.args.outputs.reserved << p.border }
    end
  
    def clear
      @solids.clear
      @sprites.clear
      @labels.clear
      @borders.clear
    end
  end
  
  def defaults
    state.reset_button ||=
      state.new_entity(
        :button,
        label:  [1190, 68, "RESTART", -2, 0, 0, 0, 0].label,
        background: [1160, 38, 120, 50, 255, 255, 255].solid
      )
    $gtk.log_level = :off
  end
  
  def tick_reset_button
    return unless state.hello_dragonruby_confirmed
    $gtk.args.outputs.reserved << state.reset_button.background
    $gtk.args.outputs.reserved << state.reset_button.label
    if inputs.mouse.click && inputs.mouse.click.point.inside_rect?(state.reset_button.background)
      restart_tutorial
    end
  end
  
  def seperator
    @seperator = "=" * 80
  end
  
  def tick_intro
    queue_message "Welcome to the DragonRuby GTK primer! Try typing the
  code below and press ENTER:
  
      puts \"Hello DragonRuby!\"
  "
  end
  
  def tick_hello_dragonruby
    return unless console_has? "Hello DragonRuby!", "puts "
  
    $gtk.args.state.hello_dragonruby_confirmed = true
  
    queue_message "Well HELLO to you too!
  
  If you ever want to RESTART the tutorial, just click the \"RESTART\"
  button in the bottom right-hand corner.
  
  Let's continue shall we? Type the code below and press ENTER:
  
      outputs.solids << [910, 200, 100, 100, 255, 0, 0]
  "
  
  end
  
  def tick_explain_solid
    return unless $tutorial_outputs.solids.any? {|s| s == [910, 200, 100, 100, 255, 0, 0]}
  
    queue_message "Sweet!
  
  The code: outputs.solids << [910, 200, 100, 100, 255, 0, 0]
  Does the following:
  1. GET the place where SOLIDS go: outputs.solids
  2. Request that a new SOLID be ADDED: <<
  3. The DEFINITION of a SOLID is the ARRAY:
     [910, 200, 100, 100, 255, 0, 0]
  
        GET       ADD     X      Y    WIDTH  HEIGHT RED  GREEN  BLUE
         |         |      |      |      |      |     |     |     |
         |         |      |      |      |      |     |     |     |
  outputs.solids  <<    [910,   200,   100,   100,  255,   0,    0]
                        |_________________________________________|
                                             |
                                             |
                                           ARRAY
  
  Now let's create a blue SOLID. Type:
  
      outputs.solids << [1010, 200, 100, 100, 0, 0, 255]
  "
  
    state.explain_solid_confirmed = true
  end
  
  def tick_explain_solid_blue
    return unless state.explain_solid_confirmed
    return unless $tutorial_outputs.solids.any? {|s| s == [1010, 200, 100, 100, 0, 0, 255]}
    state.explain_solid_blue_confirmed = true
  
    queue_message "And there is our blue SOLID!
  
  The ARRAY is the MOST important thing in DragonRuby GTK.
  
  Let's create a SPRITE using an ARRAY:
  
    outputs.sprites << [1110, 200, 100, 100, 'sprites/dragon_fly_0.png']
  "
  end
  
  def tick_explain_tick_count
    return unless $tutorial_outputs.sprites.any? {|s| s == [1110, 200, 100, 100, 'sprites/dragon_fly_0.png']}
    return if $tutorial_outputs.labels.any? {|l| l == [1210, 200, state.tick_count, 255, 255, 255]}
    state.explain_tick_count_confirmed = true
  
    queue_message "Look at the cute little dragon!
  
  We can create a LABEL with ARRAYS too. Let's create a LABEL showing
  THE PASSAGE OF TIME, which is called TICK_COUNT.
  
    outputs.labels << [1210, 200, state.tick_count, 0, 255, 0]
  "
  end
  
  def tick_explain_mod
    return unless $tutorial_outputs.labels.any? {|l| l == [1210, 200, state.tick_count, 0, 255, 0]}
    state.explain_mod_confirmed = true
    queue_message "
  The code: outputs.labels << [1210, 200, state.tick_count, 0, 255, 0]
  Does the following:
  1. GET the place where labels go: outputs.labels
  2. Request that a new label be ADDED: <<
  3. The DEFINITION of a LABEL is the ARRAY:
     [1210, 200, state.tick_count, 0, 255, 0]
  
        GET       ADD     X      Y          TEXT         RED  GREEN  BLUE
         |         |      |      |            |           |     |     |
         |         |      |      |            |           |     |     |
  outputs.labels  <<    [1210,  200,   state.tick_count,  0,   255,   0]
                        |______________________________________________|
                                                |
                                                |
                                              ARRAY
  
  Now let's do some MATH, save the result to STATE, and create a LABEL:
  
      state.sprite_frame = state.tick_count.idiv(4).mod(6)
      outputs.labels << [1210, 170, state.sprite_frame, 0, 255, 0]
  
  Type the lines above (pressing ENTER after each line).
  "
  end
  
  def tick_explain_string_interpolation
    return unless state.explain_mod_confirmed
    return unless state.sprite_frame == state.tick_count.idiv(4).mod(6)
    return unless $tutorial_outputs.labels.any? {|l| l == [1210, 170, state.sprite_frame, 0, 255, 0]}
  
    queue_message "Here is what the mathematical computation you just typed does:
  
  1. Create an item of STATE named SPRITE_FRAME: state.sprite_frame =
  2. Set this SPRITE_FRAME to the PASSAGE OF TIME (tick_count),
     DIVIDED EVENLY (idiv) into 4,
     and then compute the REMAINDER (mod) of 6.
  
     STATE   SPRITE_FRAME    PASSAGE OF      HOW LONG   HOW MANY
       |          |             TIME         TO SHOW    IMAGES
       |          |              |           AN IMAGE   TO FLIP THROUGH
       |          |              |               |      |
  state.sprite_frame =     state.tick_count.idiv(4).mod(6)
                                             |       |
                                             |       +- REMAINDER OF DIVIDE
                                      DIVIDE EVENLY
                                      (NO DECIMALS)
  
  With the information above, we can animate a SPRITE
  using STRING INTERPOLATION: \#{}
  which creates a unique SPRITE_PATH:
  
    state.sprite_path =  \"sprites/dragon_fly_\#{state.sprite_frame}.png\"
    outputs.labels    << [910, 330, \"path: \#{state.sprite_path}\", 0, 255, 0]
    outputs.sprites   << [910, 330, 370, 370, state.sprite_path]
  
  Type the lines above (pressing ENTER after each line).
  "
  end
  
  def tick_reprint_on_error
    return unless console.last_command_errored
    puts $gtk.state.messages.last
    puts "\nWhoops! Try again."
    console.last_command_errored = false
  end
  
  def tick_evals
    state.evals ||= []
    if console.last_command && (console.last_command.start_with?("outputs.") || console.last_command.start_with?("state."))
      state.evals << console.last_command
      console.last_command = nil
    end
  
    state.evals.each do |l|
      Kernel.eval l
    end
  rescue Exception => e
    state.evals = state.evals[0..-2]
  end
  
  $tutorial_outputs ||= TutorialOutputs.new
  
  def tick args
    $gtk.log_level = :off
    defaults
    console.show
    $tutorial_outputs.clear
    $tutorial_outputs.solids  << [900, 37, 480, 700,   0,   0,   0, 255]
    $tutorial_outputs.borders << [900, 37, 380, 683, 255, 255, 255]
    tick_evals
    $tutorial_outputs.tick
    tick_intro
    tick_hello_dragonruby
    tick_reset_button
    tick_explain_solid
    tick_explain_solid_blue
    tick_reprint_on_error
    tick_explain_tick_count
    tick_explain_mod
    tick_explain_string_interpolation
  end
  
  def console
    $gtk.console
  end
  
  def queue_message message
    $gtk.args.state.messages ||= []
    return if $gtk.args.state.messages.include? message
    $gtk.args.state.messages << message
    last_three = [$gtk.console.log[-3], $gtk.console.log[-2], $gtk.console.log[-1]].reject_nil
    $gtk.console.log.clear
    puts seperator
    $gtk.console.log += last_three
    puts seperator
    puts message
    puts seperator
  end
  
  def console_has? message, not_message = nil
    console.log
           .map(&:upcase)
           .reject { |s| not_message && s.include?(not_message.upcase) }
           .any?   { |s| s.include?("#{message.upcase}") }
  end
  
  def restart_tutorial
    $tutorial_outputs.clear
    $gtk.console.log.clear
    $gtk.reset
    puts "Starting the tutorial over!"
  end
  
  def state
    $gtk.args.state
  end
  
  def inputs
    $gtk.args.inputs
  end
  
  def outputs
    $tutorial_outputs
  end

#+end_src

*** Learn Ruby Optional - Intermediate Ruby Primer - printing.txt
#+begin_src ruby
  # ./samples/00_learn_ruby_optional/00_intermediate_ruby_primer/app/01_printing.txt
  # ====================================================================================
  # Commenting Code
  # ====================================================================================
  #
  # Prefixing text with a pound sign (#) is how you comment code in Ruby. Example:
  #
  # I am commented code. And so are the lines above.
  #
  # I you want more than a quick primer on Ruby, check out https://poignant.guide/. It's
  # an entertaining read. Otherwise, go to the next txt file.
  #
  # Follow along by visiting:
  # https://s3.amazonaws.com/s3.dragonruby.org/dragonruby-gtk-intermediate.mp4
  
  # ====================================================================================
  #  Printing to the Console:
  # ====================================================================================
  #
  # Every time you save repl.rb file, DragonRuby runs the code within it. Copy this text
  # to repl.rb and save to see Hello World printed to the console.
  
  repl do
    puts '* RUBY PRIMER: Printing to the console using the ~puts~ function.'
    puts '===='
    puts '======'
    puts '================================'
    puts 'Hello World'
    puts '================================'
    puts '======'
    puts '===='
  end

#+end_src

*** Learn Ruby Optional - Intermediate Ruby Primer - strings.txt
#+begin_src ruby
  # ./samples/00_learn_ruby_optional/00_intermediate_ruby_primer/app/02_strings.txt
  # ====================================================================================
  #  Strings
  # ====================================================================================
  #
  # Here is how you work with strings in Ruby. Take the text
  # in this file and paste it into repl.rb and save:
  
  repl do
    puts '* RUBY PRIMER: strings'
    message = "Hello World"
    puts "The value of message is: " + message
    puts "Any value can be interpolated within a string using \#{}."
    puts "Interpolated message: #{message}."
    puts 'This #{message} is not interpolated because the string uses single quotes.'
  end

#+end_src

*** Learn Ruby Optional - Intermediate Ruby Primer - numbers.txt
#+begin_src ruby
  # ./samples/00_learn_ruby_optional/00_intermediate_ruby_primer/app/03_numbers.txt
  # ====================================================================================
  #  Numerics
  # ====================================================================================
  #
  # Here is how you work with numbers in Ruby. Take the text
  # in this file and paste it into repl.rb and save:
  
  repl do
    puts '* RUBY PRIMER: Fixnum and Floats'
    a = 10
    puts "The value of a is: #{a}"
    puts "a + 1 is: #{a + 1}"
    puts "a / 3 is: #{a / 3}"
    puts ''
  
    b = 10.12
    puts "The value of b is: #{b}"
    puts "b + 1 is: #{b + 1}"
    puts "b as an integer is: #{b.to_i}"
    puts ''
  end

#+end_src

*** Learn Ruby Optional - Intermediate Ruby Primer - booleans.txt
#+begin_src ruby
  # ./samples/00_learn_ruby_optional/00_intermediate_ruby_primer/app/04_booleans.txt
  # ====================================================================================
  #  Booleans
  # ====================================================================================
  #
  # Here is how you work with numbers in Ruby. Take the text
  # in this file and paste it into repl.rb and save:
  
  repl do
    puts '* RUBY PRIMER: TrueClass, FalseClass, NilClass (truthy / falsey values)'
    puts "Anything that *isn't* false or nil is true."
  
    c = 30
    puts "The value of c is #{c}."
  
    if c
      puts "This if statement ran because c is truthy."
    end
  
    d = false
    puts "The value if d is #{d}. The type for d is #{d.class}."
  
    if !d
      puts "This if statement ran because d is falsey, using the not operator (!)."
    end
  
    e = nil
    puts "Nil is also considered falsey. The value of e is: #{e} (a blank string when printed). Which is of type #{e.class}."
  
    if !e
      puts "This if statement ran because e is nil and the if statement applied the NOT operator. !e yields a type of #{(!e).class}."
    end
  end

#+end_src

*** Learn Ruby Optional - Intermediate Ruby Primer - conditionals.txt
#+begin_src ruby
  # ./samples/00_learn_ruby_optional/00_intermediate_ruby_primer/app/05_conditionals.txt
  # ====================================================================================
  #  Conditionals
  # ====================================================================================
  #
  # Here is how you create conditionals in Ruby. Take the text
  # in this file and paste it into repl.rb and save:
  
  repl do
    puts "* RUBY PRIMER: Conditionals"
  end
  
  # ====================================================================================
  #  if
  # ====================================================================================
  
  repl do
    puts "** INFO: if statement"
    i_am_one = 1
    if i_am_one
      puts "This was printed because i_am_one is truthy."
    end
  end
  
  # ====================================================================================
  #  if/else
  # ====================================================================================
  
  repl do
    puts "** INFO: if/else statement"
    i_am_false = false
    if i_am_false
      puts "This will NOT get printed because i_am_false is false."
    else
      puts "This was printed because i_am_false is false."
    end
  end
  
  
  # ====================================================================================
  #  if/elsif/else
  # ====================================================================================
  
  repl do
    puts "** INFO: if/elsif/else statement"
    i_am_false = false
    i_am_true  = true
    if i_am_false
      puts "This will NOT get printed because i_am_false is false."
    elsif i_am_true
      puts "This was printed because i_am_true is true."
    else
      puts "This will NOT get printed i_am_true was true."
    end
  end
  
  # ====================================================================================
  #  case
  # ====================================================================================
  
  repl do
    puts "** INFO case statement"
    i_am_one = 1 # change this value to see different results
  
    case i_am_one
    when 10
      puts "the value of i_am_one is 10"
    when 9
      puts "the value of i_am_one is 9"
    when 5
      puts "the value of i_am_one is 5"
    when 1
      puts "the value of i_am_one is 1"
    else
      puts "Value wasn't cased."
    end
  end
  
  # ====================================================================================
  #  comparison operators
  # ====================================================================================
  
  repl do
    puts "** INFO: Different types of comparisons"
    if 4 == 4
      puts "4 equals 4 (==)"
    end
  
    if 4 != 3
      puts "4 does not equal 3 (!=)"
    end
  
    if 3 < 4
      puts "3 is less than 4 (<)"
    end
  
    if 4 > 3
      puts "4 is greater than 3 (>)"
    end
  end
  
  # ====================================================================================
  #  and/or conditionals
  # ====================================================================================
  
  repl do
    puts "** INFO: AND, OR operator (&&, ||)"
    if (4 > 3) || (3 < 4) || false
      puts "print this if 4 is greater than 3 OR 3 is less than 4 OR false is true (||)"
    end
  
    if (4 > 3) && (3 < 4)
      puts "print this if 4 is greater than 3 AND 3 is less than 4 (&&)"
    end
  end

#+end_src

*** Learn Ruby Optional - Intermediate Ruby Primer - looping.txt
#+begin_src ruby
  # ./samples/00_learn_ruby_optional/00_intermediate_ruby_primer/app/06_looping.txt
  # ====================================================================================
  #  Looping
  # ====================================================================================
  #
  # Looping looks a whole lot different than other languages.
  # But it's pretty awesome when you get used to it.
  
  repl do
    puts "* RUBY PRIMER: Loops"
  end
  
  # ====================================================================================
  #  times
  # ====================================================================================
  
  repl do
    puts "** INFO: ~Numeric#times~ (for loop)"
    3.times do |i|
      puts i
    end
  end
  
  # ====================================================================================
  #  foreach
  # ====================================================================================
  
  repl do
    puts "** INFO: ~Array#each~ (for each loop)"
    array = ["a", "b", "c", "d"]
    array.each do |char|
      puts char
    end
  
    puts "** INFO: ~Array#each_with_index~ (for each loop)"
    array = ["a", "b", "c", "d"]
    array.each do |char, i|
      puts "index #{i}: #{char}"
    end
  end
  
  # ====================================================================================
  #  ranges
  # ====================================================================================
  
  repl do
    puts "** INFO: range block exclusive (three dots)"
    (0...3).each do |i|
      puts i
    end
  
    puts "** INFO: range block inclusive (two dots)"
    (0..3).each do |i|
      puts i
    end
  end

#+end_src

*** Learn Ruby Optional - Intermediate Ruby Primer - functions.txt
#+begin_src ruby
  # ./samples/00_learn_ruby_optional/00_intermediate_ruby_primer/app/07_functions.txt
  # ====================================================================================
  # Functions
  # ====================================================================================
  
  # The last statement of a function is implictly returned. Parenthesis for functions
  # are optional as long as the statement can be envaluated disambiguously.
  
  repl do
    puts "* RUBY PRIMER: Functions"
  end
  
  # ====================================================================================
  # Functions single parameter
  # ====================================================================================
  
  repl do
    puts "* INFO: Function with one parameter"
  
    # function definition
    def add_one_to n
      n + 1
    end
  
    # Parenthesis are optional in Ruby as long as the
    # parsing is disambiguous. Here are a couple of variations.
    # Generally speaking, don't put parenthesis is you don't have to.
  
    # Conventional Usage of Parenthesis.
    puts add_one_to(3)
  
    # DragonRuby's recommended use of parenthesis (inner function has parenthesis).
    puts (add_one_to 3)
  
    # Full parens.
    puts(add_one_to(3))
  
    # Outer function has parenthesis
    puts(add_one_to 3)
  end
  
  # ====================================================================================
  # Functions with default parameter values
  # ====================================================================================
  
  repl do
    puts "* INFO: Function with default value"
    def function_with_default_value v = 10
      v * 10
    end
  
    puts "Passing the argument three yields: #{function_with_default_value 3}"
    puts "Passing no argument yields: #{function_with_default_value}"
  end
  
  # ====================================================================================
  # Nil default parameter value and ||= operator.
  # ====================================================================================
  
  repl do
    puts "* INFO: Using the OR EQUAL operator (||=)"
    def function_with_nil_default_with_local a = nil
      result   = a
      result ||= "DEFAULT_VALUE_OF_A_IS_NIL_OR_FALSE"
      "value is #{result}."
    end
  
    puts "Passing 'hi' as the argument yields: #{function_with_nil_default_with_local 'hi'}"
    puts "Passing nil: #{function_with_nil_default_with_local}"
  end

#+end_src

*** Learn Ruby Optional - Intermediate Ruby Primer - arrays.txt
#+begin_src ruby
  # ./samples/00_learn_ruby_optional/00_intermediate_ruby_primer/app/08_arrays.txt
  # ====================================================================================
  # Arrays
  # ====================================================================================
  
  # Arrays are incredibly powerful in Ruby. Learn to use them well.
  
  repl do
    puts "* RUBY PRIMER: ARRAYS"
  end
  
  # ====================================================================================
  # Enumerable ranges and .to_a
  # ====================================================================================
  
  repl do
    puts "** INFO: Create an array with the numbers 1 to 10."
    one_to_ten = (1..10).to_a
    puts one_to_ten
  end
  
  # ====================================================================================
  # Finding elements
  # ====================================================================================
  
  repl do
    puts "** INFO: Finding elements in an array using ~Array#find_all~."
    puts "Create a new array that only contains even numbers from the previous array."
  
    one_to_ten = (1..10).to_a
    evens = one_to_ten.find_all do |number|
      number % 2 == 0
    end
  
    puts evens
  end
  
  # ====================================================================================
  # Rejecting elements
  # ====================================================================================
  
  repl do
    puts "** INFO: Removing elements in an array using ~Array#reject~."
    puts "Create a new array that rejects odd numbers."
  
    one_to_ten = (1..10).to_a
    also_even = one_to_ten.reject do |number|
      number % 2 != 0
    end
  
    puts also_even
  end
  
  # ====================================================================================
  # Array transform using the map function.
  # ====================================================================================
  
  repl do
    puts "** INFO: Creating new derived values from an array using ~Array#map~."
    puts "Create an array that doubles every number."
  
    one_to_ten = (1..10).to_a
    doubled = one_to_ten.map do |number|
      number * 2
    end
  
    puts doubled
  end
  
  # ====================================================================================
  # Combining array functions.
  # ====================================================================================
  
  repl do
    puts "** INFO: Combining ~Array#find_all~ along with ~Array#map~."
    puts "Create an array that selects only odd numbers and then multiply those by 10."
  
    one_to_ten = (1..10).to_a
    odd_doubled = one_to_ten.find_all do |number|
      number % 2 != 0
    end.map do |odd_number|
      odd_number * 10
    end
  
    puts odd_doubled
  end
  
  # ====================================================================================
  # Product function.
  # ====================================================================================
  
  repl do
    puts "** INFO: Create all combinations of array values using ~Array#product~."
    puts "All two-item pairs of numbers 1 to 10."
    one_to_ten = (1..10).to_a
    all_combinations = one_to_ten.product(one_to_ten)
    puts all_combinations
  end
  
  # ====================================================================================
  # Uniq and sort function.
  # ====================================================================================
  
  repl do
    puts "** INFO: Providing uniq values using ~Array#uniq~ and ~Array#sort~."
    puts "All uniq combinations of numbers regardless of order."
    puts "For example: [1, 2] is the same as [2, 1]."
    one_to_ten = (1..10).to_a
    uniq_combinations =
      one_to_ten.product(one_to_ten)
                .map do |unsorted_number|
                  unsorted_number.sort
                end.uniq
    puts uniq_combinations
  end
  
  # ====================================================================================
  # Example of an advanced array transform.
  # ====================================================================================
  
  repl do
    puts "** INFO: Advanced chaining. Combining ~Array's ~map~, ~find_all~, ~sort~, and ~sort_by~."
    puts "All unique Pythagorean Triples between 1 and 100 sorted by area of the triangle."
  
    one_to_hundred = (1..100).to_a
  
    triples =
      one_to_hundred.product(one_to_hundred).map do |width, height|
                  [width, height, Math.sqrt(width ** 2 + height ** 2)]
                end.find_all do |_, _, hypotenuse|
                  hypotenuse.to_i == hypotenuse
                end.map do |triangle|
                  triangle.map(&:to_i)
                end.uniq do |triangle|
                  triangle.sort
                end.map do |width, height, hypotenuse|
                  [width, height, hypotenuse, (width * height) / 2]
                end.sort_by do |_, _, _, area|
                  area
                end
  
    triples.each do |width, height, hypotenuse, _|
      puts "(#{width}, #{height}, #{hypotenuse})"
    end
  end
  
  # ====================================================================================
  # Example of an sorting.
  # ====================================================================================
  
  repl do
    puts "** INFO: Implementing a custom sort function that operates on the ~Hash~ datatype."
  
    things_to_sort = [
      { type: :background, order: 1 },
      { type: :foreground, order: 1 },
      { type: :foreground, order: 2 }
    ]
    puts "*** Original array."
    puts things_to_sort
  
    puts "*** Simple sort using key."
    # For a simple sort, you can use sort_by
    results = things_to_sort.sort_by do |hash|
      hash[:order]
    end
  
    puts results
  
    puts "*** Custom sort."
    puts "**** Sorting process."
    # for a more complicated sort, you can provide a block that returns
    # -1, 0, 1 for a left and right operand
    results = things_to_sort.sort do |l, r|
      sort_result = 0
      puts "here is l: #{l}"
      puts "here is r: #{r || "nil"}"
      # if either value is nil/false return 0
      if !l || !r
        sort_result = 0
      # if the type of "left" is background and the
      # type of "right" is foreground, then return
      # -1 (which means "left" is less than "right"
      elsif l[:type] == :background && r[:type] == :foreground
        sort_result = -1
      # if the type of "left" is foreground and the
      # type of "right" is background, then return
      #  1 (which means "left" is greater than "right"
      elsif l[:type] == :foreground && r[:type] == :background
        sort_result = 1
      # if "left" and "right"'s type are the same, then
      # use the order as the tie breaker
      elsif l[:order] < r[:order]
        sort_result = -1
      elsif l[:order] > r[:order]
        sort_result = 1
      # returning 0 means both values are equal
      else
        sort_result = 0
      end
      sort_result
    end.to_a
  
    puts "**** Sort result."
    puts results
  end
  
  # ====================================================================================
  # Api documention for Array that is worth commiting to memory because arrays are so
  # awesome in Ruby: https://docs.ruby-lang.org/en/2.0.0/Array.html
  # ====================================================================================

#+end_src

*** Learn Ruby Optional - Intermediate Ruby Primer - main.rb
#+begin_src ruby
  # ./samples/00_learn_ruby_optional/00_intermediate_ruby_primer/app/main.rb
  def tick args
    args.outputs.labels << [640, 380, "Open repl.rb in the text editor of your choice and follow the document.", 0, 1]
  end

#+end_src

*** Rendering Basics - Labels - main.rb
#+begin_src ruby
  # ./samples/01_rendering_basics/01_labels/app/main.rb
  =begin
  
  APIs listing that haven't been encountered in a previous sample apps:
  
  - args.outputs.labels: An array. Values in this array generate labels
    the screen.
  - args.grid.(left|right|top|bottom): Pixel value for the boundaries of the virtual
    720 p screen (Dragon Ruby Game Toolkits's virtual resolution is always 1280x720).
  - Numeric#shift_(left|right|up|down): Shifts the Numeric in the correct direction
    by adding or subracting.
  
  =end
  
  # Labels are used to represent text elements in DragonRuby
  
  # An example of creating a label is:
  # args.outputs.labels << [320, 640, "Example", 3, 1, 255, 0, 0, 200, manaspace.ttf]
  
  # The code above does the following:
  # 1. GET the place where labels go: args.outputs.labels
  # 2. Request a new LABEL be ADDED: <<
  # 3. The DEFINITION of a SOLID is the ARRAY:
  #     [320, 640, "Example", 3,     1,   255,   0,    0,    200,  manaspace.ttf]
  #     [ X ,  Y,    TEXT,   SIZE, ALIGN, RED, GREEN, BLUE, ALPHA, FONT STYLE]
  
  
  # The tick method is called by DragonRuby every frame
  # args contains all the information regarding the game.
  def tick args
    tick_instructions args, "Sample app shows different version of label sizes and alignments. And how to use hashes instead of arrays."
    # Here are some examples of simple labels, with the minimum number of parameters
    # Note that the default values for the other parameters are 0, except for Alpha which is 255 and Font Style which is the default font
    args.outputs.labels << [400, 620, "Here is a label with just an x, y, and text"]
  
    args.outputs.labels << [args.grid.left.shift_right(5), args.grid.top.shift_down(5), "This is a label located at the top left."]
    args.outputs.labels << [args.grid.left.shift_right(5), args.grid.bottom.shift_up(30), "This is a label located at the bottom left."]
    args.outputs.labels << [args.grid.right.shift_left(420), args.grid.top.shift_down(5), "This is a label located at the top right."]
    args.outputs.labels << [args.grid.right.shift_left(440), args.grid.bottom.shift_up(30), "This is a label located at the bottom right."]
  
    # Demonstration of the Size Parameter
    args.outputs.labels << [175 + 150, 610 - 50, "Smaller label.",  -2]
    args.outputs.labels << [175 + 150, 580 - 50, "Small label.",    -1]
    args.outputs.labels << [175 + 150, 550 - 50, "Medium label.",    0]
    args.outputs.labels << [175 + 150, 520 - 50, "Large label.",     1]
    args.outputs.labels << [175 + 150, 490 - 50, "Larger label.",    2]
  
    # Demonstration of the Align Parameter
    args.outputs.labels << [260 + 150, 345 - 50, "Left aligned.",    0, 2]
    args.outputs.labels << [260 + 150, 325 - 50, "Center aligned.",  0, 1]
    args.outputs.labels << [260 + 150, 305 - 50, "Right aligned.",   0, 0]
  
    # Demonstration of the RGBA parameters
    args.outputs.labels << [600  + 150, 590 - 50, "Red Label.",       0, 0, 255,   0,   0]
    args.outputs.labels << [600  + 150, 570 - 50, "Green Label.",     0, 0,   0, 255,   0]
    args.outputs.labels << [600  + 150, 550 - 50, "Blue Label.",      0, 0,   0,   0, 255]
    args.outputs.labels << [600  + 150, 530 - 50, "Faded Label.",     0, 0,   0,   0,   0, 128]
  
    # Demonstration of the Font parameter
    # In order to use a font of your choice, add its ttf file to the project folder, where the app folder is
    args.outputs.labels << [690 + 150, 330 - 20, "Custom font (Array)", 0, 1, 125, 0, 200, 255, "manaspc.ttf" ]
    args.outputs.primitives << { x: 690 + 150,
                                 y: 330 - 50,
                                 text: "Custom font (Hash)",
                                 size_enum: 0,
                                 alignment_enum: 1,
                                 r: 125,
                                 g: 0,
                                 b: 200,
                                 a: 255,
                                 font: "manaspc.ttf" }.label!
  
    # Primitives can hold anything, and can be given a label in the following forms
    args.outputs.primitives << [690 + 150, 330 - 80, "Custom font (.primitives Array)", 0, 1, 125, 0, 200, 255, "manaspc.ttf" ].label
  
    args.outputs.primitives << { x: 690 + 150,
                                 y: 330 - 110,
                                 text: "Custom font (.primitives Hash)",
                                 size_enum: 0,
                                 alignment_enum: 1,
                                 r: 125,
                                 g: 0,
                                 b: 200,
                                 a: 255,
                                 font: "manaspc.ttf" }.label!
  end
  
  def tick_instructions args, text, y = 715
    return if args.state.key_event_occurred
    if args.inputs.mouse.click ||
       args.inputs.keyboard.directional_vector ||
       args.inputs.keyboard.key_down.enter ||
       args.inputs.keyboard.key_down.escape
      args.state.key_event_occurred = true
    end
  
    args.outputs.debug << [0, y - 50, 1280, 60].solid
    args.outputs.debug << [640, y, text, 1, 1, 255, 255, 255].label
    args.outputs.debug << [640, y - 25, "(click to dismiss instructions)" , -2, 1, 255, 255, 255].label
  end

#+end_src

*** Rendering Basics - Lines - main.rb
#+begin_src ruby
  # ./samples/01_rendering_basics/02_lines/app/main.rb
  =begin
  
  APIs listing that haven't been encountered in a previous sample apps:
  
  - args.outputs.lines: An array. Values in this array generate lines on
    the screen.
  - args.state.tick_count: This property contains an integer value that
    represents the current frame. GTK renders at 60 FPS. A value of 0
    for args.state.tick_count represents the initial load of the game.
  
  =end
  
  # The parameters required for lines are:
  # 1. The initial point (x, y)
  # 2. The end point (x2, y2)
  # 3. The rgba values for the color and transparency (r, g, b, a)
  
  # An example of creating a line would be:
  # args.outputs.lines << [100, 100, 300, 300, 255, 0, 255, 255]
  
  # This would create a line from (100, 100) to (300, 300)
  # The RGB code (255, 0, 255) would determine its color, a purple
  # It would have an Alpha value of 255, making it completely opaque
  
  def tick args
    tick_instructions args, "Sample app shows how to create lines."
  
    args.outputs.labels << [480, 620, "Lines (x, y, x2, y2, r, g, b, a)"]
  
    # Some simple lines
    args.outputs.lines  << [380, 450, 675, 450]
    args.outputs.lines  << [380, 410, 875, 410]
  
    # These examples utilize args.state.tick_count to change the length of the lines over time
    # args.state.tick_count is the ticks that have occurred in the game
    # This is accomplished by making either the starting or ending point based on the args.state.tick_count
    args.outputs.lines  << [380, 370, 875, 370, args.state.tick_count % 255, 0, 0, 255]
    args.outputs.lines  << [380, 330 - args.state.tick_count % 25, 875, 330, 0, 0, 0, 255]
    args.outputs.lines  << [380 + args.state.tick_count % 400, 290, 875, 290, 0, 0, 0, 255]
  end
  
  def tick_instructions args, text, y = 715
    return if args.state.key_event_occurred
    if args.inputs.mouse.click ||
       args.inputs.keyboard.directional_vector ||
       args.inputs.keyboard.key_down.enter ||
       args.inputs.keyboard.key_down.escape
      args.state.key_event_occurred = true
    end
  
    args.outputs.debug << [0, y - 50, 1280, 60].solid
    args.outputs.debug << [640, y, text, 1, 1, 255, 255, 255].label
    args.outputs.debug << [640, y - 25, "(click to dismiss instructions)" , -2, 1, 255, 255, 255].label
  end

#+end_src

*** Rendering Basics - Solids Borders - main.rb
#+begin_src ruby
  # ./samples/01_rendering_basics/03_solids_borders/app/main.rb
  =begin
  
  APIs listing that haven't been encountered in a previous sample apps:
  
  - args.outputs.solids: An array. Values in this array generate
    solid/filled rectangles on the screen.
  
  =end
  
  # Rects are outputted in DragonRuby as rectangles
  # If filled in, they are solids
  # If hollow, they are borders
  
  # Solids are added to args.outputs.solids
  # Borders are added to args.outputs.borders
  
  # The parameters required for rects are:
  # 1. The upper right corner (x, y)
  # 2. The width (w)
  # 3. The height (h)
  # 4. The rgba values for the color and transparency (r, g, b, a)
  
  # Here is an example of a rect definition:
  # [100, 100, 400, 500, 0, 255, 0, 180]
  
  # The example would create a rect from (100, 100)
  # Extending 400 pixels across the x axis
  # and 500 pixels across the y axis
  # The rect would be green (0, 255, 0)
  # and mostly opaque with some transparency (180)
  
  # Whether the rect would be filled or not depends on if
  # it is added to args.outputs.solids or args.outputs.borders
  
  
  def tick args
    tick_instructions args, "Sample app shows how to create solid squares."
    args.outputs.labels << [460, 600, "Solids (x, y, w, h, r, g, b, a)"]
    args.outputs.solids << [470, 520, 50, 50]
    args.outputs.solids << [530, 520, 50, 50, 0, 0, 0]
    args.outputs.solids << [590, 520, 50, 50, 255, 0, 0]
    args.outputs.solids << [650, 520, 50, 50, 255, 0, 0, 128]
    args.outputs.solids << [710, 520, 50, 50, 0, 0, 0, 128 + args.state.tick_count % 128]
  
  
    args.outputs.labels <<  [460, 400, "Borders (x, y, w, h, r, g, b, a)"]
    args.outputs.borders << [470, 320, 50, 50]
    args.outputs.borders << [530, 320, 50, 50, 0, 0, 0]
    args.outputs.borders << [590, 320, 50, 50, 255, 0, 0]
    args.outputs.borders << [650, 320, 50, 50, 255, 0, 0, 128]
    args.outputs.borders << [710, 320, 50, 50, 0, 0, 0, 128 + args.state.tick_count % 128]
  end
  
  def tick_instructions args, text, y = 715
    return if args.state.key_event_occurred
    if args.inputs.mouse.click ||
       args.inputs.keyboard.directional_vector ||
       args.inputs.keyboard.key_down.enter ||
       args.inputs.keyboard.key_down.escape
      args.state.key_event_occurred = true
    end
  
    args.outputs.debug << [0, y - 50, 1280, 60].solid
    args.outputs.debug << [640, y, text, 1, 1, 255, 255, 255].label
    args.outputs.debug << [640, y - 25, "(click to dismiss instructions)" , -2, 1, 255, 255, 255].label
  end

#+end_src

*** Rendering Basics - Sprites - main.rb
#+begin_src ruby
  # ./samples/01_rendering_basics/04_sprites/app/main.rb
  =begin
  
  APIs listing that haven't been encountered in a previous sample apps:
  
  - args.outputs.sprites: An array. Values in this array generate
    sprites on the screen. The location of the sprite is assumed to
    be under the mygame/ directory (the exception being dragonruby.png).
  
  =end
  
  
  # For all other display outputs, Sprites are your solution
  # Sprites import images and display them with a certain rectangular area
  # The image can be of any usual format and should be located within the folder,
  # similar to additional fonts.
  
  # Sprites have the following parameters
  # Rectangular area (x, y, width, height)
  # The image (path)
  # Rotation (angle)
  # Alpha (a)
  
  def tick args
    tick_instructions args, "Sample app shows how to render a sprite. Set its alpha, and rotate it."
    args.outputs.labels <<  [460, 600, "Sprites (x, y, w, h, path, angle, a)"]
    args.outputs.sprites << [460, 470, 128, 101, 'dragonruby.png']
    args.outputs.sprites << [610, 470, 128, 101, 'dragonruby.png', args.state.tick_count % 360]
    args.outputs.sprites << [760, 470, 128, 101, 'dragonruby.png', 0, args.state.tick_count % 255]
  end
  
  def tick_instructions args, text, y = 715
    return if args.state.key_event_occurred
    if args.inputs.mouse.click ||
       args.inputs.keyboard.directional_vector ||
       args.inputs.keyboard.key_down.enter ||
       args.inputs.keyboard.key_down.escape
      args.state.key_event_occurred = true
    end
  
    args.outputs.debug << [0, y - 50, 1280, 60].solid
    args.outputs.debug << [640, y, text, 1, 1, 255, 255, 255].label
    args.outputs.debug << [640, y - 25, "(click to dismiss instructions)" , -2, 1, 255, 255, 255].label
  end

#+end_src

*** Rendering Basics - Sounds - main.rb
#+begin_src ruby
  # ./samples/01_rendering_basics/05_sounds/app/main.rb
  =begin
  
   APIs Listing that haven't been encountered in previous sample apps:
  
   - sample: Chooses random element from array.
     In this sample app, the target note is set by taking a sample from the collection
     of available notes.
  
   Reminders:
  
   - String interpolation: Uses #{} syntax; everything between the #{ and the } is evaluated
     as Ruby code, and the placeholder is replaced with its corresponding value or result.
  
   - args.outputs.labels: An array. The values generate a label.
     The parameters are [X, Y, TEXT, SIZE, ALIGNMENT, RED, GREEN, BLUE, ALPHA, FONT STYLE]
     For more information about labels, go to mygame/documentation/02-labels.md.
  =end
  
  # This sample app allows users to test their musical skills by matching the piano sound that plays in each
  # level to the correct note.
  
  # Runs all the methods necessary for the game to function properly.
  def tick args
    args.outputs.labels << [640, 360, "Click anywhere to play a random sound.", 0, 1]
    args.state.notes ||= [:C3, :D3, :E3, :F3, :G3, :A3, :B3, :C4]
  
    if args.inputs.mouse.click
      # Play a sound by adding a string to args.outputs.sounds
      args.outputs.sounds << "sounds/#{args.state.notes.sample}.wav" # sound of target note is output
    end
  end

#+end_src

*** Input Basics - Keyboard - main.rb
#+begin_src ruby
  # ./samples/02_input_basics/01_keyboard/app/main.rb
  =begin
  
  APIs listing that haven't been encountered in a previous sample apps:
  
  - args.inputs.keyboard.key_up.KEY: The value of the properties will be set
    to the frame  that the key_up event occurred (the frame correlates
    to args.state.tick_count). Otherwise the value will be nil. For a
    full listing of keys, take a look at mygame/documentation/06-keyboard.md.
  - args.state.PROPERTY: The state property on args is a dynamic
    structure. You can define ANY property here with ANY type of
    arbitrary nesting. Properties defined on args.state will be retained
    across frames. If you attempt access a property that doesn't exist
    on args.state, it will simply return nil (no exception will be thrown).
  
  =end
  
  # Along with outputs, inputs are also an essential part of video game development
  # DragonRuby can take input from keyboards, mouse, and controllers.
  # This sample app will cover keyboard input.
  
  # args.inputs.keyboard.key_up.a will check to see if the a key has been pressed
  # This will work with the other keys as well
  
  
  def tick args
    tick_instructions args, "Sample app shows how keyboard events are registered and accessed.", 360
    # Notice how small_font accounts for all the remaining parameters
    args.outputs.labels << { x: 460, y: row_to_px(args, 0), text: "Current game time: #{args.state.tick_count}", size_enum: -1 }
    args.outputs.labels << { x: 460, y: row_to_px(args, 2), text: "Keyboard input: args.inputs.keyboard.key_up.h", size_enum: -1 }
    args.outputs.labels << { x: 460, y: row_to_px(args, 3), text: "Press \"h\" on the keyboard.", size_enum: -1 }
  
    # Input on a specifc key can be found through args.inputs.keyboard.key_up followed by the key
    if args.inputs.keyboard.key_up.h
      args.state.h_pressed_at = args.state.tick_count
    end
  
    # This code simplifies to if args.state.h_pressed_at has not been initialized, set it to false
    args.state.h_pressed_at ||= false
  
    if args.state.h_pressed_at
      args.outputs.labels << { x: 460, y: row_to_px(args, 4), text: "\"h\" was pressed at time: #{args.state.h_pressed_at}", size_enum: -1 }
    else
      args.outputs.labels << { x: 460, y: row_to_px(args, 4), text: "\"h\" has never been pressed.", size_enum: -1 }
    end
  
    tick_help_text args
  end
  
  def row_to_px args, row_number, y_offset = 20
    # This takes a row_number and converts it to pixels DragonRuby understands.
    # Row 0 starts 5 units below the top of the grid
    # Each row afterward is 20 units lower
    args.grid.top - 5 - (y_offset * row_number)
  end
  
  # Don't worry about understanding the code within this method just yet.
  # This method shows you the help text within the game.
  def tick_help_text args
    return unless args.state.h_pressed_at
  
    args.state.key_value_history      ||= {}
    args.state.key_down_value_history ||= {}
    args.state.key_held_value_history ||= {}
    args.state.key_up_value_history   ||= {}
  
    if (args.inputs.keyboard.key_down.truthy_keys.length > 0 ||
        args.inputs.keyboard.key_held.truthy_keys.length > 0 ||
        args.inputs.keyboard.key_up.truthy_keys.length > 0)
      args.state.help_available = true
      args.state.no_activity_debounce = nil
    else
      args.state.no_activity_debounce ||= 5.seconds
      args.state.no_activity_debounce -= 1
      if args.state.no_activity_debounce <= 0
        args.state.help_available = false
        args.state.key_value_history        = {}
        args.state.key_down_value_history   = {}
        args.state.key_held_value_history   = {}
        args.state.key_up_value_history     = {}
      end
    end
  
    args.outputs.labels << { x: 10, y: row_to_px(args, 6), text: "This is the api for the keys you've pressed:", size_enum: -1, r: 180 }
  
    if !args.state.help_available
      args.outputs.labels << [10, row_to_px(args, 7),  "Press a key and I'll show code to access the key and what value will be returned if you used the code.", small_font]
      return
    end
  
    args.outputs.labels << { x: 10 , y: row_to_px(args, 7), text: "args.inputs.keyboard",          size_enum: -2 }
    args.outputs.labels << { x: 330, y: row_to_px(args, 7), text: "args.inputs.keyboard.key_down", size_enum: -2 }
    args.outputs.labels << { x: 650, y: row_to_px(args, 7), text: "args.inputs.keyboard.key_held", size_enum: -2 }
    args.outputs.labels << { x: 990, y: row_to_px(args, 7), text: "args.inputs.keyboard.key_up",   size_enum: -2 }
  
    fill_history args, :key_value_history,      :down_or_held, nil
    fill_history args, :key_down_value_history, :down,        :key_down
    fill_history args, :key_held_value_history, :held,        :key_held
    fill_history args, :key_up_value_history,   :up,          :key_up
  
    render_help_labels args, :key_value_history,      :down_or_held, nil,      10
    render_help_labels args, :key_down_value_history, :down,        :key_down, 330
    render_help_labels args, :key_held_value_history, :held,        :key_held, 650
    render_help_labels args, :key_up_value_history,   :up,          :key_up,   990
  end
  
  def fill_history args, history_key, state_key, keyboard_method
    fill_single_history args, history_key, state_key, keyboard_method, :raw_key
    fill_single_history args, history_key, state_key, keyboard_method, :char
    args.inputs.keyboard.keys[state_key].each do |key_name|
      fill_single_history args, history_key, state_key, keyboard_method, key_name
    end
  end
  
  def fill_single_history args, history_key, state_key, keyboard_method, key_name
    current_value = args.inputs.keyboard.send(key_name)
    if keyboard_method
      current_value = args.inputs.keyboard.send(keyboard_method).send(key_name)
    end
    args.state.as_hash[history_key][key_name] ||= []
    args.state.as_hash[history_key][key_name] << current_value
    args.state.as_hash[history_key][key_name] = args.state.as_hash[history_key][key_name].reverse.uniq.take(3).reverse
  end
  
  def render_help_labels args, history_key, state_key, keyboard_method, x
    idx = 8
    args.outputs.labels << args.state
                             .as_hash[history_key]
                             .keys
                             .reverse
                             .map
                             .with_index do |k, i|
      v = args.state.as_hash[history_key][k]
      current_value = args.inputs.keyboard.send(k)
      if keyboard_method
        current_value = args.inputs.keyboard.send(keyboard_method).send(k)
      end
      idx += 2
      [
        { x: x, y: row_to_px(args, idx + 0, 16), text: "    .#{k} is #{current_value || "nil"}", size_enum: -2 },
        { x: x, y: row_to_px(args, idx + 1, 16), text: "       was #{v}", size_enum: -2 }
      ]
    end
  end
  
  
  def tick_instructions args, text, y = 715
    return if args.state.key_event_occurred
    if args.inputs.mouse.click ||
       args.inputs.keyboard.directional_vector ||
       args.inputs.keyboard.key_down.enter ||
       args.inputs.keyboard.key_down.escape
      args.state.key_event_occurred = true
    end
  
    args.outputs.debug << { x: 0,   y: y - 50, w: 1280, h: 60 }.solid!
    args.outputs.debug << { x: 640, y: y,      text: text,
                            size_enum: 1, alignment_enum: 1, r: 255, g: 255, b: 255 }.label!
    args.outputs.debug << { x: 640, y: y - 25, text: "(click to dismiss instructions)",
                            size_enum: -2, alignment_enum: 1, r: 255, g: 255, b: 255 }.label!
  end

#+end_src

*** Input Basics - Moving A Sprite - main.rb
#+begin_src ruby
  # ./samples/02_input_basics/01_moving_a_sprite/app/main.rb
  def tick args
    # create a player and set default values
    # for the player's x, y, w (width), and h (height)
    args.state.player.x ||= 100
    args.state.player.y ||= 100
    args.state.player.w ||=  50
    args.state.player.h ||=  50
  
    # render the player to the screen
    args.outputs.sprites << { x: args.state.player.x,
                              y: args.state.player.y,
                              w: args.state.player.w,
                              h: args.state.player.h,
                              path: 'sprites/square/green.png' }
  
    # move the player around using the keyboard
    if args.inputs.up
      args.state.player.y += 10
    elsif args.inputs.down
      args.state.player.y -= 10
    end
  
    if args.inputs.left
      args.state.player.x -= 10
    elsif args.inputs.right
      args.state.player.x += 10
    end
  end
  
  $gtk.reset

#+end_src

*** Input Basics - Mouse - main.rb
#+begin_src ruby
  # ./samples/02_input_basics/02_mouse/app/main.rb
  =begin
  
  APIs that haven't been encountered in a previous sample apps:
  
  - args.inputs.mouse.click: This property will be set if the mouse was clicked.
  - args.inputs.mouse.click.point.(x|y): The x and y location of the mouse.
  - args.inputs.mouse.click.point.created_at: The frame the mouse click occurred in.
  - args.inputs.mouse.click.point.created_at_elapsed: How many frames have passed
    since the click event.
  
  Reminder:
  
  - args.state.PROPERTY: The state property on args is a dynamic
    structure. You can define ANY property here with ANY type of
    arbitrary nesting. Properties defined on args.state will be retained
    across frames. If you attempt access a property that doesn't exist
    on args.state, it will simply return nil (no exception will be thrown).
  
  =end
  
  # This code demonstrates DragonRuby mouse input
  
  # To see if the a mouse click occurred
  # Use args.inputs.mouse.click
  # Which returns a boolean
  
  # To see where a mouse click occurred
  # Use args.inputs.mouse.click.point.x AND
  # args.inputs.mouse.click.point.y
  
  # To see which frame the click occurred
  # Use args.inputs.mouse.click.created_at
  
  # To see how many frames its been since the click occurred
  # Use args.inputs.mouse.click.created_at_elapsed
  
  # Saving the click in args.state can be quite useful
  
  def tick args
    tick_instructions args, "Sample app shows how mouse events are registered and how to measure elapsed time."
    x = 460
  
    args.outputs.labels << small_label(args, x, 11, "Mouse input: args.inputs.mouse")
  
    if args.inputs.mouse.click
      args.state.last_mouse_click = args.inputs.mouse.click
    end
  
    if args.state.last_mouse_click
      click = args.state.last_mouse_click
      args.outputs.labels << small_label(args, x, 12, "Mouse click happened at: #{click.created_at}")
      args.outputs.labels << small_label(args, x, 13, "Mouse clicked #{click.created_at_elapsed} ticks ago")
      args.outputs.labels << small_label(args, x, 14, "Mouse click location: #{click.point.x}, #{click.point.y}")
    else
      args.outputs.labels << small_label(args, x, 12, "Mouse click has not occurred yet.")
      args.outputs.labels << small_label(args, x, 13, "Please click mouse.")
    end
  end
  
  def small_label args, x, row, message
    # This method effectively combines the row_to_px and small_font methods
    # It changes the given row value to a DragonRuby pixel value
    # and adds the customization parameters
    { x: x, y: row_to_px(args, row), text: message, alignment_enum: -2 }
  end
  
  def row_to_px args, row_number
    args.grid.top.shift_down(5).shift_down(20 * row_number)
  end
  
  def tick_instructions args, text, y = 715
    return if args.state.key_event_occurred
    if args.inputs.mouse.click ||
       args.inputs.keyboard.directional_vector ||
       args.inputs.keyboard.key_down.enter ||
       args.inputs.keyboard.key_down.escape
      args.state.key_event_occurred = true
    end
  
    args.outputs.debug << { x: 0,   y: y - 50, w: 1280, h: 60 }.solid!
    args.outputs.debug << { x: 640, y: y, text: text, size_enum: 1, alignment_enum: 1, r: 255, g: 255, b: 255 }.label!
    args.outputs.debug << { x: 640, y: y - 25, text: "(click to dismiss instructions)", size_enum: -2, alignment_enum: 1, r: 255, g: 255, b: 255 }.label!
  end

#+end_src

*** Input Basics - Mouse Point To Rect - main.rb
#+begin_src ruby
  # ./samples/02_input_basics/03_mouse_point_to_rect/app/main.rb
  =begin
  
  APIs that haven't been encountered in a previous sample apps:
  
  - args.outputus.borders: An array. Values in this array will be rendered as
    unfilled rectangles on the screen.
  - ARRAY#inside_rect?: An array with at least two values is considered a point. An array
    with at least four values is considered a rect. The inside_rect? function returns true
    or false depending on if the point is inside the rect.
  
    ```
    # Point:  x: 100, y: 100
    # Rect:   x: 0, y: 0, w: 500, h: 500
    # Result: true
  
    [100, 100].inside_rect? [0, 0, 500, 500]
    ```
  
    ```
    # Point:  x: 100, y: 100
    # Rect:   x: 300, y: 300, w: 100, h: 100
    # Result: false
  
    [100, 100].inside_rect? [300, 300, 100, 100]
    ```
  
  - args.inputs.mouse.click.point.created_at: The frame the mouse click occurred in.
  - args.inputs.mouse.click.point.created_at_elapsed: How many frames have passed
    since the click event.
  
  =end
  
  # To determine whether a point is in a rect
  # Use point.inside_rect? rect
  
  # This is useful to determine if a click occurred in a rect
  
  def tick args
    tick_instructions args, "Sample app shows how to determing if a click happened inside a rectangle."
  
    x = 460
  
    args.outputs.labels << small_label(args, x, 15, "Click inside the blue box maybe ---->")
  
    box = { x: 785, y: 370, w: 50, h: 50, r: 0, g: 0, b: 170 }
    args.outputs.borders << box
  
    # Saves the most recent click into args.state
    # Unlike the other components of args,
    # args.state does not reset every tick.
    if args.inputs.mouse.click
      args.state.last_mouse_click = args.inputs.mouse.click
    end
  
    if args.state.last_mouse_click
      if args.state.last_mouse_click.point.inside_rect? box
        args.outputs.labels << small_label(args, x, 16, "Mouse click happened *inside* the box.")
      else
        args.outputs.labels << small_label(args, x, 16, "Mouse click happened *outside* the box.")
      end
    else
      args.outputs.labels << small_label(args, x, 16, "Mouse click has not occurred yet.")
    end
  end
  
  def small_label args, x, row, message
    { x: x, y: row_to_px(args, row), text: message, size_enum: -2 }
  end
  
  def row_to_px args, row_number
    args.grid.top.shift_down(5).shift_down(20 * row_number)
  end
  
  def tick_instructions args, text, y = 715
    return if args.state.key_event_occurred
    if args.inputs.mouse.click ||
       args.inputs.keyboard.directional_vector ||
       args.inputs.keyboard.key_down.enter ||
       args.inputs.keyboard.key_down.escape
      args.state.key_event_occurred = true
    end
  
    args.outputs.debug << { x: 0,   y: y - 50, w: 1280, h: 60 }.solid!
    args.outputs.debug << { x: 640, y: y, text: text, size_enum: 1, alignment_enum: 1, r: 255, g: 255, b: 255 }.label!
    args.outputs.debug << { x: 640, y: y - 25, text: "(click to dismiss instructions)", size_enum: -2, alignment_enum: 1, r: 255, g: 255, b: 255 }.label!
  end

#+end_src

*** Input Basics - Mouse Rect To Rect - main.rb
#+begin_src ruby
  # ./samples/02_input_basics/04_mouse_rect_to_rect/app/main.rb
  =begin
  
  APIs that haven't been encountered in a previous sample apps:
  
  - args.outputs.borders: An array. Values in this array will be rendered as
    unfilled rectangles on the screen.
  - ARRAY#intersect_rect?: An array with at least four values is
    considered a rect. The intersect_rect? function returns true
    or false depending on if the two rectangles intersect.
  
    ```
    # Rect One: x: 100, y: 100, w: 100, h: 100
    # Rect Two: x: 0, y: 0, w: 500, h: 500
    # Result:   true
  
    [100, 100, 100, 100].intersect_rect? [0, 0, 500, 500]
    ```
  
    ```
    # Rect One: x: 100, y: 100, w: 10, h: 10
    # Rect Two: x: 500, y: 500, w: 10, h: 10
    # Result:   false
  
    [100, 100, 10, 10].intersect_rect? [500, 500, 10, 10]
    ```
  
  =end
  
  # Similarly, whether rects intersect can be found through
  # rect1.intersect_rect? rect2
  
  def tick args
    tick_instructions args, "Sample app shows how to determine if two rectangles intersect."
    x = 460
  
    args.outputs.labels << small_label(args, x, 3, "Click anywhere on the screen")
    # red_box = [460, 250, 355, 90, 170, 0, 0]
    # args.outputs.borders << red_box
  
    # args.state.box_collision_one and args.state.box_collision_two
    # Are given values of a solid when they should be rendered
    # They are stored in game so that they do not get reset every tick
    if args.inputs.mouse.click
      if !args.state.box_collision_one
        args.state.box_collision_one = { x: args.inputs.mouse.click.point.x - 25,
                                         y: args.inputs.mouse.click.point.y - 25,
                                         w: 125, h: 125,
                                         r: 180, g: 0, b: 0, a: 180 }
      elsif !args.state.box_collision_two
        args.state.box_collision_two = { x: args.inputs.mouse.click.point.x - 25,
                                         y: args.inputs.mouse.click.point.y - 25,
                                         w: 125, h: 125,
                                         r: 0, g: 0, b: 180, a: 180 }
      else
        args.state.box_collision_one = nil
        args.state.box_collision_two = nil
      end
    end
  
    if args.state.box_collision_one
      args.outputs.solids << args.state.box_collision_one
    end
  
    if args.state.box_collision_two
      args.outputs.solids << args.state.box_collision_two
    end
  
    if args.state.box_collision_one && args.state.box_collision_two
      if args.state.box_collision_one.intersect_rect? args.state.box_collision_two
        args.outputs.labels << small_label(args, x, 4, 'The boxes intersect.')
      else
        args.outputs.labels << small_label(args, x, 4, 'The boxes do not intersect.')
      end
    else
      args.outputs.labels << small_label(args, x, 4, '--')
    end
  end
  
  def small_label args, x, row, message
    { x: x, y: row_to_px(args, row), text: message, size_enum: -2 }
  end
  
  def row_to_px args, row_number
    args.grid.top - 5 - (20 * row_number)
  end
  
  def tick_instructions args, text, y = 715
    return if args.state.key_event_occurred
    if args.inputs.mouse.click ||
       args.inputs.keyboard.directional_vector ||
       args.inputs.keyboard.key_down.enter ||
       args.inputs.keyboard.key_down.escape
      args.state.key_event_occurred = true
    end
  
    args.outputs.debug << [0, y - 50, 1280, 60].solid
    args.outputs.debug << [640, y, text, 1, 1, 255, 255, 255].label
    args.outputs.debug << [640, y - 25, "(click to dismiss instructions)" , -2, 1, 255, 255, 255].label
  end

#+end_src

*** Input Basics - Controller - main.rb
#+begin_src ruby
  # ./samples/02_input_basics/05_controller/app/main.rb
  =begin
  
   APIs listing that haven't been encountered in previous sample apps:
  
   - args.inputs.controller_one.key_held.KEY: Will check to see if a specific key
     is being held down on the controller.
     If there is more than one controller being used, they can be differentiated by
     using names like controller_one and controller_two.
  
     For a full listing of buttons, take a look at mygame/documentation/08-controllers.md.
  
   Reminder:
  
   - args.state.PROPERTY: The state property on args is a dynamic
     structure. You can define ANY property here with ANY type of
     arbitrary nesting. Properties defined on args.state will be retained
     across frames. If you attempt to access a property that doesn't exist
     on args.state, it will simply return nil (no exception will be thrown).
  
     In this sample app, args.state.BUTTONS is an array that stores the buttons of the controller.
     The parameters of a button are:
     1. the position (x, y)
     2. the input key held on the controller
     3. the text or name of the button
  
  =end
  
  # This sample app provides a visual demonstration of a standard controller, including
  # the placement and function of all buttons.
  
  class ControllerDemo
    attr_accessor :inputs, :state, :outputs
  
    # Calls the methods necessary for the app to run successfully.
    def tick
      process_inputs
      render
    end
  
    # Starts with an empty collection of buttons.
    # Adds buttons that are on the controller to the collection.
    def process_inputs
      state.buttons = []
  
      state.buttons << { x: 100,  y: 500, active: inputs.controller_one.key_held.l1, text: "L1"}
      state.buttons << { x: 100,  y: 600, active: inputs.controller_one.key_held.l2, text: "L2"}
      state.buttons << { x: 1100, y: 500, active: inputs.controller_one.key_held.r1, text: "R1"}
      state.buttons << { x: 1100, y: 600, active: inputs.controller_one.key_held.r2, text: "R2"}
      state.buttons << { x: 540,  y: 450, active: inputs.controller_one.key_held.select, text: "Select"}
      state.buttons << { x: 660,  y: 450, active: inputs.controller_one.key_held.start, text: "Start"}
      state.buttons << { x: 200,  y: 300, active: inputs.controller_one.key_held.left, text: "Left"}
      state.buttons << { x: 300,  y: 400, active: inputs.controller_one.key_held.up, text: "Up"}
      state.buttons << { x: 400,  y: 300, active: inputs.controller_one.key_held.right, text: "Right"}
      state.buttons << { x: 300,  y: 200, active: inputs.controller_one.key_held.down, text: "Down"}
      state.buttons << { x: 800,  y: 300, active: inputs.controller_one.key_held.x, text: "X"}
      state.buttons << { x: 900,  y: 400, active: inputs.controller_one.key_held.y, text: "Y"}
      state.buttons << { x: 1000, y: 300, active: inputs.controller_one.key_held.a, text: "A"}
      state.buttons << { x: 900,  y: 200, active: inputs.controller_one.key_held.b, text: "B"}
      state.buttons << { x: 450 + inputs.controller_one.left_analog_x_perc * 100,
                         y: 100 + inputs.controller_one.left_analog_y_perc * 100,
                         active: inputs.controller_one.key_held.l3,
                         text: "L3" }
      state.buttons << { x: 750 + inputs.controller_one.right_analog_x_perc * 100,
                         y: 100 + inputs.controller_one.right_analog_y_perc * 100,
                         active: inputs.controller_one.key_held.r3,
                         text: "R3" }
    end
  
    # Gives each button a square shape.
    # If the button is being pressed or held (which means it is considered active),
    # the square is filled in. Otherwise, the button simply has a border.
    def render
      state.buttons.each do |b|
        rect = { x: b.x, y: b.y, w: 75, h: 75 }
  
        if b.active # if button is pressed
          outputs.solids << rect # rect is output as solid (filled in)
        else
          outputs.borders << rect # otherwise, output as border
        end
  
        # Outputs the text of each button using labels.
        outputs.labels << { x: b.x, y: b.y + 95, text: b.text } # add 95 to place label above button
      end
  
      outputs.labels << { x:  10, y: 60, text: "Left Analog x: #{inputs.controller_one.left_analog_x_raw} (#{inputs.controller_one.left_analog_x_perc * 100}%)" }
      outputs.labels << { x:  10, y: 30, text: "Left Analog y: #{inputs.controller_one.left_analog_y_raw} (#{inputs.controller_one.left_analog_y_perc * 100}%)" }
      outputs.labels << { x: 900, y: 60, text: "Right Analog x: #{inputs.controller_one.right_analog_x_raw} (#{inputs.controller_one.right_analog_x_perc * 100}%)" }
      outputs.labels << { x: 900, y: 30, text: "Right Analog y: #{inputs.controller_one.right_analog_y_raw} (#{inputs.controller_one.right_analog_y_perc * 100}%)" }
    end
  end
  
  $controller_demo = ControllerDemo.new
  
  def tick args
    tick_instructions args, "Sample app shows how controller input is handled. You'll need to connect a USB controller."
    $controller_demo.inputs = args.inputs
    $controller_demo.state = args.state
    $controller_demo.outputs = args.outputs
    $controller_demo.tick
  end
  
  # Resets the app.
  def r
    $gtk.reset
  end
  
  def tick_instructions args, text, y = 715
    return if args.state.key_event_occurred
    if args.inputs.mouse.click ||
       args.inputs.keyboard.directional_vector ||
       args.inputs.keyboard.key_down.enter ||
       args.inputs.keyboard.key_down.escape
      args.state.key_event_occurred = true
    end
  
    args.outputs.debug << [0, y - 50, 1280, 60].solid
    args.outputs.debug << [640, y, text, 1, 1, 255, 255, 255].label
    args.outputs.debug << [640, y - 25, "(click to dismiss instructions)" , -2, 1, 255, 255, 255].label
  end

#+end_src

*** Input Basics - Touch - main.rb
#+begin_src ruby
  # ./samples/02_input_basics/06_touch/app/main.rb
  def tick args
    args.outputs.background_color = [ 0, 0, 0 ]
    args.outputs.primitives << [640, 700, "Touch your screen.", 5, 1, 255, 255, 255].label
  
    # If you don't want to get fancy, you can just look for finger_one
    #  (and _two, if you like), which are assigned in the order new touches hit
    #  the screen. If not nil, they are touching right now, and are just
    #  references to specific items in the args.input.touch hash.
    # If finger_one lifts off, it will become nil, but finger_two, if it was
    #  touching, remains until it also lifts off. When all fingers lift off, the
    #  the next new touch will be finger_one again, but until then, new touches
    #  don't fill in earlier slots.
    if !args.inputs.finger_one.nil?
      args.outputs.primitives << { x: 640, y: 650, text: "Finger #1 is touching at (#{args.inputs.finger_one.x}, #{args.inputs.finger_one.y}).",
                                   size_enum: 5, alignment_enum: 1, r: 255, g: 255, b: 255 }.label!
    end
    if !args.inputs.finger_two.nil?
      args.outputs.primitives << { x: 640, y: 600, text: "Finger #2 is touching at (#{args.inputs.finger_two.x}, #{args.inputs.finger_two.y}).",
                                   size_enum: 5, alignment_enum: 1, r: 255, g: 255, b: 255 }.label!
    end
  
    # Here's the more flexible interface: this will report as many simultaneous
    #  touches as the system can handle, but it's a little more effort to track
    #  them. Each item in the args.input.touch hash has a unique key (an
    #  incrementing integer) that exists until the finger lifts off. You can
    #  tell which order the touches happened globally by the key value, or
    #  by the touch[id].touch_order field, which resets to zero each time all
    #  touches have lifted.
  
    args.state.colors ||= [
      0xFF0000, 0x00FF00, 0x1010FF, 0xFFFF00, 0xFF00FF, 0x00FFFF, 0xFFFFFF
    ]
  
    size = 100
    args.inputs.touch.each { |k,v|
      color = args.state.colors[v.touch_order % 7]
      r = (color & 0xFF0000) >> 16
      g = (color & 0x00FF00) >> 8
      b = (color & 0x0000FF)
      args.outputs.primitives << { x: v.x - (size / 2), y: v.y + (size / 2), w: size, h: size, r: r, g: g, b: b, a: 255 }.solid!
      args.outputs.primitives << { x: v.x, y: v.y + size, text: k.to_s, alignment_enum: 1 }.label!
    }
  end

#+end_src

*** Rendering Sprites - Animation Using Separate Pngs - main.rb
#+begin_src ruby
  # ./samples/03_rendering_sprites/01_animation_using_separate_pngs/app/main.rb
  =begin
  
   Reminders:
  
   - String interpolation: Uses #{} syntax; everything between the #{ and the } is evaluated
     as Ruby code, and the placeholder is replaced with its corresponding value or result.
  
     In this sample app, we're using string interpolation to iterate through images in the
     sprites folder using their image path names.
  
   - args.outputs.sprites: An array. Values in this array generate sprites on the screen.
     The parameters are [X, Y, WIDTH, HEIGHT, IMAGE PATH]
     For more information about sprites, go to mygame/documentation/05-sprites.md.
  
   - args.outputs.labels: An array. Values in the array generate labels on the screen.
     The parameters are [X, Y, TEXT, SIZE, ALIGNMENT, RED, GREEN, BLUE, ALPHA, FONT STYLE]
     For more information about labels, go to mygame/documentation/02-labels.md.
  
   - args.inputs.keyboard.key_down.KEY: Determines if a key is in the down state, or pressed.
     Stores the frame that key was pressed on.
     For more information about the keyboard, go to mygame/documentation/06-keyboard.md.
  
  =end
  
  # This sample app demonstrates how sprite animations work.
  # There are two sprites that animate forever and one sprite
  # that *only* animates when you press the "f" key on the keyboard.
  
  # This is the entry point to your game. The `tick` method
  # executes at 60 frames per second. There are two methods
  # in this tick "entry point": `looping_animation`, and the
  # second method is `one_time_animation`.
  def tick args
    # uncomment the line below to see animation play out in slow motion
    # args.gtk.slowmo! 6
    looping_animation args
    one_time_animation args
  end
  
  # This function shows how to animate a sprite that loops forever.
  def looping_animation args
    # Here we define a few local variables that will be sent
    # into the magic function that gives us the correct sprite image
    # over time. There are four things we need in order to figure
    # out which sprite to show.
  
    # 1. When to start the animation.
    start_looping_at = 0
  
    # 2. The number of pngs that represent the full animation.
    number_of_sprites = 6
  
    # 3. How long to show each png.
    number_of_frames_to_show_each_sprite = 4
  
    # 4. Whether the animation should loop once, or forever.
    does_sprite_loop = true
  
    # With the variables defined above, we can get a number
    # which represents the sprite to show by calling the `frame_index` function.
    # In this case the number will be between 0, and 5 (you can see the sprites
    # in the ./sprites directory).
    sprite_index = start_looping_at.frame_index number_of_sprites,
                                                number_of_frames_to_show_each_sprite,
                                                does_sprite_loop
  
    # Now that we have `sprite_index, we can present the correct file.
    args.outputs.sprites << { x: 100, y: 100, w: 100, h: 100, path: "sprites/dragon_fly_#{sprite_index}.png" }
  
    # Try changing the numbers below to see how the animation changes:
    args.outputs.sprites << { x: 100, y: 200, w: 100, h: 100, path: "sprites/dragon_fly_#{0.frame_index 6, 4, true}.png" }
  end
  
  # This function shows how to animate a sprite that executes
  # only once when the "f" key is pressed.
  def one_time_animation args
    # This is just a label the shows instructions within the game.
    args.outputs.labels <<  { x: 220, y: 350, text: "(press f to animate)" }
  
    # If "f" is pressed on the keyboard...
    if args.inputs.keyboard.key_down.f
      # Print the frame that "f" was pressed on.
      puts "Hello from main.rb! The \"f\" key was in the down state on frame: #{args.state.tick_count}"
  
      # And MOST IMPORTANTLY set the point it time to start the animation,
      # equal to "now" which is represented as args.state.tick_count.
  
      # Also IMPORTANT, you'll notice that the value of when to start looping
      # is stored in `args.state`. This construct's values are retained across
      # executions of the `tick` method.
      args.state.start_looping_at = args.state.tick_count
    end
  
    # These are the same local variables that were defined
    # for the `looping_animation` function.
    number_of_sprites = 6
    number_of_frames_to_show_each_sprite = 4
  
    # Except this sprite does not loop again. If the animation time has passed,
    # then the frame_index function returns nil.
    does_sprite_loop = false
  
    sprite_index = args.state
                       .start_looping_at
                       .frame_index number_of_sprites,
                                    number_of_frames_to_show_each_sprite,
                                    does_sprite_loop
  
    # This line sets the frame index to zero, if
    # the animation duration has passed (frame_index returned nil).
  
    # Remeber: we are not looping forever here.
    sprite_index ||= 0
  
    # Present the sprite.
    args.outputs.sprites << { x: 100, y: 300, w: 100, h: 100, path: "sprites/dragon_fly_#{sprite_index}.png" }
  
    tick_instructions args, "Sample app shows how to use Numeric#frame_index and string interpolation to animate a sprite over time."
  end
  
  def tick_instructions args, text, y = 715
    return if args.state.key_event_occurred
    if args.inputs.mouse.click ||
       args.inputs.keyboard.directional_vector ||
       args.inputs.keyboard.key_down.enter ||
       args.inputs.keyboard.key_down.escape
      args.state.key_event_occurred = true
    end
  
    args.outputs.debug << [0, y - 50, 1280, 60].solid
    args.outputs.debug << [640, y, text, 1, 1, 255, 255, 255].label
    args.outputs.debug << [640, y - 25, "(click to dismiss instructions)" , -2, 1, 255, 255, 255].label
  end

#+end_src

*** Rendering Sprites - Animation Using Sprite Sheet - main.rb
#+begin_src ruby
  # ./samples/03_rendering_sprites/02_animation_using_sprite_sheet/app/main.rb
  def tick args
    args.state.player.x ||= 100
    args.state.player.y ||= 100
    args.state.player.w ||= 64
    args.state.player.h ||= 64
    args.state.player.direction ||= 1
  
    args.state.player.is_moving = false
  
    # get the keyboard input and set player properties
    if args.inputs.keyboard.right
      args.state.player.x += 3
      args.state.player.direction = 1
      args.state.player.started_running_at ||= args.state.tick_count
    elsif args.inputs.keyboard.left
      args.state.player.x -= 3
      args.state.player.direction = -1
      args.state.player.started_running_at ||= args.state.tick_count
    end
  
    if args.inputs.keyboard.up
      args.state.player.y += 1
      args.state.player.started_running_at ||= args.state.tick_count
    elsif args.inputs.keyboard.down
      args.state.player.y -= 1
      args.state.player.started_running_at ||= args.state.tick_count
    end
  
    # if no arrow keys are being pressed, set the player as not moving
    if !args.inputs.keyboard.directional_vector
      args.state.player.started_running_at = nil
    end
  
    # wrap player around the stage
    if args.state.player.x > 1280
      args.state.player.x = -64
      args.state.player.started_running_at ||= args.state.tick_count
    elsif args.state.player.x < -64
      args.state.player.x = 1280
      args.state.player.started_running_at ||= args.state.tick_count
    end
  
    if args.state.player.y > 720
      args.state.player.y = -64
      args.state.player.started_running_at ||= args.state.tick_count
    elsif args.state.player.y < -64
      args.state.player.y = 720
      args.state.player.started_running_at ||= args.state.tick_count
    end
  
    # render player as standing or running
    if args.state.player.started_running_at
      args.outputs.sprites << running_sprite(args)
    else
      args.outputs.sprites << standing_sprite(args)
    end
    args.outputs.labels << [30, 700, "Use arrow keys to move around."]
  end
  
  def standing_sprite args
    {
      x: args.state.player.x,
      y: args.state.player.y,
      w: args.state.player.w,
      h: args.state.player.h,
      path: "sprites/horizontal-stand.png",
      flip_horizontally: args.state.player.direction > 0
    }
  end
  
  def running_sprite args
    if !args.state.player.started_running_at
      tile_index = 0
    else
      how_many_frames_in_sprite_sheet = 6
      how_many_ticks_to_hold_each_frame = 3
      should_the_index_repeat = true
      tile_index = args.state
                       .player
                       .started_running_at
                       .frame_index(how_many_frames_in_sprite_sheet,
                                    how_many_ticks_to_hold_each_frame,
                                    should_the_index_repeat)
    end
  
    {
      x: args.state.player.x,
      y: args.state.player.y,
      w: args.state.player.w,
      h: args.state.player.h,
      path: 'sprites/horizontal-run.png',
      tile_x: 0 + (tile_index * args.state.player.w),
      tile_y: 0,
      tile_w: args.state.player.w,
      tile_h: args.state.player.h,
      flip_horizontally: args.state.player.direction > 0,
    }
  end

#+end_src

*** Rendering Sprites - Animation States - main.rb
#+begin_src ruby
  # ./samples/03_rendering_sprites/03_animation_states/app/main.rb
  class Game
    attr_gtk
  
    def defaults
      state.show_debug_layer  = true if state.tick_count == 0
      player.tile_size        = 64
      player.speed            = 3
      player.slash_frames     = 15
      player.x              ||= 50
      player.y              ||= 400
      player.dir_x          ||=  1
      player.dir_y          ||= -1
      player.is_moving      ||= false
      state.watch_list      ||= {}
      state.enemies         ||= []
    end
  
    def add_enemy
      state.enemies << { x: 1200 * rand, y: 600 * rand, w: 64, h: 64 }
    end
  
    def sprite_horizontal_run
      tile_index = 0.frame_index(6, 3, true)
      tile_index = 0 if !player.is_moving
  
      {
        x: player.x,
        y: player.y,
        w: player.tile_size,
        h: player.tile_size,
        path: 'sprites/horizontal-run.png',
        tile_x: 0 + (tile_index * player.tile_size),
        tile_y: 0,
        tile_w: player.tile_size,
        tile_h: player.tile_size,
        flip_horizontally: player.dir_x > 0,
        # a: 40
      }
    end
  
    def sprite_horizontal_stand
      {
        x: player.x,
        y: player.y,
        w: player.tile_size,
        h: player.tile_size,
        path: 'sprites/horizontal-stand.png',
        flip_horizontally: player.dir_x > 0,
        # a: 40
      }
    end
  
    def sprite_horizontal_slash
      tile_index   = player.slash_at.frame_index(5, player.slash_frames.idiv(5), false) || 0
  
      {
        x: player.x - 41.25,
        y: player.y - 41.25,
        w: 165,
        h: 165,
        path: 'sprites/horizontal-slash.png',
        tile_x: 0 + (tile_index * 128),
        tile_y: 0,
        tile_w: 128,
        tile_h: 128,
        flip_horizontally: player.dir_x > 0
      }
    end
  
    def render_player
      if player.slash_at
        outputs.sprites << sprite_horizontal_slash
      elsif player.is_moving
        outputs.sprites << sprite_horizontal_run
      else
        outputs.sprites << sprite_horizontal_stand
      end
    end
  
    def render_enemies
      outputs.borders << state.enemies
    end
  
    def render_debug_layer
      return if !state.show_debug_layer
      outputs.labels << state.watch_list.map.with_index do |(k, v), i|
         [30, 710 - i * 28, "#{k}: #{v || "(nil)"}"]
      end
  
      outputs.borders << player.slash_collision_rect
    end
  
    def slash_initiate?
      # buffalo usb controller has a button and b button swapped lol
      inputs.controller_one.key_down.a || inputs.keyboard.key_down.j
    end
  
    def input
      # player movement
      if slash_complete? && (vector = inputs.directional_vector)
        player.x += vector.x * player.speed
        player.y += vector.y * player.speed
      end
      player.slash_at = slash_initiate? if slash_initiate?
    end
  
    def calc_movement
      # movement
      if vector = inputs.directional_vector
        state.debug_label = vector
        player.dir_x = vector.x
        player.dir_y = vector.y
        player.is_moving = true
      else
        state.debug_label = vector
        player.is_moving = false
      end
    end
  
    def calc_slash
      # re-calc the location of the swords collision box
      if player.dir_x.positive?
        player.slash_collision_rect = [player.x + player.tile_size,
                                       player.y + player.tile_size.half - 10,
                                       40, 20]
      else
        player.slash_collision_rect = [player.x - 32 - 8,
                                       player.y + player.tile_size.half - 10,
                                       40, 20]
      end
  
      # recalc sword's slash state
      player.slash_at = nil if slash_complete?
  
      # determine collision if the sword is at it's point of damaging
      return unless slash_can_damage?
  
      state.enemies.reject! { |e| e.intersect_rect? player.slash_collision_rect }
    end
  
    def slash_complete?
      !player.slash_at || player.slash_at.elapsed?(player.slash_frames)
    end
  
    def slash_can_damage?
      # damage occurs half way into the slash animation
      return false if slash_complete?
      return false if (player.slash_at + player.slash_frames.idiv(2)) != state.tick_count
      return true
    end
  
    def calc
      # generate an enemy if there aren't any on the screen
      add_enemy if state.enemies.length == 0
      calc_movement
      calc_slash
    end
  
    # source is at http://github.com/amirrajan/dragonruby-link-to-the-past
    def tick
      defaults
      render_enemies
      render_player
      outputs.labels << [30, 30, "Gamepad: D-Pad to move. B button to attack."]
      outputs.labels << [30, 52, "Keyboard: WASD/Arrow keys to move. J to attack."]
      render_debug_layer
      input
      calc
    end
  
    def player
      state.player
    end
  end
  
  $game = Game.new
  
  def tick args
    $game.args = args
    $game.tick
  end
  
  $gtk.reset

#+end_src

*** Rendering Sprites - Color And Rotation - main.rb
#+begin_src ruby
  # ./samples/03_rendering_sprites/04_color_and_rotation/app/main.rb
  =begin
   APIs listing that haven't been encountered in previous sample apps:
  
   - merge: Returns a hash containing the contents of two original hashes.
     Merge does not allow duplicate keys, so the value of a repeated key
     will be overwritten.
  
     For example, if we had two hashes
     h1 = { "a" => 1, "b" => 2}
     h2 = { "b" => 3, "c" => 3}
     and we called the command
     h1.merge(h2)
     the result would the following hash
     { "a" => 1, "b" => 3, "c" => 3}.
  
   Reminders:
  
   - Hashes: Collection of unique keys and their corresponding values. The value can be found
     using their keys.
     In this sample app, we're using a hash to create a sprite.
  
   - args.outputs.sprites: An array. The values generate a sprite.
     The parameters are [X, Y, WIDTH, HEIGHT, PATH, ANGLE, ALPHA, RED, GREEN, BLUE]
     Before continuing with this sample app, it is HIGHLY recommended that you look
     at mygame/documentation/05-sprites.md.
  
   - args.inputs.keyboard.key_held.KEY: Determines if a key is being pressed.
     For more information about the keyboard, go to mygame/documentation/06-keyboard.md.
  
   - args.inputs.controller_one: Takes input from the controller based on what key is pressed.
     For more information about the controller, go to mygame/documentation/08-controllers.md.
  
   - num1.lesser(num2): Finds the lower value of the given options.
  
  =end
  
  # This sample app shows a car moving across the screen. It loops back around if it exceeds the dimensions of the screen,
  # and also can be moved in different directions through keyboard input from the user.
  
  # Calls the methods necessary for the game to run successfully.
  def tick args
    default args
    render args.grid, args.outputs, args.state
    calc args.state
    process_inputs args
  end
  
  # Sets default values for the car sprite
  # Initialization ||= only happens in the first frame
  def default args
    args.state.sprite.width    = 19
    args.state.sprite.height   = 10
    args.state.sprite.scale    = 4
    args.state.max_speed       = 5
    args.state.x             ||= 100
    args.state.y             ||= 100
    args.state.speed         ||= 1
    args.state.angle         ||= 0
  end
  
  # Outputs sprite onto screen
  def render grid, outputs, state
    outputs.solids  <<  [grid.rect, 70, 70, 70] # outputs gray background
    outputs.sprites <<  [destination_rect(state), # sets first four parameters of car sprite
    'sprites/86.png', # image path of car
    state.angle,
    opacity, # transparency
    saturation,
    source_rect(state), # sprite sub division/tile (tile x, y, w, h)
    false, false,  # don't flip sprites
    rotation_anchor]
  
    # also look at the create_sprite helper method
    #
    # For example:
    #
    # dest   = destination_rect(state)
    # source = source_rect(state),
    # outputs.sprites << create_sprite(
    #   'sprites/86.png',
    #   x: dest.x,
    #   y: dest.y,
    #   w: dest.w,
    #   h: dest.h,
    #   angle: state.angle,
    #   source_x: source.x,
    #   source_y: source.y,
    #   source_w: source.w,
    #   source_h: source.h,
    #   flip_h: false,
    #   flip_v: false,
    #   rotation_anchor_x: 0.7,
    #   rotation_anchor_y: 0.5
    # )
  end
  
  # Creates sprite by setting values inside of a hash
  def create_sprite path, options = {}
    options = {
  
      # dest x, y, w, h
      x: 0,
      y: 0,
      w: 100,
      h: 100,
  
      # angle, rotation
      angle: 0,
      rotation_anchor_x: 0.5,
      rotation_anchor_y: 0.5,
  
      # color saturation (red, green, blue), transparency
      r: 255,
      g: 255,
      b: 255,
      a: 255,
  
      # source x, y, width, height
      source_x: 0,
      source_y: 0,
      source_w: -1,
      source_h: -1,
  
      # flip horiztonally, flip vertically
      flip_h: false,
      flip_v: false,
  
    }.merge options
  
    [
      options[:x], options[:y], options[:w], options[:h], # dest rect keys
      path,
      options[:angle], options[:a], options[:r], options[:g], options[:b], # angle, color, alpha
      options[:source_x], options[:source_y], options[:source_w], options[:source_h], # source rect keys
      options[:flip_h], options[:flip_v], # flip
      options[:rotation_anchor_x], options[:rotation_anchor_y], # rotation anchor
    ] # hash keys contain corresponding values
  end
  
  # Calls the calc_pos and calc_wrap methods.
  def calc state
    calc_pos state
    calc_wrap state
  end
  
  # Changes sprite's position on screen
  # Vectors have magnitude and direction, so the incremented x and y values give the car direction
  def calc_pos state
    state.x     += state.angle.vector_x * state.speed # increments x by product of angle's x vector and speed
    state.y     += state.angle.vector_y * state.speed # increments y by product of angle's y vector and speed
    state.speed *= 1.1 # scales speed up
    state.speed  = state.speed.lesser(state.max_speed) # speed is either current speed or max speed, whichever has a lesser value (ensures that the car doesn't go too fast or exceed the max speed)
  end
  
  # The screen's dimensions are 1280x720. If the car goes out of scope,
  # it loops back around on the screen.
  def calc_wrap state
  
    # car returns to left side of screen if it disappears on right side of screen
    # sprite.width refers to tile's size, which is multipled by scale (4) to make it bigger
    state.x = -state.sprite.width * state.sprite.scale if state.x - 20 > 1280
  
    # car wraps around to right side of screen if it disappears on the left side
    state.x = 1280 if state.x + state.sprite.width * state.sprite.scale + 20 < 0
  
    # car wraps around to bottom of screen if it disappears at the top of the screen
    # if you subtract 520 pixels instead of 20 pixels, the car takes longer to reappear (try it!)
    state.y = 0    if state.y - 20 > 720 # if 20 pixels less than car's y position is greater than vertical scope
  
    # car wraps around to top of screen if it disappears at the bottom of the screen
    state.y = 720  if state.y + state.sprite.height * state.sprite.scale + 20 < 0
  end
  
  # Changes angle of sprite based on user input from keyboard or controller
  def process_inputs args
  
    # NOTE: increasing the angle doesn't mean that the car will continue to go
    # in a specific direction. The angle is increasing, which means that if the
    # left key was kept in the "down" state, the change in the angle would cause
    # the car to go in a counter-clockwise direction and form a circle (360 degrees)
    if args.inputs.keyboard.key_held.left # if left key is pressed
      args.state.angle += 2 # car's angle is incremented by 2
  
    # The same applies to decreasing the angle. If the right key was kept in the
    # "down" state, the decreasing angle would cause the car to go in a clockwise
    # direction and form a circle (360 degrees)
    elsif args.inputs.keyboard.key_held.right # if right key is pressed
      args.state.angle -= 2 # car's angle is decremented by 2
  
    # Input from a controller can also change the angle of the car
    elsif args.inputs.controller_one.left_analog_x_perc != 0
      args.state.angle += 2 * args.inputs.controller_one.left_analog_x_perc * -1
    end
  end
  
  # A sprite's center of rotation can be altered
  # Increasing either of these numbers would dramatically increase the
  # car's drift when it turns!
  def rotation_anchor
    [0.7, 0.5]
  end
  
  # Sets opacity value of sprite to 255 so that it is not transparent at all
  # Change it to 0 and you won't be able to see the car sprite on the screen
  def opacity
    255
  end
  
  # Sets the color of the sprite to white.
  def saturation
    [255, 255, 255]
  end
  
  # Sets definition of destination_rect (used to define the car sprite)
  def destination_rect state
    [state.x, state.y,
    state.sprite.width  * state.sprite.scale, # multiplies by 4 to set size
    state.sprite.height * state.sprite.scale]
  end
  
  # Portion of a sprite (a tile)
  # Sub division of sprite is denoted as a rectangle directly related to original size of .png
  # Tile is located at bottom left corner within a 19x10 pixel rectangle (based on sprite.width, sprite.height)
  def source_rect state
    [0, 0, state.sprite.width, state.sprite.height]
  end

#+end_src

*** Physics And Collisions - Simple - main.rb
#+begin_src ruby
  # ./samples/04_physics_and_collisions/01_simple/app/main.rb
  =begin
  
   Reminders:
   - ARRAY#intersect_rect?: Returns true or false depending on if the two rectangles intersect.
  
   - args.outputs.solids: An array. The values generate a solid.
     The parameters are [X, Y, WIDTH, HEIGHT, RED, GREEN, BLUE]
  
  =end
  
  # This sample app shows collisions between two boxes.
  
  # Runs methods needed for game to run properly.
  def tick args
    tick_instructions args, "Sample app shows how to move a square over time and determine collision."
    defaults args
    render args
    calc args
  end
  
  # Sets default values.
  def defaults args
    # These values represent the moving box.
    args.state.moving_box_speed   = 10
    args.state.moving_box_size    = 100
    args.state.moving_box_dx    ||=  1
    args.state.moving_box_dy    ||=  1
    args.state.moving_box       ||= [0, 0, args.state.moving_box_size, args.state.moving_box_size] # moving_box_size is set as the width and height
  
    # These values represent the center box.
    args.state.center_box ||= [540, 260, 200, 200, 180]
    args.state.center_box_collision ||= false # initially no collision
  end
  
  def render args
    # If the game state denotes that a collision has occured,
    # render a solid square, otherwise render a border instead.
    if args.state.center_box_collision
      args.outputs.solids << args.state.center_box
    else
      args.outputs.borders << args.state.center_box
    end
  
    # Then render the moving box.
    args.outputs.solids << args.state.moving_box
  end
  
  # Generally in a pipeline for a game engine, you have rendering,
  # game simulation (calculation), and input processing.
  # This fuction represents the game simulation.
  def calc args
    position_moving_box args
    determine_collision_center_box args
  end
  
  # Changes the position of the moving box on the screen by multiplying the change in x (dx) and change in y (dy) by the speed,
  # and adding it to the current position.
  # dx and dy are positive if the box is moving right and up, respectively
  # dx and dy are negative if the box is moving left and down, respectively
  def position_moving_box args
    args.state.moving_box.x += args.state.moving_box_dx * args.state.moving_box_speed
    args.state.moving_box.y += args.state.moving_box_dy * args.state.moving_box_speed
  
    # 1280x720 are the virtual pixels you work with (essentially 720p).
    screen_width  = 1280
    screen_height = 720
  
    # Position of the box is denoted by the bottom left hand corner, in
    # that case, we have to subtract the width of the box so that it stays
    # in the scene (you can try deleting the subtraction to see how it
    # impacts the box's movement).
    if args.state.moving_box.x > screen_width - args.state.moving_box_size
      args.state.moving_box_dx = -1 # moves left
    elsif args.state.moving_box.x < 0
      args.state.moving_box_dx =  1 # moves right
    end
  
    # Here, we're making sure the moving box remains within the vertical scope of the screen
    if args.state.moving_box.y > screen_height - args.state.moving_box_size # if the box moves too high
      args.state.moving_box_dy = -1 # moves down
    elsif args.state.moving_box.y < 0 # if the box moves too low
      args.state.moving_box_dy =  1 # moves up
    end
  end
  
  def determine_collision_center_box args
    # Collision is handled by the engine. You simply have to call the
    # `intersect_rect?` function.
    if args.state.moving_box.intersect_rect? args.state.center_box # if the two boxes intersect
      args.state.center_box_collision = true # then a collision happened
    else
      args.state.center_box_collision = false # otherwise, no collision happened
    end
  end
  
  def tick_instructions args, text, y = 715
    return if args.state.key_event_occurred
    if args.inputs.mouse.click ||
       args.inputs.keyboard.directional_vector ||
       args.inputs.keyboard.key_down.enter ||
       args.inputs.keyboard.key_down.escape
      args.state.key_event_occurred = true
    end
  
    args.outputs.debug << [0, y - 50, 1280, 60].solid
    args.outputs.debug << [640, y, text, 1, 1, 255, 255, 255].label
    args.outputs.debug << [640, y - 25, "(click to dismiss instructions)" , -2, 1, 255, 255, 255].label
  end

#+end_src

*** Physics And Collisions - Moving Objects - main.rb
#+begin_src ruby
  # ./samples/04_physics_and_collisions/02_moving_objects/app/main.rb
  =begin
  
   APIs listing that haven't been encountered in previous sample apps:
  
   - Hashes: Collection of unique keys and their corresponding values. The value can be found
     using their keys.
  
     For example, if we have a "numbers" hash that stores numbers in English as the
     key and numbers in Spanish as the value, we'd have a hash that looks like this...
     numbers = { "one" => "uno", "two" => "dos", "three" => "tres" }
     and on it goes.
  
     Now if we wanted to find the corresponding value of the "one" key, we could say
     puts numbers["one"]
     which would print "uno" to the console.
  
   - num1.greater(num2): Returns the greater value.
     For example, if we have the command
     puts 4.greater(3)
     the number 4 would be printed to the console since it has a greater value than 3.
     Similar to lesser, which returns the lesser value.
  
   - num1.lesser(num2): Finds the lower value of the given options.
     For example, in the statement
     a = 4.lesser(3)
     3 has a lower value than 4, which means that the value of a would be set to 3,
     but if the statement had been
     a = 4.lesser(5)
     4 has a lower value than 5, which means that the value of a would be set to 4.
  
   - reject: Removes elements from a collection if they meet certain requirements.
     For example, you can derive an array of odd numbers from an original array of
     numbers 1 through 10 by rejecting all elements that are even (or divisible by 2).
  
   - find_all: Finds all values that satisfy specific requirements.
     For example, you can find all elements of a collection that are divisible by 2
     or find all objects that have intersected with another object.
  
   - abs: Returns the absolute value.
     For example, the command
     (-30).abs
     would return 30 as a result.
  
   - map: Ruby method used to transform data; used in arrays, hashes, and collections.
     Can be used to perform an action on every element of a collection, such as multiplying
     each element by 2 or declaring every element as a new entity.
  
   Reminders:
  
   - args.inputs.keyboard.KEY: Determines if a key has been pressed.
     For more information about the keyboard, take a look at mygame/documentation/06-keyboard.md.
  
   - ARRAY#intersect_rect?: Returns true or false depending on if the two rectangles intersect.
  
   - args.outputs.solids: An array. The values generate a solid.
     The parameters are [X, Y, WIDTH, HEIGHT, RED, GREEN, BLUE]
     For more information about solids, go to mygame/documentation/03-solids-and-borders.md.
  
  =end
  
  # Calls methods needed for game to run properly
  def tick args
    tick_instructions args, "Use LEFT and RIGHT arrow keys to move and SPACE to jump."
    defaults args
    render args
    calc args
    input args
  end
  
  # sets default values and creates empty collections
  # initialization only happens in the first frame
  def defaults args
    fiddle args
    args.state.enemy.hammers ||= []
    args.state.enemy.hammer_queue ||= []
    args.state.tick_count = args.state.tick_count
    args.state.bridge_top = 128
    args.state.player.x  ||= 0                        # initializes player's properties
    args.state.player.y  ||= args.state.bridge_top
    args.state.player.w  ||= 64
    args.state.player.h  ||= 64
    args.state.player.dy ||= 0
    args.state.player.dx ||= 0
    args.state.enemy.x   ||= 800                      # initializes enemy's properties
    args.state.enemy.y   ||= 0
    args.state.enemy.w   ||= 128
    args.state.enemy.h   ||= 128
    args.state.enemy.dy  ||= 0
    args.state.enemy.dx  ||= 0
    args.state.game_over_at ||= 0
  end
  
  # sets enemy, player, hammer values
  def fiddle args
    args.state.gravity                     = -0.3
    args.state.enemy_jump_power            = 10       # sets enemy values
    args.state.enemy_jump_interval         = 60
    args.state.hammer_throw_interval       = 40       # sets hammer values
    args.state.hammer_launch_power_default = 5
    args.state.hammer_launch_power_near    = 2
    args.state.hammer_launch_power_far     = 7
    args.state.hammer_upward_launch_power  = 15
    args.state.max_hammers_per_volley      = 10
    args.state.gap_between_hammers         = 10
    args.state.player_jump_power           = 10       # sets player values
    args.state.player_jump_power_duration  = 10
    args.state.player_max_run_speed        = 10
    args.state.player_speed_slowdown_rate  = 0.9
    args.state.player_acceleration         = 1
    args.state.hammer_size                 = 32
  end
  
  # outputs objects onto the screen
  def render args
    args.outputs.solids << 20.map_with_index do |i| # uses 20 squares to form bridge
      # sets x by multiplying 64 to index to find pixel value (places all squares side by side)
      # subtracts 64 from bridge_top because position is denoted by bottom left corner
      [i * 64, args.state.bridge_top - 64, 64, 64]
    end
  
    args.outputs.solids << [args.state.x, args.state.y, args.state.w, args.state.h, 255, 0, 0]
    args.outputs.solids << [args.state.player.x, args.state.player.y, args.state.player.w, args.state.player.h, 255, 0, 0] # outputs player onto screen (red box)
    args.outputs.solids << [args.state.enemy.x, args.state.enemy.y, args.state.enemy.w, args.state.enemy.h, 0, 255, 0] # outputs enemy onto screen (green box)
    args.outputs.solids << args.state.enemy.hammers # outputs enemy's hammers onto screen
  end
  
  # Performs calculations to move objects on the screen
  def calc args
  
    # Since velocity is the change in position, the change in x increases by dx. Same with y and dy.
    args.state.player.x  += args.state.player.dx
    args.state.player.y  += args.state.player.dy
  
    # Since acceleration is the change in velocity, the change in y (dy) increases every frame
    args.state.player.dy += args.state.gravity
  
    # player's y position is either current y position or y position of top of
    # bridge, whichever has a greater value
    # ensures that the player never goes below the bridge
    args.state.player.y  = args.state.player.y.greater(args.state.bridge_top)
  
    # player's x position is either the current x position or 0, whichever has a greater value
    # ensures that the player doesn't go too far left (out of the screen's scope)
    args.state.player.x  = args.state.player.x.greater(0)
  
    # player is not falling if it is located on the top of the bridge
    args.state.player.falling = false if args.state.player.y == args.state.bridge_top
    args.state.player.rect = [args.state.player.x, args.state.player.y, args.state.player.h, args.state.player.w] # sets definition for player
  
    args.state.enemy.x += args.state.enemy.dx # velocity; change in x increases by dx
    args.state.enemy.y += args.state.enemy.dy # same with y and dy
  
    # ensures that the enemy never goes below the bridge
    args.state.enemy.y  = args.state.enemy.y.greater(args.state.bridge_top)
  
    # ensures that the enemy never goes too far left (outside the screen's scope)
    args.state.enemy.x  = args.state.enemy.x.greater(0)
  
    # objects that go up must come down because of gravity
    args.state.enemy.dy += args.state.gravity
  
    args.state.enemy.y  = args.state.enemy.y.greater(args.state.bridge_top)
  
    #sets definition of enemy
    args.state.enemy.rect = [args.state.enemy.x, args.state.enemy.y, args.state.enemy.h, args.state.enemy.w]
  
    if args.state.enemy.y == args.state.bridge_top # if enemy is located on the top of the bridge
      args.state.enemy.dy = 0 # there is no change in y
    end
  
    # if 60 frames have passed and the enemy is not moving vertically
    if args.state.tick_count.mod_zero?(args.state.enemy_jump_interval) && args.state.enemy.dy == 0
      args.state.enemy.dy = args.state.enemy_jump_power # the enemy jumps up
    end
  
    # if 40 frames have passed or 5 frames have passed since the game ended
    if args.state.tick_count.mod_zero?(args.state.hammer_throw_interval) || args.state.game_over_at.elapsed_time == 5
      # rand will return a number greater than or equal to 0 and less than given variable's value (since max is excluded)
      # that is why we're adding 1, to include the max possibility
      volley_dx   = (rand(args.state.hammer_launch_power_default) + 1) * -1 # horizontal movement (follow order of operations)
  
      # if the horizontal distance between the player and enemy is less than 128 pixels
      if (args.state.player.x - args.state.enemy.x).abs < 128
        # the change in x won't be that great since the enemy and player are closer to each other
        volley_dx = (rand(args.state.hammer_launch_power_near) + 1) * -1
      end
  
      # if the horizontal distance between the player and enemy is greater than 300 pixels
      if (args.state.player.x - args.state.enemy.x).abs > 300
        # change in x will be more drastic since player and enemy are so far apart
        volley_dx = (rand(args.state.hammer_launch_power_far) + 1) * -1 # more drastic change
      end
  
      (rand(args.state.max_hammers_per_volley) + 1).map_with_index do |i|
        args.state.enemy.hammer_queue << { # stores hammer values in a hash
          x: args.state.enemy.x,
          w: args.state.hammer_size,
          h: args.state.hammer_size,
          dx: volley_dx, # change in horizontal position
          # multiplication operator takes precedence over addition operator
          throw_at: args.state.tick_count + i * args.state.gap_between_hammers
        }
      end
    end
  
    # add elements from hammer_queue collection to the hammers collection by
    # finding all hammers that were thrown before the current frame (have already been thrown)
    args.state.enemy.hammers += args.state.enemy.hammer_queue.find_all do |h|
      h[:throw_at] < args.state.tick_count
    end
  
    args.state.enemy.hammers.each do |h| # sets values for all hammers in collection
      h[:y]  ||= args.state.enemy.y + 130
      h[:dy] ||= args.state.hammer_upward_launch_power
      h[:dy]  += args.state.gravity # acceleration is change in gravity
      h[:x]   += h[:dx] # incremented by change in position
      h[:y]   += h[:dy]
      h[:rect] = [h[:x], h[:y], h[:w], h[:h]] # sets definition of hammer's rect
    end
  
    # reject hammers that have been thrown before current frame (have already been thrown)
    args.state.enemy.hammer_queue = args.state.enemy.hammer_queue.reject do |h|
      h[:throw_at] < args.state.tick_count
    end
  
    # any hammers with a y position less than 0 are rejected from the hammers collection
    # since they have gone too far down (outside the scope's screen)
    args.state.enemy.hammers = args.state.enemy.hammers.reject { |h| h[:y] < 0 }
  
    # if there are any hammers that intersect with (or hit) the player,
    # the reset_player method is called (so the game can start over)
    if args.state.enemy.hammers.any? { |h| h[:rect].intersect_rect?(args.state.player.rect) }
      reset_player args
    end
  
    # if the enemy's rect intersects with (or hits) the player,
    # the reset_player method is called (so the game can start over)
    if args.state.enemy.rect.intersect_rect? args.state.player.rect
      reset_player args
    end
  end
  
  # Resets the player by changing its properties back to the values they had at initialization
  def reset_player args
    args.state.player.x = 0
    args.state.player.y = args.state.bridge_top
    args.state.player.dy = 0
    args.state.player.dx = 0
    args.state.enemy.hammers.clear # empties hammer collection
    args.state.enemy.hammer_queue.clear # empties hammer_queue
    args.state.game_over_at = args.state.tick_count # game_over_at set to current frame (or passage of time)
  end
  
  # Processes input from the user to move the player
  def input args
    if args.inputs.keyboard.space # if the user presses the space bar
      args.state.player.jumped_at ||= args.state.tick_count # jumped_at is set to current frame
  
      # if the time that has passed since the jump is less than the player's jump duration and
      # the player is not falling
      if args.state.player.jumped_at.elapsed_time < args.state.player_jump_power_duration && !args.state.player.falling
        args.state.player.dy = args.state.player_jump_power # change in y is set to power of player's jump
      end
    end
  
    # if the space bar is in the "up" state (or not being pressed down)
    if args.inputs.keyboard.key_up.space
      args.state.player.jumped_at = nil # jumped_at is empty
      args.state.player.falling = true # the player is falling
    end
  
    if args.inputs.keyboard.left # if left key is pressed
      args.state.player.dx -= args.state.player_acceleration # dx decreases by acceleration (player goes left)
      # dx is either set to current dx or the negative max run speed (which would be -10),
      # whichever has a greater value
      args.state.player.dx = args.state.player.dx.greater(-args.state.player_max_run_speed)
    elsif args.inputs.keyboard.right # if right key is pressed
      args.state.player.dx += args.state.player_acceleration # dx increases by acceleration (player goes right)
      # dx is either set to current dx or max run speed (which would be 10),
      # whichever has a lesser value
      args.state.player.dx = args.state.player.dx.lesser(args.state.player_max_run_speed)
    else
      args.state.player.dx *= args.state.player_speed_slowdown_rate # dx is scaled down
    end
  end
  
  def tick_instructions args, text, y = 715
    return if args.state.key_event_occurred
    if args.inputs.mouse.click ||
       args.inputs.keyboard.directional_vector ||
       args.inputs.keyboard.key_down.enter ||
       args.inputs.keyboard.key_down.space ||
       args.inputs.keyboard.key_down.escape
      args.state.key_event_occurred = true
    end
  
    args.outputs.debug << [0, y - 50, 1280, 60].solid
    args.outputs.debug << [640, y, text, 1, 1, 255, 255, 255].label
    args.outputs.debug << [640, y - 25, "(click to dismiss instructions)" , -2, 1, 255, 255, 255].label
  end

#+end_src

*** Physics And Collisions - Entities - main.rb
#+begin_src ruby
  # ./samples/04_physics_and_collisions/03_entities/app/main.rb
  =begin
  
   Reminders:
  
   - map: Ruby method used to transform data; used in arrays, hashes, and collections.
     Can be used to perform an action on every element of a collection, such as multiplying
     each element by 2 or declaring every element as a new entity.
  
   - reject: Removes elements from a collection if they meet certain requirements.
     For example, you can derive an array of odd numbers from an original array of
     numbers 1 through 10 by rejecting all elements that are even (or divisible by 2).
  
   - args.state.new_entity: Used when we want to create a new object, like a sprite or button.
     In this sample app, new_entity is used to define the properties of enemies and bullets.
     (Remember, you can use state to define ANY property and it will be retained across frames.)
  
   - args.outputs.labels: An array. The values generate a label on the screen.
     The parameters are [X, Y, TEXT, SIZE, ALIGN, RED, GREEN, BLUE, ALPHA, FONT STYLE]
  
   - ARRAY#intersect_rect?: Returns true or false depending on if the two rectangles intersect.
  
   - args.inputs.mouse.click.point.(x|y): The x and y location of the mouse.
  
  =end
  
  # This sample app shows enemies that contain an id value and the time they were created.
  # These enemies can be removed by shooting at them with bullets.
  
  # Calls all methods necessary for the game to function properly.
  def tick args
    tick_instructions args, "Sample app shows how to use args.state.new_entity along with collisions. CLICK to shoot a bullet."
    defaults args
    render args
    calc args
    process_inputs args
  end
  
  # Sets default values
  # Enemies and bullets start off as empty collections
  def defaults args
    args.state.enemies ||= []
    args.state.bullets ||= []
  end
  
  # Provides each enemy in enemies collection with rectangular border,
  # as well as a label showing id and when they were created
  def render args
    # When you're calling a method that takes no arguments, you can use this & syntax on map.
    # Numbers are being added to x and y in order to keep the text within the enemy's borders.
    args.outputs.borders << args.state.enemies.map(&:rect)
    args.outputs.labels  << args.state.enemies.flat_map do |enemy|
      [
        [enemy.x + 4, enemy.y + 29, "id: #{enemy.entity_id}", -3, 0],
        [enemy.x + 4, enemy.y + 17, "created_at: #{enemy.created_at}", -3, 0] # frame enemy was created
      ]
    end
  
    # Outputs bullets in bullets collection as rectangular solids
    args.outputs.solids << args.state.bullets.map(&:rect)
  end
  
  # Calls all methods necessary for performing calculations
  def calc args
    add_new_enemies_if_needed args
    move_bullets args
    calculate_collisions args
    remove_bullets_of_screen args
  end
  
  # Adds enemies to the enemies collection and sets their values
  def add_new_enemies_if_needed args
    return if args.state.enemies.length >= 10 # if 10 or more enemies, enemies are not added
    return unless args.state.bullets.length == 0 # if user has not yet shot bullet, no enemies are added
  
    args.state.enemies += (10 - args.state.enemies.length).map do # adds enemies so there are 10 total
      args.state.new_entity(:enemy) do |e| # each enemy is declared as a new entity
        e.x = 640 + 500 * rand # each enemy is given random position on screen
        e.y = 600 * rand + 50
        e.rect = [e.x, e.y, 130, 30] # sets definition for enemy's rect
      end
    end
  end
  
  # Moves bullets across screen
  # Sets definition of the bullets
  def move_bullets args
    args.state.bullets.each do |bullet| # perform action on each bullet in collection
      bullet.x += bullet.speed # increment x by speed (bullets fly horizontally across screen)
  
      # By randomizing the value that increments bullet.y, the bullet does not fly straight up and out
      # of the scope of the screen. Try removing what follows bullet.speed, or changing 0.25 to 1.25 to
      # see what happens to the bullet's movement.
      bullet.y += bullet.speed.*(0.25).randomize(:ratio, :sign)
      bullet.rect = [bullet.x, bullet.y, bullet.size, bullet.size] # sets definition of bullet's rect
    end
  end
  
  # Determines if a bullet hits an enemy
  def calculate_collisions args
    args.state.bullets.each do |bullet| # perform action on every bullet and enemy in collections
      args.state.enemies.each do |enemy|
        # if bullet has not exploded yet and the bullet hits an enemy
        if !bullet.exploded && bullet.rect.intersect_rect?(enemy.rect)
          bullet.exploded = true # bullet explodes
          enemy.dead = true # enemy is killed
        end
      end
    end
  
    # All exploded bullets are rejected or removed from the bullets collection
    # and any dead enemy is rejected from the enemies collection.
    args.state.bullets = args.state.bullets.reject(&:exploded)
    args.state.enemies = args.state.enemies.reject(&:dead)
  end
  
  # Bullets are rejected from bullets collection once their position exceeds the width of screen
  def remove_bullets_of_screen args
    args.state.bullets = args.state.bullets.reject { |bullet| bullet.x > 1280 } # screen width is 1280
  end
  
  # Calls fire_bullet method
  def process_inputs args
    fire_bullet args
  end
  
  # Once mouse is clicked by the user to fire a bullet, a new bullet is added to bullets collection
  def fire_bullet args
    return unless args.inputs.mouse.click # return unless mouse is clicked
    args.state.bullets << args.state.new_entity(:bullet) do |bullet| # new bullet is declared a new entity
      bullet.y = args.inputs.mouse.click.point.y # set to the y value of where the mouse was clicked
      bullet.x = 0 # starts on the left side of the screen
      bullet.size = 10
      bullet.speed = 10 * rand + 2 # speed of a bullet is randomized
      bullet.rect = [bullet.x, bullet.y, bullet.size, bullet.size] # definition is set
    end
  end
  
  def tick_instructions args, text, y = 715
    return if args.state.key_event_occurred
    if args.inputs.mouse.click ||
       args.inputs.keyboard.directional_vector ||
       args.inputs.keyboard.key_down.enter ||
       args.inputs.keyboard.key_down.space ||
       args.inputs.keyboard.key_down.escape
      args.state.key_event_occurred = true
    end
  
    args.outputs.debug << [0, y - 50, 1280, 60].solid
    args.outputs.debug << [640, y, text, 1, 1, 255, 255, 255].label
    args.outputs.debug << [640, y - 25, "(click to dismiss instructions)" , -2, 1, 255, 255, 255].label
  end

#+end_src

*** Physics And Collisions - Box Collision - main.rb
#+begin_src ruby
  # ./samples/04_physics_and_collisions/04_box_collision/app/main.rb
  =begin
  
   APIs listing that haven't been encountered in previous sample apps:
  
   - first: Returns the first element of the array.
     For example, if we have an array
     numbers = [1, 2, 3, 4, 5]
     and we call first by saying
     numbers.first
     the number 1 will be returned because it is the first element of the numbers array.
  
   - num1.idiv(num2): Divides two numbers and returns an integer.
     For example,
     16.idiv(3) = 5, because 16 / 3 is 5.33333 returned as an integer.
     16.idiv(4) = 4, because 16 / 4 is 4 and already has no decimal.
  
   Reminders:
  
   - find_all: Finds all values that satisfy specific requirements.
  
   - ARRAY#intersect_rect?: An array with at least four values is
     considered a rect. The intersect_rect? function returns true
     or false depending on if the two rectangles intersect.
  
   - reject: Removes elements from a collection if they meet certain requirements.
  
  =end
  
  # This sample app allows users to create tiles and place them anywhere on the screen as obstacles.
  # The player can then move and maneuver around them.
  
  class PoorManPlatformerPhysics
    attr_accessor :grid, :inputs, :state, :outputs
  
    # Calls all methods necessary for the app to run successfully.
    def tick
      defaults
      render
      calc
      process_inputs
    end
  
    # Sets default values for variables.
    # The ||= sign means that the variable will only be set to the value following the = sign if the value has
    # not already been set before. Intialization happens only in the first frame.
    def defaults
      state.tile_size               = 64
      state.gravity                 = -0.2
      state.previous_tile_size    ||= state.tile_size
      state.x                     ||= 0
      state.y                     ||= 800
      state.dy                    ||= 0
      state.dx                    ||= 0
      state.world                 ||= []
      state.world_lookup          ||= {}
      state.world_collision_rects ||= []
    end
  
    # Outputs solids and borders of different colors for the world and collision_rects collections.
    def render
  
      # Sets a black background on the screen (Comment this line out and the background will become white.)
      # Also note that black is the default color for when no color is assigned.
      outputs.solids << grid.rect
  
      # The position, size, and color (white) are set for borders given to the world collection.
      # Try changing the color by assigning different numbers (between 0 and 255) to the last three parameters.
      outputs.borders << state.world.map do |x, y|
        [x * state.tile_size,
         y * state.tile_size,
         state.tile_size,
         state.tile_size, 255, 255, 255]
      end
  
      # The top, bottom, and sides of the borders for collision_rects are different colors.
      outputs.borders << state.world_collision_rects.map do |e|
        [
          [e[:top],                             0, 170,   0], # top is a shade of green
          [e[:bottom],                          0, 100, 170], # bottom is a shade of greenish-blue
          [e[:left_right],                    170,   0,   0], # left and right are a shade of red
        ]
      end
  
      # Sets the position, size, and color (a shade of green) of the borders of only the player's
      # box and outputs it. If you change the 180 to 0, the player's box will be black and you
      # won't be able to see it (because it will match the black background).
      outputs.borders << [state.x,
                          state.y,
                          state.tile_size,
                          state.tile_size,  0, 180, 0]
    end
  
    # Calls methods needed to perform calculations.
    def calc
      calc_world_lookup
      calc_player
    end
  
    # Performs calculations on world_lookup and sets values.
    def calc_world_lookup
  
      # If the tile size isn't equal to the previous tile size,
      # the previous tile size is set to the tile size,
      # and world_lookup hash is set to empty.
      if state.tile_size != state.previous_tile_size
        state.previous_tile_size = state.tile_size
        state.world_lookup = {} # empty hash
      end
  
      # return if the world_lookup hash has keys (or, in other words, is not empty)
      # return unless the world collection has values inside of it (or is not empty)
      return if state.world_lookup.keys.length > 0
      return unless state.world.length > 0
  
      # Starts with an empty hash for world_lookup.
      # Searches through the world and finds the coordinates that exist.
      state.world_lookup = {}
      state.world.each { |x, y| state.world_lookup[[x, y]] = true }
  
      # Assigns world_collision_rects for every sprite drawn.
      state.world_collision_rects =
        state.world_lookup
            .keys
            .map do |coord_x, coord_y|
              s = state.tile_size
              # multiply by tile size so the grid coordinates; sets pixel value
              # don't forget that position is denoted by bottom left corner
              # set x = coord_x or y = coord_y and see what happens!
              x = s * coord_x
              y = s * coord_y
              {
                # The values added to x, y, and s position the world_collision_rects so they all appear
                # stacked (on top of world rects) but don't directly overlap.
                # Remove these added values and mess around with the rect placement!
                args:       [coord_x, coord_y],
                left_right: [x,     y + 4, s,     s - 6], # hash keys and values
                top:        [x + 4, y + 6, s - 8, s - 6],
                bottom:     [x + 1, y - 1, s - 2, s - 8],
              }
            end
    end
  
    # Performs calculations to change the x and y values of the player's box.
    def calc_player
  
      # Since acceleration is the change in velocity, the change in y (dy) increases every frame.
      # What goes up must come down because of gravity.
      state.dy += state.gravity
  
      # Calls the calc_box_collision and calc_edge_collision methods.
      calc_box_collision
      calc_edge_collision
  
      # Since velocity is the change in position, the change in y increases by dy. Same with x and dx.
      state.y += state.dy
      state.x += state.dx
  
      # Scales dx down.
      state.dx *= 0.8
    end
  
    # Calls methods needed to determine collisions between player and world_collision rects.
    def calc_box_collision
      return unless state.world_lookup.keys.length > 0 # return unless hash has atleast 1 key
      collision_floor!
      collision_left!
      collision_right!
      collision_ceiling!
    end
  
    # Finds collisions between the bottom of the player's rect and the top of a world_collision_rect.
    def collision_floor!
      return unless state.dy <= 0 # return unless player is going down or is as far down as possible
      player_rect = [state.x, state.y - 0.1, state.tile_size, state.tile_size] # definition of player
  
      # Goes through world_collision_rects to find all intersections between the bottom of player's rect and
      # the top of a world_collision_rect (hence the "-0.1" above)
      floor_collisions = state.world_collision_rects
                             .find_all { |r| r[:top].intersect_rect?(player_rect, collision_tollerance) }
                             .first
  
      return unless floor_collisions # return unless collision occurred
      state.y = floor_collisions[:top].top # player's y is set to the y of the top of the collided rect
      state.dy = 0 # if a collision occurred, the player's rect isn't moving because its path is blocked
    end
  
    # Finds collisions between the player's left side and the right side of a world_collision_rect.
    def collision_left!
      return unless state.dx < 0 # return unless player is moving left
      player_rect = [state.x - 0.1, state.y, state.tile_size, state.tile_size]
  
      # Goes through world_collision_rects to find all intersections beween the player's left side and the
      # right side of a world_collision_rect.
      left_side_collisions = state.world_collision_rects
                                 .find_all { |r| r[:left_right].intersect_rect?(player_rect, collision_tollerance) }
                                 .first
  
      return unless left_side_collisions # return unless collision occurred
  
      # player's x is set to the value of the x of the collided rect's right side
      state.x = left_side_collisions[:left_right].right
      state.dx = 0 # player isn't moving left because its path is blocked
    end
  
    # Finds collisions between the right side of the player and the left side of a world_collision_rect.
    def collision_right!
      return unless state.dx > 0 # return unless player is moving right
      player_rect = [state.x + 0.1, state.y, state.tile_size, state.tile_size]
  
      # Goes through world_collision_rects to find all intersections between the player's right side
      # and the left side of a world_collision_rect (hence the "+0.1" above)
      right_side_collisions = state.world_collision_rects
                                  .find_all { |r| r[:left_right].intersect_rect?(player_rect, collision_tollerance) }
                                  .first
  
      return unless right_side_collisions # return unless collision occurred
  
      # player's x is set to the value of the collided rect's left, minus the size of a rect
      # tile size is subtracted because player's position is denoted by bottom left corner
      state.x = right_side_collisions[:left_right].left - state.tile_size
      state.dx = 0 # player isn't moving right because its path is blocked
    end
  
    # Finds collisions between the top of the player's rect and the bottom of a world_collision_rect.
    def collision_ceiling!
      return unless state.dy > 0 # return unless player is moving up
      player_rect = [state.x, state.y + 0.1, state.tile_size, state.tile_size]
  
      # Goes through world_collision_rects to find intersections between the bottom of a
      # world_collision_rect and the top of the player's rect (hence the "+0.1" above)
      ceil_collisions = state.world_collision_rects
                            .find_all { |r| r[:bottom].intersect_rect?(player_rect, collision_tollerance) }
                            .first
  
      return unless ceil_collisions # return unless collision occurred
  
      # player's y is set to the bottom y of the rect it collided with, minus the size of a rect
      state.y = ceil_collisions[:bottom].y - state.tile_size
      state.dy = 0 # if a collision occurred, the player isn't moving up because its path is blocked
    end
  
    # Makes sure the player remains within the screen's dimensions.
    def calc_edge_collision
  
      #Ensures that the player doesn't fall below the map.
      if state.y < 0
        state.y = 0
        state.dy = 0
  
      #Ensures that the player doesn't go too high.
      # Position of player is denoted by bottom left hand corner, which is why we have to subtract the
      # size of the player's box (so it remains visible on the screen)
      elsif state.y > 720 - state.tile_size # if the player's y position exceeds the height of screen
        state.y = 720 - state.tile_size # the player will remain as high as possible while staying on screen
        state.dy = 0
      end
  
      # Ensures that the player remains in the horizontal range that it is supposed to.
      if state.x >= 1280 - state.tile_size && state.dx > 0 # if player moves too far right
        state.x = 1280 - state.tile_size # player will remain as right as possible while staying on screen
        state.dx = 0
      elsif state.x <= 0 && state.dx < 0 # if player moves too far left
        state.x = 0 # player will remain as left as possible while remaining on screen
        state.dx = 0
      end
    end
  
    # Processes input from the user on the keyboard.
    def process_inputs
      if inputs.mouse.down
        state.world_lookup = {}
        x, y = to_coord inputs.mouse.down.point  # gets x, y coordinates for the grid
  
        if state.world.any? { |loc| loc == [x, y] }  # checks if coordinates duplicate
          state.world = state.world.reject { |loc| loc == [x, y] }  # erases tile space
        else
          state.world << [x, y] # If no duplicates, adds to world collection
        end
      end
  
      # Sets dx to 0 if the player lets go of arrow keys.
      if inputs.keyboard.key_up.right
        state.dx = 0
      elsif inputs.keyboard.key_up.left
        state.dx = 0
      end
  
      # Sets dx to 3 in whatever direction the player chooses.
      if inputs.keyboard.key_held.right # if right key is pressed
        state.dx =  3
      elsif inputs.keyboard.key_held.left # if left key is pressed
        state.dx = -3
      end
  
      #Sets dy to 5 to make the player ~fly~ when they press the space bar
      if inputs.keyboard.key_held.space
        state.dy = 5
      end
    end
  
    def to_coord point
  
      # Integer divides (idiv) point.x to turn into grid
      # Then, you can just multiply each integer by state.tile_size later so the grid coordinates.
      [point.x.idiv(state.tile_size), point.y.idiv(state.tile_size)]
    end
  
    # Represents the tolerance for a collision between the player's rect and another rect.
    def collision_tollerance
      0.0
    end
  end
  
  $platformer_physics = PoorManPlatformerPhysics.new
  
  def tick args
    $platformer_physics.grid    = args.grid
    $platformer_physics.inputs  = args.inputs
    $platformer_physics.state    = args.state
    $platformer_physics.outputs = args.outputs
    $platformer_physics.tick
    tick_instructions args, "Sample app shows platformer collisions. CLICK to place box. ARROW keys to move around. SPACE to jump."
  end
  
  def tick_instructions args, text, y = 715
    return if args.state.key_event_occurred
    if args.inputs.mouse.click ||
       args.inputs.keyboard.directional_vector ||
       args.inputs.keyboard.key_down.enter ||
       args.inputs.keyboard.key_down.escape
      args.state.key_event_occurred = true
    end
  
    args.outputs.debug << [0, y - 50, 1280, 60].solid
    args.outputs.debug << [640, y, text, 1, 1, 255, 255, 255].label
    args.outputs.debug << [640, y - 25, "(click to dismiss instructions)" , -2, 1, 255, 255, 255].label
  end

#+end_src

*** Physics And Collisions - Box Collision 2 - main.rb
#+begin_src ruby
  # ./samples/04_physics_and_collisions/05_box_collision_2/app/main.rb
  =begin
   APIs listing that haven't been encountered in previous sample apps:
  
   - times: Performs an action a specific number of times.
     For example, if we said
     5.times puts "Hello DragonRuby",
     then we'd see the words "Hello DragonRuby" printed on the console 5 times.
  
   - split: Divides a string into substrings based on a delimiter.
     For example, if we had a command
     "DragonRuby is awesome".split(" ")
     then the result would be
     ["DragonRuby", "is", "awesome"] because the words are separated by a space delimiter.
  
   - join: Opposite of split; converts each element of array to a string separated by delimiter.
     For example, if we had a command
     ["DragonRuby","is","awesome"].join(" ")
     then the result would be
     "DragonRuby is awesome".
  
   Reminders:
  
   - to_s: Returns a string representation of an object.
     For example, if we had
     500.to_s
     the string "500" would be returned.
     Similar to to_i, which returns an integer representation of an object.
  
   - elapsed_time: How many frames have passed since the click event.
  
   - args.outputs.labels: An array. Values in the array generate labels on the screen.
     The parameters are: [X, Y, TEXT, SIZE, ALIGN, RED, GREEN, BLUE, ALPHA, FONT STYLE]
     For more information about labels, go to mygame/documentation/02-labels.md.
  
   - inputs.mouse.down: Determines whether or not the mouse is being pressed down.
     The position of the mouse when it is pressed down can be found using inputs.mouse.down.point.(x|y).
  
   - first: Returns the first element of the array.
  
   - num1.idiv(num2): Divides two numbers and returns an integer.
  
   - find_all: Finds all values that satisfy specific requirements.
  
   - ARRAY#intersect_rect?: Returns true or false depending on if two rectangles intersect.
  
   - reject: Removes elements from a collection if they meet certain requirements.
  
   - String interpolation: Uses #{} syntax; everything between the #{ and the } is evaluated
     as Ruby code, and the placeholder is replaced with its corresponding value or result.
  
  =end
  
  MAP_FILE_PATH = 'app/map.txt' # the map.txt file in the app folder contains exported map
  
  class MetroidvaniaStarter
    attr_accessor :grid, :inputs, :state, :outputs, :gtk
  
    # Calls methods needed to run the game properly.
    def tick
      defaults
      render
      calc
      process_inputs
    end
  
    # Sets all the default variables.
    # '||' states that initialization occurs only in the first frame.
    def defaults
      state.tile_size                = 64
      state.gravity                  = -0.2
      state.player_width             = 60
      state.player_height            = 64
      state.collision_tolerance      = 0.0
      state.previous_tile_size     ||= state.tile_size
      state.x                      ||= 0
      state.y                      ||= 800
      state.dy                     ||= 0
      state.dx                     ||= 0
      attempt_load_world_from_file
      state.world_lookup           ||= { }
      state.world_collision_rects  ||= []
      state.mode                   ||= :creating # alternates between :creating and :selecting for sprite selection
      state.select_menu            ||= [0, 720, 1280, 720]
      #=======================================IMPORTANT=======================================#
      # When adding sprites, please label them "image1.png", "image2.png", image3".png", etc.
      # Once you have done that, adjust "state.sprite_quantity" to how many sprites you have.
      #=======================================================================================#
      state.sprite_quantity        ||= 20 # IMPORTANT TO ALTER IF SPRITES ADDED IF YOU ADD MORE SPRITES
      state.sprite_coords          ||= []
      state.banner_coords          ||= [640, 680 + 720]
      state.sprite_selected        ||= 1
      state.map_saved_at           ||= 0
  
      # Sets all the cordinate values for the sprite selection screen into a grid
      # Displayed when 's' is pressed by player to access sprites
      if state.sprite_coords == [] # if sprite_coords is an empty array
        count = 1
        temp_x = 165 # sets a starting x and y position for display
        temp_y = 500 + 720
        state.sprite_quantity.times do # for the number of sprites you have
          state.sprite_coords += [[temp_x, temp_y, count]] # add element to sprite_coords array
          temp_x += 100 # increment temp_x
          count += 1 # increment count
          if temp_x > 1280 - (165 + 50) # if exceeding specific horizontal width on screen
            temp_x = 165 # a new row of sprites starts
            temp_y -= 75 # new row of sprites starts 75 units lower than the previous row
          end
        end
      end
    end
  
    # Places sprites
    def render
  
      # Sets the x, y, width, height, and image path for each sprite in the world collection.
      outputs.sprites << state.world.map do |x, y, sprite|
        [x * state.tile_size, # multiply by size so grid coordinates; pixel value of location
         y * state.tile_size,
         state.tile_size,
         state.tile_size,
         'sprites/image' + sprite.to_s + '.png'] # uses concatenation to create unique image path
      end
  
      # Outputs sprite for the player by setting x, y, width, height, and image path
      outputs.sprites << [state.x,
                          state.y,
                          state.player_width,
                          state.player_height,'sprites/player.png']
  
      # Outputs labels as primitives in top right of the screen
      outputs.primitives << [920, 700, 'Press \'s\' to access sprites.', 1, 0].label
      outputs.primitives << [920, 675, 'Click existing sprite to delete.', 1, 0].label
  
      outputs.primitives << [920, 640, '<- and -> to move.', 1, 0].label
      outputs.primitives << [920, 615, 'Press and hold space to jump.', 1, 0].label
  
      outputs.primitives << [920, 580, 'Press \'e\' to export current map.', 1, 0].label
  
      # if the map is saved and less than 120 frames have passed, the label is displayed
      if state.map_saved_at > 0 && state.map_saved_at.elapsed_time < 120
        outputs.primitives << [920, 555, 'Map has been exported!', 1, 0, 50, 100, 50].label
      end
  
      # If player hits 's', following appears
      if state.mode == :selecting
        # White background for sprite selection
        outputs.primitives << [state.select_menu, 255, 255, 255].solid
  
        # Select tile label at the top of the screen
        outputs.primitives << [state.banner_coords.x, state.banner_coords.y, "Select Sprite (sprites located in \"sprites\" folder)", 10, 1, 0, 0, 0, 255].label
  
        # Places sprites in locations calculated in the defaults function
        outputs.primitives << state.sprite_coords.map do |x, y, order|
          [x, y, 50, 50, 'sprites/image' + order.to_s + ".png"].sprite
        end
      end
  
      # Creates sprite following mouse to help indicate which sprite you have selected
      # 10 is subtracted from the mouse's x position so that the sprite is not covered by the mouse icon
      outputs.primitives << [inputs.mouse.position.x - 10, inputs.mouse.position.y,
                             10, 10, 'sprites/image' + state.sprite_selected.to_s + ".png"].sprite
    end
  
    # Calls methods that perform calculations
    def calc
      calc_in_game
      calc_sprite_selection
    end
  
    # Calls methods that perform calculations (if in creating mode)
    def calc_in_game
      return unless state.mode == :creating
      calc_world_lookup
      calc_player
    end
  
    def calc_world_lookup
      # If the tile size isn't equal to the previous tile size,
      # the previous tile size is set to the tile size,
      # and world_lookup hash is set to empty.
      if state.tile_size != state.previous_tile_size
        state.previous_tile_size = state.tile_size
        state.world_lookup = {}
      end
  
      # return if world_lookup is not empty or if world is empty
      return if state.world_lookup.keys.length > 0
      return unless state.world.length > 0
  
      # Searches through the world and finds the coordinates that exist
      state.world_lookup = {}
      state.world.each { |x, y| state.world_lookup[[x, y]] = true }
  
      # Assigns collision rects for every sprite drawn
      state.world_collision_rects =
        state.world_lookup
             .keys
             .map do |coord_x, coord_y|
               s = state.tile_size
               # Multiplying by s (the size of a tile) ensures that the rect is
               # placed exactly where you want it to be placed (causes grid to coordinate)
               # How many pixels horizontally across and vertically up and down
               x = s * coord_x
               y = s * coord_y
               {
                 args:       [coord_x, coord_y],
                 left_right: [x,     y + 4, s,     s - 6], # hash keys and values
                 top:        [x + 4, y + 6, s - 8, s - 6],
                 bottom:     [x + 1, y - 1, s - 2, s - 8],
               }
             end
    end
  
    # Calculates movement of player and calls methods that perform collision calculations
    def calc_player
      state.dy += state.gravity  # what goes up must come down because of gravity
      calc_box_collision
      calc_edge_collision
      state.y  += state.dy       # Since velocity is the change in position, the change in y increases by dy
      state.x  += state.dx       # Ditto line above but dx and x
      state.dx *= 0.8            # Scales dx down
    end
  
    # Calls methods that determine whether the player collides with any world_collision_rects.
    def calc_box_collision
      return unless state.world_lookup.keys.length > 0 # return unless hash has atleast 1 key
      collision_floor
      collision_left
      collision_right
      collision_ceiling
    end
  
    # Finds collisions between the bottom of the player's rect and the top of a world_collision_rect.
    def collision_floor
      return unless state.dy <= 0 # return unless player is going down or is as far down as possible
      player_rect = [state.x, next_y, state.tile_size, state.tile_size] # definition of player
  
      # Runs through all the sprites on the field and finds all intersections between player's
      # bottom and the top of a rect.
      floor_collisions = state.world_collision_rects
                           .find_all { |r| r[:top].intersect_rect?(player_rect, state.collision_tolerance) }
                           .first
  
      return unless floor_collisions # performs following changes if a collision has occurred
      state.y = floor_collisions[:top].top # y of player is set to the y of the colliding rect's top
      state.dy = 0 # no change in y because the player's path is blocked
    end
  
    # Finds collisions between the player's left side and the right side of a world_collision_rect.
    def collision_left
      return unless state.dx < 0 # return unless player is moving left
      player_rect = [next_x, state.y, state.tile_size, state.tile_size]
  
      # Runs through all the sprites on the field and finds all intersections between the player's left side
      # and the right side of a rect.
      left_side_collisions = state.world_collision_rects
                               .find_all { |r| r[:left_right].intersect_rect?(player_rect, state.collision_tolerance) }
                               .first
  
      return unless left_side_collisions # return unless collision occurred
      state.x = left_side_collisions[:left_right].right # sets player's x to the x of the colliding rect's right side
      state.dx = 0 # no change in x because the player's path is blocked
    end
  
    # Finds collisions between the right side of the player and the left side of a world_collision_rect.
    def collision_right
      return unless state.dx > 0 # return unless player is moving right
      player_rect = [next_x, state.y, state.tile_size, state.tile_size]
  
      # Runs through all the sprites on the field and finds all intersections between the  player's
      # right side and the left side of a rect.
      right_side_collisions = state.world_collision_rects
                                .find_all { |r| r[:left_right].intersect_rect?(player_rect, state.collision_tolerance) }
                                .first
  
      return unless right_side_collisions # return unless collision occurred
      state.x = right_side_collisions[:left_right].left - state.tile_size # player's x is set to the x of colliding rect's left side (minus tile size since x is the player's bottom left corner)
      state.dx = 0 # no change in x because the player's path is blocked
    end
  
    # Finds collisions between the top of the player's rect and the bottom of a world_collision_rect.
    def collision_ceiling
      return unless state.dy > 0 # return unless player is moving up
      player_rect = [state.x, next_y, state.player_width, state.player_height]
  
      # Runs through all the sprites on the field and finds all intersections between the player's top
      # and the bottom of a rect.
      ceil_collisions = state.world_collision_rects
                          .find_all { |r| r[:bottom].intersect_rect?(player_rect, state.collision_tolerance) }
                          .first
  
      return unless ceil_collisions # return unless collision occurred
      state.y = ceil_collisions[:bottom].y - state.tile_size # player's y is set to the y of the colliding rect's bottom (minus tile size)
      state.dy = 0 # no change in y because the player's path is blocked
    end
  
    # Makes sure the player remains within the screen's dimensions.
    def calc_edge_collision
      # Ensures that player doesn't fall below the map
      if next_y < 0 && state.dy < 0 # if player is moving down and is about to fall (next_y) below the map's scope
        state.y = 0 # 0 is the lowest the player can be while staying on the screen
        state.dy = 0
      # Ensures player doesn't go insanely high
      elsif next_y > 720 - state.tile_size && state.dy > 0 # if player is moving up, about to exceed map's scope
        state.y = 720 - state.tile_size # if we don't subtract tile_size, we won't be able to see the player on the screen
        state.dy = 0
      end
  
      # Ensures that player remains in the horizontal range its supposed to
      if state.x >= 1280 - state.tile_size && state.dx > 0 # if the player is moving too far right
        state.x = 1280 - state.tile_size # farthest right the player can be while remaining in the screen's scope
        state.dx = 0
      elsif state.x <= 0 && state.dx < 0 # if the player is moving too far left
        state.x = 0 # farthest left the player can be while remaining in the screen's scope
        state.dx = 0
      end
    end
  
    def calc_sprite_selection
      # Does the transition to bring down the select sprite screen
      if state.mode == :selecting && state.select_menu.y != 0
        state.select_menu.y = 0  # sets y position of select menu (shown when 's' is pressed)
        state.banner_coords.y = 680 # sets y position of Select Sprite banner
        state.sprite_coords = state.sprite_coords.map do |x, y, w, h|
          [x, y - 720, w, h] # sets definition of sprites (change '-' to '+' and the sprites can't be seen)
        end
      end
  
      # Does the transition to leave the select sprite screen
      if state.mode == :creating  && state.select_menu.y != 720
        state.select_menu.y = 720 # sets y position of select menu (menu is retreated back up)
        state.banner_coords.y = 1000 # sets y position of Select Sprite banner
        state.sprite_coords = state.sprite_coords.map do |x, y, w, h|
          [x, y + 720, w, h] # sets definition of all elements in collection
        end
      end
    end
  
    def process_inputs
      # If the state.mode is back and if the menu has retreated back up
      # call methods that process user inputs
      if state.mode == :creating
        process_inputs_player_movement
        process_inputs_place_tile
      end
  
      # For each sprite_coordinate added, check what sprite was selected
      if state.mode == :selecting
        state.sprite_coords.map do |x, y, order| # goes through all sprites in collection
          # checks that a specific sprite was pressed based on x, y position
          if inputs.mouse.down && # the && (and) sign means ALL statements must be true for the evaluation to be true
             inputs.mouse.down.point.x >= x      && # x is greater than or equal to sprite's x and
             inputs.mouse.down.point.x <= x + 50 && # x is less than or equal to 50 pixels to the right
             inputs.mouse.down.point.y >= y      && # y is greater than or equal to sprite's y
             inputs.mouse.down.point.y <= y + 50 # y is less than or equal to 50 pixels up
            state.sprite_selected = order # sprite is chosen
          end
        end
      end
  
      inputs_export_stage
      process_inputs_show_available_sprites
    end
  
    # Moves the player based on the keys they press on their keyboard
    def process_inputs_player_movement
      # Sets dx to 0 if the player lets go of arrow keys (player won't move left or right)
      if inputs.keyboard.key_up.right
        state.dx = 0
      elsif inputs.keyboard.key_up.left
        state.dx = 0
      end
  
      # Sets dx to 3 in whatever direction the player chooses when they hold down (or press) the left or right keys
      if inputs.keyboard.key_held.right
        state.dx =  3
      elsif inputs.keyboard.key_held.left
        state.dx = -3
      end
  
      # Sets dy to 5 to make the player ~fly~ when they press the space bar on their keyboard
      if inputs.keyboard.key_held.space
        state.dy = 5
      end
    end
  
    # Adds tile in the place the user holds down the mouse
    def process_inputs_place_tile
      if inputs.mouse.down # if mouse is pressed
        state.world_lookup = {}
        x, y = to_coord inputs.mouse.down.point # gets x, y coordinates for the grid
  
        # Checks if any coordinates duplicate (already exist in world)
        if state.world.any? { |existing_x, existing_y, n| existing_x == x && existing_y == y }
          #erases existing tile space by rejecting them from world
          state.world = state.world.reject do |existing_x, existing_y, n|
            existing_x == x && existing_y == y
          end
        else
          state.world << [x, y, state.sprite_selected] # If no duplicates, add the sprite
        end
      end
    end
  
    # Stores/exports world collection's info (coordinates, sprite number) into a file
    def inputs_export_stage
      if inputs.keyboard.key_down.e # if "e" is pressed
        export_string = state.world.map do |x, y, sprite_number| # stores world info in a string
          "#{x},#{y},#{sprite_number}"                           # using string interpolation
        end
        gtk.write_file(MAP_FILE_PATH, export_string.join("\n")) # writes string into a file
        state.map_saved_at = state.tick_count # frame number (passage of time) when the map was saved
      end
    end
  
    def process_inputs_show_available_sprites
      # Based on keyboard input, the entity (:creating and :selecting) switch
      if inputs.keyboard.key_held.s && state.mode == :creating # if "s" is pressed and currently creating
        state.mode = :selecting # will change to selecting
        inputs.keyboard.clear # VERY IMPORTANT! If not present, it'll flicker between on and off
      elsif inputs.keyboard.key_held.s && state.mode == :selecting # if "s" is pressed and currently selecting
        state.mode = :creating # will change to creating
        inputs.keyboard.clear # VERY IMPORTANT! If not present, it'll flicker between on and off
      end
    end
  
    # Loads the world collection by reading from the map.txt file in the app folder
    def attempt_load_world_from_file
      return if state.world # return if the world collection is already populated
      state.world ||= [] # initialized as an empty collection
      exported_world = gtk.read_file(MAP_FILE_PATH) # reads the file using the path mentioned at top of code
      return unless exported_world # return unless the file read was successful
      state.world = exported_world.each_line.map do |l| # perform action on each line of exported_world
          l.split(',').map(&:to_i) # calls split using ',' as a delimiter, and invokes .map on the collection,
                                   # calling to_i (converts to integers) on each element
      end
    end
  
    # Adds the change in y to y to determine the next y position of the player.
    def next_y
      state.y + state.dy
    end
  
    # Determines next x position of player
    def next_x
      if state.dx < 0 # if the player moves left
        return state.x - (state.tile_size - state.player_width) # subtracts since the change in x is negative (player is moving left)
      else
        return state.x + (state.tile_size - state.player_width) # adds since the change in x is positive (player is moving right)
      end
    end
  
    def to_coord point
      # Integer divides (idiv) point.x to turn into grid
      # Then, you can just multiply each integer by state.tile_size
      # later and huzzah. Grid coordinates
      [point.x.idiv(state.tile_size), point.y.idiv(state.tile_size)]
    end
  end
  
  $metroidvania_starter = MetroidvaniaStarter.new
  
  def tick args
      $metroidvania_starter.grid    = args.grid
      $metroidvania_starter.inputs  = args.inputs
      $metroidvania_starter.state   = args.state
      $metroidvania_starter.outputs = args.outputs
      $metroidvania_starter.gtk     = args.gtk
      $metroidvania_starter.tick
  end

#+end_src

*** Physics And Collisions - Box Collision 3 - main.rb
#+begin_src ruby
  # ./samples/04_physics_and_collisions/06_box_collision_3/app/main.rb
  class Game
    attr_gtk
  
    def tick
      defaults
      render
      input_edit_map
      input_player
      calc_player
    end
  
    def defaults
      state.gravity           = -0.4
      state.drag              = 0.15
      state.tile_size         = 32
      state.player.size       = 16
      state.player.jump_power = 12
  
      state.tiles                 ||= []
      state.player.y              ||= 800
      state.player.x              ||= 100
      state.player.dy             ||= 0
      state.player.dx             ||= 0
      state.player.jumped_down_at ||= 0
      state.player.jumped_at      ||= 0
  
      calc_player_rect if !state.player.rect
    end
  
    def render
      outputs.labels << [10, 10.from_top, "tile: click to add a tile, hold X key and click to delete a tile."]
      outputs.labels << [10, 35.from_top, "move: use left and right to move, space to jump, down and space to jump down."]
      outputs.labels << [10, 55.from_top, "      You can jump through or jump down through tiles with a height of 1."]
      outputs.background_color = [80, 80, 80]
      outputs.sprites << tiles.map(&:sprite)
      outputs.sprites << (player.rect.merge path: 'sprites/square/green.png')
  
      mouse_overlay = {
        x: (inputs.mouse.x.ifloor state.tile_size),
        y: (inputs.mouse.y.ifloor state.tile_size),
        w: state.tile_size,
        h: state.tile_size,
        a: 100
      }
  
      mouse_overlay = mouse_overlay.merge r: 255 if state.delete_mode
  
      if state.mouse_held
        outputs.primitives << mouse_overlay.border!
      else
        outputs.primitives << mouse_overlay.solid!
      end
    end
  
    def input_edit_map
      state.mouse_held = true  if inputs.mouse.down
      state.mouse_held = false if inputs.mouse.up
  
      if inputs.keyboard.x
        state.delete_mode = true
      elsif inputs.keyboard.key_up.x
        state.delete_mode = false
      end
  
      return unless state.mouse_held
  
      ordinal = { x: (inputs.mouse.x.idiv state.tile_size),
                  y: (inputs.mouse.y.idiv state.tile_size) }
  
      found = find_tile ordinal
      if !found && !state.delete_mode
        tiles << (state.new_entity :tile, ordinal)
        recompute_tiles
      elsif found && state.delete_mode
        tiles.delete found
        recompute_tiles
      end
    end
  
    def input_player
      player.dx += inputs.left_right
  
      if inputs.keyboard.key_down.space && inputs.keyboard.down
        player.dy             = player.jump_power * -1
        player.jumped_at      = 0
        player.jumped_down_at = state.tick_count
      elsif inputs.keyboard.key_down.space
        player.dy             = player.jump_power
        player.jumped_at      = state.tick_count
        player.jumped_down_at = 0
      end
    end
  
    def calc_player
      calc_player_rect
      calc_below
      calc_left
      calc_right
      calc_above
      calc_player_dy
      calc_player_dx
      reset_player if player_off_stage?
    end
  
    def calc_player_rect
      player.rect      = current_player_rect
      player.next_rect = player.rect.merge x: player.x + player.dx,
                                           y: player.y + player.dy
      player.prev_rect = player.rect.merge x: player.x - player.dx,
                                           y: player.y - player.dy
    end
  
    def calc_below
      return unless player.dy <= 0
      tiles_below = find_tiles { |t| t.rect.top <= player.prev_rect.y }
      collision = find_colliding_tile tiles_below, (player.rect.merge y: player.next_rect.y)
      return unless collision
      if collision.neighbors.b == :none && player.jumped_down_at.elapsed_time < 10
        player.dy = -1
      else
        player.y  = collision.rect.y + state.tile_size
        player.dy = 0
      end
    end
  
    def calc_left
      return unless player.dx < 0
      tiles_left = find_tiles { |t| t.rect.right <= player.prev_rect.left }
      collision = find_colliding_tile tiles_left, (player.rect.merge x: player.next_rect.x)
      return unless collision
      player.x  = collision.rect.right
      player.dx = 0
    end
  
    def calc_right
      return unless player.dx > 0
      tiles_right = find_tiles { |t| t.rect.left >= player.prev_rect.right }
      collision = find_colliding_tile tiles_right, (player.rect.merge x: player.next_rect.x)
      return unless collision
      player.x  = collision.rect.left - player.rect.w
      player.dx = 0
    end
  
    def calc_above
      return unless player.dy > 0
      tiles_above = find_tiles { |t| t.rect.y >= player.prev_rect.y }
      collision = find_colliding_tile tiles_above, (player.rect.merge y: player.next_rect.y)
      return unless collision
      return if collision.neighbors.t == :none
      player.dy = 0
      player.y  = collision.rect.bottom - player.rect.h
    end
  
    def calc_player_dx
      player.dx  = player.dx.clamp(-5,  5)
      player.dx *= 0.9
      player.x  += player.dx
    end
  
    def calc_player_dy
      player.y  += player.dy
      player.dy += state.gravity
      player.dy += player.dy * state.drag ** 2 * -1
    end
  
    def reset_player
      player.x  = 100
      player.y  = 720
      player.dy = 0
    end
  
    def recompute_tiles
      tiles.each do |t|
        t.w = state.tile_size
        t.h = state.tile_size
        t.neighbors = tile_neighbors t, tiles
  
        t.rect = [t.x * state.tile_size,
                  t.y * state.tile_size,
                  state.tile_size,
                  state.tile_size].rect.to_hash
  
        sprite_sub_path = t.neighbors.mask.map { |m| flip_bit m }.join("")
  
        t.sprite = {
          x: t.x * state.tile_size,
          y: t.y * state.tile_size,
          w: state.tile_size,
          h: state.tile_size,
          path: "sprites/tile/wall-#{sprite_sub_path}.png"
        }
      end
    end
  
    def flip_bit bit
      return 0 if bit == 1
      return 1
    end
  
    def player
      state.player
    end
  
    def player_off_stage?
      player.rect.top < grid.bottom ||
      player.rect.right < grid.left ||
      player.rect.left > grid.right
    end
  
    def current_player_rect
      { x: player.x, y: player.y, w: player.size, h: player.size }
    end
  
    def tiles
      state.tiles
    end
  
    def find_tile ordinal
      tiles.find { |t| t.x == ordinal.x && t.y == ordinal.y }
    end
  
    def find_tiles &block
      tiles.find_all(&block)
    end
  
    def find_colliding_tile tiles, target
      tiles.find { |t| t.rect.intersect_rect? target }
    end
  
    def tile_neighbors tile, other_points
      t = find_tile x: tile.x + 0, y: tile.y + 1
      r = find_tile x: tile.x + 1, y: tile.y + 0
      b = find_tile x: tile.x + 0, y: tile.y - 1
      l = find_tile x: tile.x - 1, y: tile.y + 0
  
      tile_t, tile_r, tile_b, tile_l = 0
  
      tile_t = 1 if t
      tile_r = 1 if r
      tile_b = 1 if b
      tile_l = 1 if l
  
      state.new_entity :neighbors, mask: [tile_t, tile_r, tile_b, tile_l],
                                   t:    t ? :some : :none,
                                   b:    b ? :some : :none,
                                   l:    l ? :some : :none,
                                   r:    r ? :some : :none
    end
  end
  
  def tick args
    $game ||= Game.new
    $game.args = args
    $game.tick
  end

#+end_src

*** Physics And Collisions - Jump Physics - main.rb
#+begin_src ruby
  # ./samples/04_physics_and_collisions/07_jump_physics/app/main.rb
  =begin
  
   Reminders:
  
   - args.state.new_entity: Used when we want to create a new object, like a sprite or button.
     For example, if we want to create a new button, we would declare it as a new entity and
     then define its properties. (Remember, you can use state to define ANY property and it will
     be retained across frames.)
  
   - args.outputs.solids: An array. The values generate a solid.
     The parameters for a solid are [X, Y, WIDTH, HEIGHT, RED, GREEN, BLUE]
     For more information about solids, go to mygame/documentation/03-solids-and-borders.md.
  
   - num1.greater(num2): Returns the greater value.
  
   - Hashes: Collection of unique keys and their corresponding values. The value can be found
     using their keys.
  
   - ARRAY#inside_rect?: Returns true or false depending on if the point is inside the rect.
  
  =end
  
  # This sample app is a game that requires the user to jump from one platform to the next.
  # As the player successfully clears platforms, they become smaller and move faster.
  
  class VerticalPlatformer
    attr_gtk
  
    # declares vertical platformer as new entity
    def s
      state.vertical_platformer ||= state.new_entity(:vertical_platformer)
      state.vertical_platformer
    end
  
    # creates a new platform using a hash
    def new_platform hash
      s.new_entity_strict(:platform, hash) # platform key
    end
  
    # calls methods needed for game to run properly
    def tick
      defaults
      render
      calc
      input
    end
  
    def init_game
      s.platforms ||= [ # initializes platforms collection with two platforms using hashes
        new_platform(x: 0, y: 0, w: 700, h: 32, dx: 1, speed: 0, rect: nil),
        new_platform(x: 0, y: 300, w: 700, h: 32, dx: 1, speed: 0, rect: nil), # 300 pixels higher
      ]
  
      s.tick_count  = args.state.tick_count
      s.gravity     = -0.3 # what goes up must come down because of gravity
      s.player.platforms_cleared ||= 0 # counts how many platforms the player has successfully cleared
      s.player.x  ||= 0           # sets player values
      s.player.y  ||= 100
      s.player.w  ||= 64
      s.player.h  ||= 64
      s.player.dy ||= 0           # change in position
      s.player.dx ||= 0
      s.player_jump_power           = 15
      s.player_jump_power_duration  = 10
      s.player_max_run_speed        = 5
      s.player_speed_slowdown_rate  = 0.9
      s.player_acceleration         = 1
      s.camera ||= { y: -100 } # shows view on screen (as the player moves upward, the camera does too)
    end
  
    # Sets default values
    def defaults
      init_game
    end
  
    # Outputs objects onto the screen
    def render
      outputs.solids << s.platforms.map do |p| # outputs platforms onto screen
        [p.x + 300, p.y - s.camera[:y], p.w, p.h] # add 300 to place platform in horizontal center
        # don't forget, position of platform is denoted by bottom left hand corner
      end
  
      # outputs player using hash
      outputs.solids << {
        x: s.player.x + 300, # player positioned on top of platform
        y: s.player.y - s.camera[:y],
        w: s.player.w,
        h: s.player.h,
        r: 100,              # color saturation
        g: 100,
        b: 200
      }
    end
  
    # Performs calculations
    def calc
      s.platforms.each do |p| # for each platform in the collection
        p.rect = [p.x, p.y, p.w, p.h] # set the definition
      end
  
      # sets player point by adding half the player's width to the player's x
      s.player.point = [s.player.x + s.player.w.half, s.player.y] # change + to - and see what happens!
  
      # search the platforms collection to find if the player's point is inside the rect of a platform
      collision = s.platforms.find { |p| s.player.point.inside_rect? p.rect }
  
      # if collision occurred and player is moving down (or not moving vertically at all)
      if collision && s.player.dy <= 0
        s.player.y = collision.rect.y + collision.rect.h - 2 # player positioned on top of platform
        s.player.dy = 0 if s.player.dy < 0 # player stops moving vertically
        if !s.player.platform
          s.player.dx = 0 # no horizontal movement
        end
        # changes horizontal position of player by multiplying collision change in x (dx) by speed and adding it to current x
        s.player.x += collision.dx * collision.speed
        s.player.platform = collision # player is on the platform that it collided with (or landed on)
        if s.player.falling # if player is falling
          s.player.dx = 0  # no horizontal movement
        end
        s.player.falling = false
        s.player.jumped_at = nil
      else
        s.player.platform = nil # player is not on a platform
        s.player.y  += s.player.dy # velocity is the change in position
        s.player.dy += s.gravity # acceleration is the change in velocity; what goes up must come down
      end
  
      s.platforms.each do |p| # for each platform in the collection
        p.x += p.dx * p.speed # x is incremented by product of dx and speed (causes platform to move horizontally)
        # changes platform's x so it moves left and right across the screen (between -300 and 300 pixels)
        if p.x < -300 # if platform goes too far left
          p.dx *= -1 # dx is scaled down
          p.x = -300 # as far left as possible within scope
        elsif p.x > (1000 - p.w) # if platform's x is greater than 300
          p.dx *= -1
          p.x = (1000 - p.w) # set to 300 (as far right as possible within scope)
        end
      end
  
      delta = (s.player.y - s.camera[:y] - 100) # used to position camera view
  
      if delta > -200
        s.camera[:y] += delta * 0.01 # allows player to see view as they move upwards
        s.player.x  += s.player.dx # velocity is change in position; change in x increases by dx
  
        # searches platform collection to find platforms located more than 300 pixels above the player
        has_platforms = s.platforms.find { |p| p.y > (s.player.y + 300) }
        if !has_platforms # if there are no platforms 300 pixels above the player
          width = 700 - (700 * (0.1 * s.player.platforms_cleared)) # the next platform is smaller than previous
          s.player.platforms_cleared += 1 # player successfully cleared another platform
          last_platform = s.platforms[-1] # platform just cleared becomes last platform
          # another platform is created 300 pixels above the last platform, and this
          # new platform has a smaller width and moves faster than all previous platforms
          s.platforms << new_platform(x: (700 - width) * rand, # random x position
                                      y: last_platform.y + 300,
                                      w: width,
                                      h: 32,
                                      dx: 1.randomize(:sign), # random change in x
                                      speed: 2 * s.player.platforms_cleared,
                                      rect: nil)
        end
      else
        # game over
        s.as_hash.clear # otherwise clear the hash (no new platform is necessary)
        init_game
      end
    end
  
    # Takes input from the user to move the player
    def input
      if inputs.keyboard.space # if the space bar is pressed
        s.player.jumped_at ||= s.tick_count # set to current frame
  
        # if the time that has passed since the jump is less than the duration of a jump (10 frames)
        # and the player is not falling
        if s.player.jumped_at.elapsed_time < s.player_jump_power_duration && !s.player.falling
          s.player.dy = s.player_jump_power # player jumps up
        end
      end
  
      if inputs.keyboard.key_up.space # if space bar is in "up" state
        s.player.falling = true # player is falling
      end
  
      if inputs.keyboard.left # if left key is pressed
        s.player.dx -= s.player_acceleration # player's position changes, decremented by acceleration
        s.player.dx = s.player.dx.greater(-s.player_max_run_speed) # dx is either current dx or -5, whichever is greater
      elsif inputs.keyboard.right # if right key is pressed
        s.player.dx += s.player_acceleration # player's position changes, incremented by acceleration
        s.player.dx  = s.player.dx.lesser(s.player_max_run_speed) # dx is either current dx or 5, whichever is lesser
      else
        s.player.dx *= s.player_speed_slowdown_rate # scales dx down
      end
    end
  end
  
  $game = VerticalPlatformer.new
  
  def tick args
    $game.args = args
    $game.tick
  end

#+end_src

*** Physics And Collisions - Bouncing On Collision - ball.rb
#+begin_src ruby
  # ./samples/04_physics_and_collisions/08_bouncing_on_collision/app/ball.rb
  GRAVITY = -0.08
  
  class Ball
      attr_accessor :velocity, :center, :radius, :collision_enabled
  
      def initialize args
          #Start the ball in the top center
          #@x = args.grid.w / 2
          #@y = args.grid.h - 20
  
          @velocity = {x: 0, y: 0}
          #@width =  20
          #@height = @width
          @radius = 20.0 / 2.0
          @center = {x: (args.grid.w / 2), y: (args.grid.h)}
  
          #@left_wall = (args.state.board_width + args.grid.w / 8)
          #@right_wall = @left_wall + args.state.board_width
          @left_wall = 0
          @right_wall = $args.grid.right
  
          @max_velocity = 7
          @collision_enabled = true
      end
  
      #Move the ball according to its velocity
      def update args
        @center.x += @velocity.x
        @center.y += @velocity.y
        @velocity.y += GRAVITY
  
        alpha = 0.2
        if @center.y-@radius <= 0
          @velocity.y  = (@velocity.y.abs*0.7).abs
          @velocity.x  = (@velocity.x.abs*0.9).abs * ((@velocity.x < 0) ? -1 : 1)
  
          if @velocity.y.abs() < alpha
            @velocity.y=0
          end
          if @velocity.x.abs() < alpha
            @velocity.x=0
          end
        end
  
        if @center.x > args.grid.right+@radius*2
          @center.x = 0-@radius
        elsif @center.x< 0-@radius*2
          @center.x = args.grid.right + @radius
        end
      end
  
      def wallBounds args
          #if @x < @left_wall || @x + @width > @right_wall
              #@velocity.x *= -1.1
              #if @velocity.x > @max_velocity
                  #@velocity.x = @max_velocity
              #elsif @velocity.x < @max_velocity * -1
                  #@velocity.x = @max_velocity * -1
              #end
          #end
          #if @y < 0 || @y + @height > args.grid.h
              #@velocity.y *= -1.1
              #if @velocity.y > @max_velocity
                  #@velocity.y = @max_velocity
              #elsif @velocity.y < @max_velocity * -1
                  #@velocity.y = @max_velocity * -1
              #end
          #end
      end
  
      #render the ball to the screen
      def draw args
          #args.outputs.solids << [@x, @y, @width, @height, 255, 255, 0];
          args.outputs.sprites << [
            @center.x-@radius,
            @center.y-@radius,
            @radius*2,
            @radius*2,
            "sprites/circle-white.png",
            0,
            255,
            255,    #r
            0,    #g
            255   #b
          ]
      end
    end

#+end_src

*** Physics And Collisions - Bouncing On Collision - block.rb
#+begin_src ruby
  # ./samples/04_physics_and_collisions/08_bouncing_on_collision/app/block.rb
  DEGREES_TO_RADIANS = Math::PI / 180
  
  class Block
    def initialize(x, y, block_size, rotation)
      @x = x
      @y = y
      @block_size = block_size
      @rotation = rotation
  
      #The repel velocity?
      @velocity = {x: 2, y: 0}
  
      horizontal_offset = (3 * block_size) * Math.cos(rotation * DEGREES_TO_RADIANS)
      vertical_offset = block_size * Math.sin(rotation * DEGREES_TO_RADIANS)
  
      if rotation >= 0
        theta = 90 - rotation
        #The line doesn't visually line up exactly with the edge of the sprite, so artificially move it a bit
        modifier = 5
        x_offset = modifier * Math.cos(theta * DEGREES_TO_RADIANS)
        y_offset = modifier * Math.sin(theta * DEGREES_TO_RADIANS)
        @x1 = @x - x_offset
        @y1 = @y + y_offset
        @x2 = @x1 + horizontal_offset
        @y2 = @y1 + (vertical_offset * 3)
  
        @imaginary_line = [ @x1, @y1, @x2, @y2 ]
      else
        theta = 90 + rotation
        x_offset = @block_size * Math.cos(theta * DEGREES_TO_RADIANS)
        y_offset = @block_size * Math.sin(theta * DEGREES_TO_RADIANS)
        @x1 = @x + x_offset
        @y1 = @y + y_offset + 19
        @x2 = @x1 + horizontal_offset
        @y2 = @y1 + (vertical_offset * 3)
  
        @imaginary_line = [ @x1, @y1, @x2, @y2 ]
      end
  
    end
  
    def draw args
      args.outputs.sprites << [
        @x,
        @y,
        @block_size*3,
        @block_size,
        "sprites/square-green.png",
        @rotation
      ]
  
      args.outputs.lines << @imaginary_line
      args.outputs.solids << @debug_shape
    end
  
    def multiply_matricies
    end
  
    def calc args
      if collision? args
          collide args
      end
    end
  
    #Determine if the ball and block are touching
    def collision? args
      #The minimum area enclosed by the center of the ball and the 2 corners of the block
      #If the area ever drops below this value, we know there is a collision
      min_area = ((@block_size * 3) * args.state.ball.radius) / 2
  
      #https://www.mathopenref.com/coordtrianglearea.html
      ax = @x1
      ay = @y1
      bx = @x2
      by = @y2
      cx = args.state.ball.center.x
      cy = args.state.ball.center.y
  
      current_area = (ax*(by-cy)+bx*(cy-ay)+cx*(ay-by))/2
  
      collision = false
      if @rotation >= 0
        if (current_area < min_area &&
          current_area > 0 &&
          args.state.ball.center.y > @y1 &&
          args.state.ball.center.x < @x2)
  
          collision = true
        end
      else
        if (current_area < min_area &&
          current_area > 0 &&
          args.state.ball.center.y > @y2 &&
          args.state.ball.center.x > @x1)
  
        collision = true
        end
      end
  
      return collision
    end
  
    def collide args
      #Slope of the block
      slope = (@y2 - @y1) / (@x2 - @x1)
  
      #Create a unit vector and tilt it (@rotation) number of degrees
      x = -Math.cos(@rotation * DEGREES_TO_RADIANS)
      y = Math.sin(@rotation * DEGREES_TO_RADIANS)
  
      #Find the vector that is perpendicular to the slope
      perpVect = { x: x, y: y }
      mag  = (perpVect.x**2 + perpVect.y**2)**0.5                                 # find the magniude of the perpVect
      perpVect = {x: perpVect.x/(mag), y: perpVect.y/(mag)}                       # divide the perpVect by the magniude to make it a unit vector
  
      previousPosition = {                                                        # calculate an ESTIMATE of the previousPosition of the ball
        x:args.state.ball.center.x-args.state.ball.velocity.x,
        y:args.state.ball.center.y-args.state.ball.velocity.y
      }
  
      velocityMag = (args.state.ball.velocity.x**2 + args.state.ball.velocity.y**2)**0.5 # the current velocity magnitude of the ball
      theta_ball = Math.atan2(args.state.ball.velocity.y, args.state.ball.velocity.x)         #the angle of the ball's velocity
      theta_repel = (180 * DEGREES_TO_RADIANS) - theta_ball + (@rotation * DEGREES_TO_RADIANS)
  
      fbx = velocityMag * Math.cos(theta_ball)                                    #the x component of the ball's velocity
      fby = velocityMag * Math.sin(theta_ball)                                    #the y component of the ball's velocity
  
      frx = velocityMag * Math.cos(theta_repel)                                       #the x component of the repel's velocity | magnitude is set to twice of fbx
      fry = velocityMag * Math.sin(theta_repel)                                       #the y component of the repel's velocity | magnitude is set to twice of fby
  
      args.state.display_value = velocityMag
      fsumx = fbx+frx                                                             #sum of x forces
      fsumy = fby+fry                                                             #sum of y forces
      fr = velocityMag                                                            #fr is the resulting magnitude
      thetaNew = Math.atan2(fsumy, fsumx)                                         #thetaNew is the resulting angle
  
      xnew = fr*Math.cos(thetaNew)                                                #resulting x velocity
      ynew = fr*Math.sin(thetaNew)                                                #resulting y velocity
  
      dampener = 0.3
      ynew *= dampener * 0.5
  
      #If the bounce is very low, that means the ball is rolling and we don't want to dampenen the X velocity
      if ynew > -0.1
        xnew *= dampener
      end
  
      #Add the sine component of gravity back in (X component)
      gravity_x = 4 * Math.sin(@rotation * DEGREES_TO_RADIANS)
      xnew += gravity_x
  
      args.state.ball.velocity.x = -xnew
      args.state.ball.velocity.y = -ynew
  
      #Set the position of the ball to the previous position so it doesn't warp throught the block
      args.state.ball.center.x = previousPosition.x
      args.state.ball.center.y = previousPosition.y
    end
  end

#+end_src

*** Physics And Collisions - Bouncing On Collision - cannon.rb
#+begin_src ruby
  # ./samples/04_physics_and_collisions/08_bouncing_on_collision/app/cannon.rb
  class Cannon
    def initialize args
      @pointA = {x: args.grid.right/2,y: args.grid.top}
      @pointB = {x: args.inputs.mouse.x, y: args.inputs.mouse.y}
    end
    def update args
      activeBall = args.state.ball
      @pointB = {x: args.inputs.mouse.x, y: args.inputs.mouse.y}
  
      if args.inputs.mouse.click
        alpha = 0.01
        activeBall.velocity.y = (@pointB.y - @pointA.y) * alpha
        activeBall.velocity.x = (@pointB.x - @pointA.x) * alpha
        activeBall.center = {x: (args.grid.w / 2), y: (args.grid.h)}
      end
    end
    def render args
      args.outputs.lines << [@pointA.x, @pointA.y, @pointB.x, @pointB.y]
    end
  end

#+end_src

*** Physics And Collisions - Bouncing On Collision - main.rb
#+begin_src ruby
  # ./samples/04_physics_and_collisions/08_bouncing_on_collision/app/main.rb
  INFINITY= 10**10
  
  require 'app/vector2d.rb'
  require 'app/peg.rb'
  require 'app/block.rb'
  require 'app/ball.rb'
  require 'app/cannon.rb'
  
  
  #Method to init default values
  def defaults args
    args.state.pegs ||= []
    args.state.blocks ||= []
    args.state.cannon ||= Cannon.new args
    args.state.ball ||= Ball.new args
    args.state.horizontal_offset ||= 0
    init_pegs args
    init_blocks args
  
    args.state.display_value ||= "test"
  end
  
  begin :default_methods
    def init_pegs args
      num_horizontal_pegs = 14
      num_rows = 5
  
      return unless args.state.pegs.count < num_rows * num_horizontal_pegs
  
      block_size = 32
      block_spacing = 50
      total_width = num_horizontal_pegs * (block_size + block_spacing)
      starting_offset = (args.grid.w - total_width) / 2 + block_size
  
      for i in (0...num_rows)
        for j in (0...num_horizontal_pegs)
          row_offset = 0
          if i % 2 == 0
            row_offset = 20
          else
            row_offset = -20
          end
          args.state.pegs.append(Peg.new(j * (block_size+block_spacing) + starting_offset + row_offset, (args.grid.h - block_size * 2) - (i * block_size * 2)-90, block_size))
        end
      end
  
    end
  
    def init_blocks args
      return unless args.state.blocks.count < 10
  
      #Sprites are rotated in degrees, but the Ruby math functions work on radians
      radians_to_degrees = Math::PI / 180
  
      block_size = 25
      #Rotation angle (in degrees) of the blocks
      rotation = 30
      vertical_offset = block_size * Math.sin(rotation * radians_to_degrees)
      horizontal_offset = (3 * block_size) * Math.cos(rotation * radians_to_degrees)
      center = args.grid.w / 2
  
      for i in (0...5)
        #Create a ramp of blocks. Not going to be perfect because of the float to integer conversion and anisotropic to isotropic coversion
        args.state.blocks.append(Block.new((center + 100 + (i * horizontal_offset)).to_i, 100 + (vertical_offset * i) + (i * block_size), block_size, rotation))
        args.state.blocks.append(Block.new((center - 100 - (i * horizontal_offset)).to_i, 100 + (vertical_offset * i) + (i * block_size), block_size, -rotation))
      end
    end
  end
  
  #Render loop
  def render args
    args.outputs.borders << args.state.game_area
    render_pegs args
    render_blocks args
    args.state.cannon.render args
    args.state.ball.draw args
  end
  
  begin :render_methods
    #Draw the pegs in a grid pattern
    def render_pegs args
      args.state.pegs.each do |peg|
        peg.draw args
      end
    end
  
    def render_blocks args
      args.state.blocks.each do |block|
        block.draw args
      end
    end
  
  end
  
  #Calls all methods necessary for performing calculations
  def calc args
    args.state.pegs.each do |peg|
      peg.calc args
    end
  
    args.state.blocks.each do |block|
      block.calc args
    end
  
    args.state.ball.update args
    args.state.cannon.update args
  end
  
  begin :calc_methods
  
  end
  
  def tick args
    defaults args
    render args
    calc args
  end

#+end_src

*** Physics And Collisions - Bouncing On Collision - peg.rb
#+begin_src ruby
  # ./samples/04_physics_and_collisions/08_bouncing_on_collision/app/peg.rb
  class Peg
    def initialize(x, y, block_size)
      @x = x                    # x cordinate of the LEFT side of the peg
      @y = y                    # y cordinate of the RIGHT side of the peg
      @block_size = block_size  # diameter of the peg
  
      @radius = @block_size/2.0 # radius of the peg
      @center = {               # cordinatees of the CENTER of the peg
        x: @x+@block_size/2.0,
        y: @y+@block_size/2.0
      }
  
      @r = 255 # color of the peg
      @g = 0
      @b = 0
  
      @velocity = {x: 2, y: 0}
    end
  
    def draw args
      args.outputs.sprites << [ # draw the peg according to the @x, @y, @radius, and the RGB
        @x,
        @y,
        @radius*2.0,
        @radius*2.0,
        "sprites/circle-white.png",
        0,
        255,
        @r,    #r
        @g,    #g
        @b   #b
      ]
    end
  
  
    def calc args
      if collisionWithBounce? args # if the is a collision with the bouncing ball
        collide args
        @r = 0
        @b = 0
        @g = 255
      else
      end
    end
  
  
    # do two circles (the ball and this peg) intersect
    def collisionWithBounce? args
      squareDistance = (  # the squared distance between the ball's center and this peg's center
        (args.state.ball.center.x - @center.x) ** 2.0 +
        (args.state.ball.center.y - @center.y) ** 2.0
      )
      radiusSum = (  # the sum of the radius squared of the this peg and the ball
        (args.state.ball.radius + @radius) ** 2.0
      )
      # if the squareDistance is less or equal to radiusSum, then there is a radial intersection between the ball and this peg
      return (squareDistance <= radiusSum)
    end
  
    # ! The following links explain the getRepelMagnitude function !
    # https://raw.githubusercontent.com/DragonRuby/dragonruby-game-toolkit-physics/master/docs/docImages/LinearCollider_4.png
    # https://raw.githubusercontent.com/DragonRuby/dragonruby-game-toolkit-physics/master/docs/docImages/LinearCollider_5.png
    # https://github.com/DragonRuby/dragonruby-game-toolkit-physics/blob/master/docs/LinearCollider.md
    def getRepelMagnitude (args, fbx, fby, vrx, vry, ballMag)
      a = fbx ; b = vrx ; c = fby
      d = vry ; e = ballMag
      if b**2 + d**2 == 0
        #unexpected
      end
  
      x1 = (-a*b+-c*d + (e**2 * b**2 - b**2 * c**2 + 2*a*b*c*d + e**2 + d**2 - a**2 * d**2)**0.5)/(b**2 + d**2)
      x2 = -((a*b + c*d + (e**2 * b**2 - b**2 * c**2 + 2*a*b*c*d + e**2 * d**2 - a**2 * d**2)**0.5)/(b**2 + d**2))
  
      err = 0.00001
      o = ((fbx + x1*vrx)**2 + (fby + x1*vry)**2 ) ** 0.5
      p = ((fbx + x2*vrx)**2 + (fby + x2*vry)**2 ) ** 0.5
      r = 0
  
      if (ballMag >= o-err and ballMag <= o+err)
        r = x1
      elsif (ballMag >= p-err and ballMag <= p+err)
        r = x2
      else
        #unexpected
      end
  
      if (args.state.ball.center.x > @center.x)
        return x2*-1
      end
  
      return x2
  
      #return r
    end
  
    #this sets the new velocity of the ball once it has collided with this peg
    def collide args
      normalOfRCCollision = [                                                     #this is the normal of the collision in COMPONENT FORM
        {x: @center.x, y: @center.y},                                             #see https://www.google.com/url?sa=i&url=https%3A%2F%2Fwww.mathscard.co.uk%2Fonline%2Fcircle-coordinate-geometry%2F&psig=AOvVaw2GcD-e2-nJR_IUKpw3hO98&ust=1605731315521000&source=images&cd=vfe&ved=0CAIQjRxqFwoTCMjBo7e1iu0CFQAAAAAdAAAAABAD
        {x: args.state.ball.center.x, y: args.state.ball.center.y},
      ]
  
      normalSlope = (                                                             #normalSlope is the slope of normalOfRCCollision
        (normalOfRCCollision[1].y - normalOfRCCollision[0].y) /
        (normalOfRCCollision[1].x - normalOfRCCollision[0].x)
      )
      slope = normalSlope**-1.0 * -1                                              # slope is the slope of the tangent
      # args.state.display_value = slope
      pointA = {                                                                  # pointA and pointB are using the var slope to tangent in COMPONENT FORM
        x: args.state.ball.center.x-1,
        y: -(slope-args.state.ball.center.y)
      }
      pointB = {
        x: args.state.ball.center.x+1,
        y: slope+args.state.ball.center.y
      }
  
      perpVect = {x: pointB.x - pointA.x, y:pointB.y - pointA.y}                  # perpVect is to be VECTOR of the perpendicular tangent
      mag  = (perpVect.x**2 + perpVect.y**2)**0.5                                 # find the magniude of the perpVect
      perpVect = {x: perpVect.x/(mag), y: perpVect.y/(mag)}                       # divide the perpVect by the magniude to make it a unit vector
      perpVect = {x: -perpVect.y, y: perpVect.x}                                  # swap the x and y and multiply by -1 to make the vector perpendicular
      args.state.display_value = perpVect
      if perpVect.y > 0                                                           #ensure perpVect points upward
        perpVect = {x: perpVect.x*-1, y: perpVect.y*-1}
      end
  
      previousPosition = {                                                        # calculate an ESTIMATE of the previousPosition of the ball
        x:args.state.ball.center.x-args.state.ball.velocity.x,
        y:args.state.ball.center.y-args.state.ball.velocity.y
      }
  
      yInterc = pointA.y + -slope*pointA.x
      if slope == INFINITY                                                        # the perpVect presently either points in the correct dirrection or it is 180 degrees off we need to correct this
        if previousPosition.x < pointA.x
          perpVect = {x: perpVect.x*-1, y: perpVect.y*-1}
          yInterc = -INFINITY
        end
      elsif previousPosition.y < slope*previousPosition.x + yInterc               # check if ball is bellow or above the collider to determine if perpVect is - or +
        perpVect = {x: perpVect.x*-1, y: perpVect.y*-1}
      end
  
      velocityMag =                                                               # the current velocity magnitude of the ball
        (args.state.ball.velocity.x**2 + args.state.ball.velocity.y**2)**0.5
      theta_ball=
        Math.atan2(args.state.ball.velocity.y,args.state.ball.velocity.x)         #the angle of the ball's velocity
      theta_repel=
        Math.atan2(args.state.ball.center.y,args.state.ball.center.x)             #the angle of the repelling force(perpVect)
  
      fbx = velocityMag * Math.cos(theta_ball)                                    #the x component of the ball's velocity
      fby = velocityMag * Math.sin(theta_ball)                                    #the y component of the ball's velocity
      repelMag = getRepelMagnitude(                                               # the magniude of the collision vector
        args,
        fbx,
        fby,
        perpVect.x,
        perpVect.y,
        (args.state.ball.velocity.x**2 + args.state.ball.velocity.y**2)**0.5
      )
      frx = repelMag* Math.cos(theta_repel)                                       #the x component of the repel's velocity | magnitude is set to twice of fbx
      fry = repelMag* Math.sin(theta_repel)                                       #the y component of the repel's velocity | magnitude is set to twice of fby
  
      fsumx = fbx+frx                            # sum of x forces
      fsumy = fby+fry                            # sum of y forces
      fr = velocityMag                           # fr is the resulting magnitude
      thetaNew = Math.atan2(fsumy, fsumx)        # thetaNew is the resulting angle
      xnew = fr*Math.cos(thetaNew)               # resulting x velocity
      ynew = fr*Math.sin(thetaNew)               # resulting y velocity
      if (args.state.ball.center.x >= @center.x) # this is necessary for the ball colliding on the right side of the peg
        xnew=xnew.abs
      end
  
      args.state.ball.velocity.x = xnew                                           # set the x-velocity to the new velocity
      if args.state.ball.center.y > @center.y                                     # if the ball is above the middle of the peg we need to temporarily ignore some of the gravity
        args.state.ball.velocity.y = ynew + GRAVITY * 0.01
      else
        args.state.ball.velocity.y = ynew - GRAVITY * 0.01                        # if the ball is bellow the middle of the peg we need to temporarily increase the power of the gravity
      end
  
      args.state.ball.center.x+= args.state.ball.velocity.x                       # update the position of the ball so it never looks like the ball is intersecting the circle
      args.state.ball.center.y+= args.state.ball.velocity.y
    end
  end

#+end_src

*** Physics And Collisions - Bouncing On Collision - vector2d.rb
#+begin_src ruby
  # ./samples/04_physics_and_collisions/08_bouncing_on_collision/app/vector2d.rb
  class Vector2d
      attr_accessor :x, :y
    
      def initialize x=0, y=0
        @x=x
        @y=y
      end
    
      #returns a vector multiplied by scalar x
      #x [float] scalar
      def mult x
        r = Vector2d.new(0,0)
        r.x=@x*x
        r.y=@y*x
        r
      end
    
      # vect [Vector2d] vector to copy
      def copy vect
        Vector2d.new(@x, @y)
      end
    
      #returns a new vector equivalent to this+vect
      #vect [Vector2d] vector to add to self
      def add vect
        Vector2d.new(@x+vect.x,@y+vect.y)
      end
    
      #returns a new vector equivalent to this-vect
      #vect [Vector2d] vector to subtract to self
      def sub vect
        Vector2d.new(@x-vect.c, @y-vect.y)
      end
    
      #return the magnitude of the vector
      def mag
        ((@x**2)+(@y**2))**0.5
      end
    
      #returns a new normalize version of the vector
      def normalize
        Vector2d.new(@x/mag, @y/mag)
      end
    
      #TODO delet?
      def distABS vect
        (((vect.x-@x)**2+(vect.y-@y)**2)**0.5).abs()
      end
    end
#+end_src

*** Physics And Collisions - Arbitrary Collision - ball.rb
#+begin_src ruby
  # ./samples/04_physics_and_collisions/09_arbitrary_collision/app/ball.rb
  
  class Ball
      attr_accessor :velocity, :child, :parent, :number, :leastChain
      attr_reader :x, :y, :hypotenuse, :width, :height
  
      def initialize args, number, leastChain, parent, child
          #Start the ball in the top center
          @number = number
          @leastChain = leastChain
          @x = args.grid.w / 2
          @y = args.grid.h - 20
  
          @velocity = Vector2d.new(2, -2)
          @width =  10
          @height = 10
  
          @left_wall = (args.state.board_width + args.grid.w / 8)
          @right_wall = @left_wall + args.state.board_width
  
          @max_velocity = MAX_VELOCITY
  
          @child = child
          @parent = parent
  
          @past = [{x: @x, y: @y}]
          @next = nil
      end
  
      def reassignLeastChain (lc=nil)
        if (lc == nil)
          lc = @number
        end
        @leastChain = lc
        if (parent != nil)
          @parent.reassignLeastChain(lc)
        end
  
      end
  
      def makeLeader args
        if isLeader
          return
        end
        @parent.reassignLeastChain
        args.state.ballParents.push(self)
        @parent = nil
  
      end
  
      def isLeader
        return (parent == nil)
      end
  
      def receiveNext (p)
        #trace!
        if parent != nil
          @x = p[:x]
          @y = p[:y]
          @velocity = p[:velocity]
          #puts @x.to_s + "|" + @y.to_s + "|"+@velocity.to_s
          @past.append(p)
          if (@past.length >= BALL_DISTANCE)
            if (@child != nil)
              @child.receiveNext(@past[0])
              @past.shift
            end
          end
        end
      end
  
      #Move the ball according to its velocity
      def update args
  
          if isLeader
            wallBounds args
            @x += @velocity.x
            @y += @velocity.y
            @past.append({x: @x, y: @y, velocity: @velocity})
            #puts @past
  
            if (@past.length >= BALL_DISTANCE)
              if (@child != nil)
                @child.receiveNext(@past[0])
                @past.shift
              end
            end
  
          else
            puts "unexpected"
            raise "unexpected"
          end
      end
  
      def wallBounds args
          b= false
          if @x < @left_wall
            @velocity.x = @velocity.x.abs() * 1
            b=true
          elsif @x + @width > @right_wall
            @velocity.x = @velocity.x.abs() * -1
            b=true
          end
          if @y < 0
            @velocity.y = @velocity.y.abs() * 1
            b=true
          elsif @y + @height > args.grid.h
            @velocity.y = @velocity.y.abs() * -1
            b=true
          end
          mag = (@velocity.x**2.0 + @velocity.y**2.0)**0.5
          if (b == true && mag < MAX_VELOCITY)
            @velocity.x*=1.1;
            @velocity.y*=1.1;
          end
  
      end
  
      #render the ball to the screen
      def draw args
  
          #update args
          #args.outputs.solids << [@x, @y, @width, @height, 255, 255, 0];
          #args.outputs.sprits << {
            #x: @x,
            #y: @y,
            #w: @width,
            #h: @height,
            #path: "sprites/ball10.png"
          #}
          #args.outputs.sprites <<[@x, @y, @width, @height, "sprites/ball10.png"]
          args.outputs.sprites << {x: @x, y: @y, w: @width, h: @height, path:"sprites/ball10.png" }
      end
  
      def getDraw args
        #wallBounds args
        #update args
        #args.outputs.labels << [@x, @y, @number.to_s + "|" + @leastChain.to_s]
        return [@x, @y, @width, @height, "sprites/ball10.png"]
      end
  
      def getPoints args
        points = [
          {x:@x+@width/2, y: @y},
          {x:@x+@width, y:@y+@height/2},
          {x:@x+@width/2,y:@y+@height},
          {x:@x,y:@y+@height/2}
        ]
        #psize = 5.0
        #for p in points
          #args.outputs.solids << [p.x-psize/2.0, p.y-psize/2.0, psize, psize, 0, 0, 0];
        #end
        return points
      end
  
      def serialize
        {x: @x, y:@y}
      end
  
      def inspect
        serialize.to_s
      end
  
      def to_s
        serialize.to_s
      end
    end

#+end_src

*** Physics And Collisions - Arbitrary Collision - blocks.rb
#+begin_src ruby
  # ./samples/04_physics_and_collisions/09_arbitrary_collision/app/blocks.rb
  MAX_COUNT=100
  
  def universalUpdateOne args, shape
    didHit = false
    hitters = []
    #puts shape.to_s
    toCollide = nil
    for b in args.state.balls
      if [b.x, b.y, b.width, b.height].intersect_rect?(shape.bold)
        didSquare = false
        for s in shape.squareColliders
          if (s.collision?(args, b))
            didSquare = true
            didHit = true
            #s.collide(args, b)
            toCollide = s
            #hitter = b
            hitters.append(b)
          end #end if
        end #end for
        if (didSquare == false)
          for c in shape.colliders
            #puts args.state.ball.velocity
            if c.collision?(args, b.getPoints(args),b)
              #c.collide args, b
              toCollide = c
              didHit = true
              hitters.append(b)
            end #end if
          end #end for
        end #end if
      end#end if
    end#end for
    if (didHit)
      shape.count=0
      hitters = hitters.uniq
      for hitter in hitters
        hitter.makeLeader args
        #toCollide.collide(args, hitter)
        if shape.home == "squares"
          args.state.squares.delete(shape)
        elsif shape.home == "tshapes"
          args.state.tshapes.delete(shape)
        else shape.home == "lines"
          args.state.lines.delete(shape)
        end
      end
  
      #puts "HIT!" + hitter.number
    end
  end
  
  def universalUpdate args, shape
    #puts shape.home
    if (shape.count <= 1)
      universalUpdateOne args, shape
      return
    end
  
    didHit = false
    hitter = nil
    for b in args.state.ballParents
      if [b.x, b.y, b.width, b.height].intersect_rect?(shape.bold)
        didSquare = false
        for s in shape.squareColliders
          if (s.collision?(args, b))
            didSquare = true
            didHit = true
            s.collide(args, b)
            hitter = b
          end
        end
        if (didSquare == false)
          for c in shape.colliders
            #puts args.state.ball.velocity
            if c.collision?(args, b.getPoints(args),b)
              c.collide args, b
              didHit = true
              hitter = b
            end
          end
        end
      end
    end
    if (didHit)
      shape.count=shape.count-1
      shape.damageCount.append([(hitter.leastChain+1 - hitter.number)-1, args.state.tick_count])
  
    end
    i=0
    while i < shape.damageCount.length
      if shape.damageCount[i][0] <= 0
        shape.damageCount.delete_at(i)
        i-=1
      elsif shape.damageCount[i][1].elapsed_time > BALL_DISTANCE and shape.damageCount[i][0] > 1
        shape.count-=1
        shape.damageCount[i][0]-=1
        shape.damageCount[i][1] = args.state.tick_count
      end
      i+=1
    end
  end
  
  
  class Square
     attr_accessor :count, :x, :y, :home, :bold, :squareColliders, :colliders, :damageCount
     def initialize(args, x, y, block_size, orientation, block_offset)
          @x = x * block_size
          @y = y * block_size
          @block_size = block_size
          @block_offset = block_offset
          @orientation = orientation
          @damageCount = []
          @home = 'squares'
  
  
          Kernel.srand()
          @r = rand(255)
          @g = rand(255)
          @b = rand(255)
  
          @count = rand(MAX_COUNT)+1
  
          x_offset = (args.state.board_width + args.grid.w / 8) + @block_offset / 2
          @x_adjusted = @x + x_offset
          @y_adjusted = @y
          @size_adjusted = @block_size * 2 - @block_offset
  
          hypotenuse=args.state.ball_hypotenuse
          @bold = [(@x_adjusted-hypotenuse/2)-1, (@y_adjusted-hypotenuse/2)-1, @size_adjusted + hypotenuse + 2, @size_adjusted + hypotenuse + 2]
  
          @points = [
            {x:@x_adjusted, y:@y_adjusted},
            {x:@x_adjusted+@size_adjusted, y:@y_adjusted},
            {x:@x_adjusted+@size_adjusted, y:@y_adjusted+@size_adjusted},
            {x:@x_adjusted, y:@y_adjusted+@size_adjusted}
          ]
          @squareColliders = [
            SquareCollider.new(@points[0].x,@points[0].y,{x:-1,y:-1}),
            SquareCollider.new(@points[1].x-COLLISIONWIDTH,@points[1].y,{x:1,y:-1}),
            SquareCollider.new(@points[2].x-COLLISIONWIDTH,@points[2].y-COLLISIONWIDTH,{x:1,y:1}),
            SquareCollider.new(@points[3].x,@points[3].y-COLLISIONWIDTH,{x:-1,y:1}),
          ]
          @colliders = [
            LinearCollider.new(@points[0],@points[1], :neg),
            LinearCollider.new(@points[1],@points[2], :neg),
            LinearCollider.new(@points[2],@points[3], :pos),
            LinearCollider.new(@points[0],@points[3], :pos)
          ]
     end
  
     def draw(args)
      #Offset the coordinates to the edge of the game area
      x_offset = (args.state.board_width + args.grid.w / 8) + @block_offset / 2
      #args.outputs.solids << [@x + x_offset, @y, @block_size * 2 - @block_offset, @block_size * 2 - @block_offset, @r, @g, @b]
      args.outputs.solids <<{x: (@x + x_offset), y: (@y), w: (@block_size * 2 - @block_offset), h: (@block_size * 2 - @block_offset), r: @r , g: @g , b: @b }
      #args.outputs.solids << @bold.append([255,0,0])
      args.outputs.labels << [@x + x_offset + (@block_size * 2 - @block_offset)/2, (@y) + (@block_size * 2 - @block_offset)/2, @count.to_s]
  
     end
  
     def update args
       universalUpdate args, self
     end
  end
  
  class TShape
      attr_accessor :count, :x, :y, :home, :bold, :squareColliders, :colliders, :damageCount
      def initialize(args, x, y, block_size, orientation, block_offset)
          @x = x * block_size
          @y = y * block_size
          @block_size = block_size
          @block_offset = block_offset
          @orientation = orientation
          @damageCount = []
          @home = "tshapes"
  
          Kernel.srand()
          @r = rand(255)
          @g = rand(255)
          @b = rand(255)
  
          @count = rand(MAX_COUNT)+1
  
  
          @shapePoints = getShapePoints(args)
          minX={x:INFINITY, y:0}
          minY={x:0, y:INFINITY}
          maxX={x:-INFINITY, y:0}
          maxY={x:0, y:-INFINITY}
          for p in @shapePoints
            if p.x < minX.x
              minX = p
            end
            if p.x > maxX.x
              maxX = p
            end
            if p.y < minY.y
              minY = p
            end
            if p.y > maxY.y
              maxY = p
            end
          end
  
  
          hypotenuse=args.state.ball_hypotenuse
  
          @bold = [(minX.x-hypotenuse/2)-1, (minY.y-hypotenuse/2)-1, -((minX.x-hypotenuse/2)-1)+(maxX.x + hypotenuse + 2), -((minY.y-hypotenuse/2)-1)+(maxY.y + hypotenuse + 2)]
      end
      def getShapePoints(args)
        points=[]
        x_offset = (args.state.board_width + args.grid.w / 8) + (@block_offset / 2)
  
        if @orientation == :right
            #args.outputs.solids << [@x + x_offset, @y, @block_size - @block_offset, @block_size * 3 - @block_offset, @r, @g, @b]
            #args.outputs.solids << [@x + x_offset, @y + @block_size, @block_size * 2, @block_size, @r, @g, @b]
            points = [
              {x:@x + x_offset, y:@y},
              {x:(@x + x_offset)+(@block_size - @block_offset), y:@y},
              {x:(@x + x_offset)+(@block_size - @block_offset),y:@y + @block_size},
              {x:(@x + x_offset)+ @block_size * 2,y:@y + @block_size},
              {x:(@x + x_offset)+ @block_size * 2,y:@y + @block_size+@block_size},
              {x:(@x + x_offset)+(@block_size - @block_offset),y:@y + @block_size+@block_size},
              {x:(@x + x_offset)+(@block_size - @block_offset), y:@y+ @block_size * 3 - @block_offset},
              {x:@x + x_offset , y:@y+ @block_size * 3 - @block_offset}
            ]
            @squareColliders = [
              SquareCollider.new(points[0].x,points[0].y,{x:-1,y:-1}),
              SquareCollider.new(points[1].x-COLLISIONWIDTH,points[1].y,{x:1,y:-1}),
              SquareCollider.new(points[2].x,points[2].y-COLLISIONWIDTH,{x:1,y:-1}),
              SquareCollider.new(points[3].x-COLLISIONWIDTH,points[3].y,{x:1,y:-1}),
              SquareCollider.new(points[4].x-COLLISIONWIDTH,points[4].y-COLLISIONWIDTH,{x:1,y:1}),
              SquareCollider.new(points[5].x,points[5].y,{x:1,y:1}),
              SquareCollider.new(points[6].x-COLLISIONWIDTH,points[6].y-COLLISIONWIDTH,{x:1,y:1}),
              SquareCollider.new(points[7].x,points[7].y-COLLISIONWIDTH,{x:-1,y:1}),
            ]
            @colliders = [
              LinearCollider.new(points[0],points[1], :neg),
              LinearCollider.new(points[1],points[2], :neg),
              LinearCollider.new(points[2],points[3], :neg),
              LinearCollider.new(points[3],points[4], :neg),
              LinearCollider.new(points[4],points[5], :pos),
              LinearCollider.new(points[5],points[6], :neg),
              LinearCollider.new(points[6],points[7], :pos),
              LinearCollider.new(points[0],points[7], :pos)
            ]
        elsif @orientation == :up
            #args.outputs.solids << [@x + x_offset, @y, @block_size * 3 - @block_offset, @block_size - @block_offset, @r, @g, @b]
            #args.outputs.solids << [@x + x_offset + @block_size, @y, @block_size, @block_size * 2, @r, @g, @b]
            points = [
              {x:@x + x_offset, y:@y},
              {x:(@x + x_offset)+(@block_size * 3 - @block_offset), y:@y},
              {x:(@x + x_offset)+(@block_size * 3 - @block_offset), y:@y+(@block_size - @block_offset)},
              {x:@x + x_offset + @block_size + @block_size, y:@y+(@block_size - @block_offset)},
              {x:@x + x_offset + @block_size + @block_size, y:@y+@block_size*2},
              {x:@x + x_offset + @block_size, y:@y+@block_size*2},
              {x:@x + x_offset + @block_size, y:@y+(@block_size - @block_offset)},
              {x:@x + x_offset, y:@y+(@block_size - @block_offset)}
            ]
            @squareColliders = [
              SquareCollider.new(points[0].x,points[0].y,{x:-1,y:-1}),
              SquareCollider.new(points[1].x-COLLISIONWIDTH,points[1].y,{x:1,y:-1}),
              SquareCollider.new(points[2].x-COLLISIONWIDTH,points[2].y-COLLISIONWIDTH,{x:1,y:1}),
              SquareCollider.new(points[3].x,points[3].y,{x:1,y:1}),
              SquareCollider.new(points[4].x-COLLISIONWIDTH,points[4].y-COLLISIONWIDTH,{x:1,y:1}),
              SquareCollider.new(points[5].x,points[5].y-COLLISIONWIDTH,{x:-1,y:1}),
              SquareCollider.new(points[6].x-COLLISIONWIDTH,points[6].y,{x:-1,y:1}),
              SquareCollider.new(points[7].x,points[7].y-COLLISIONWIDTH,{x:-1,y:1}),
            ]
            @colliders = [
              LinearCollider.new(points[0],points[1], :neg),
              LinearCollider.new(points[1],points[2], :neg),
              LinearCollider.new(points[2],points[3], :pos),
              LinearCollider.new(points[3],points[4], :neg),
              LinearCollider.new(points[4],points[5], :pos),
              LinearCollider.new(points[5],points[6], :neg),
              LinearCollider.new(points[6],points[7], :pos),
              LinearCollider.new(points[0],points[7], :pos)
            ]
        elsif @orientation == :left
            #args.outputs.solids << [@x + x_offset + @block_size, @y, @block_size - @block_offset, @block_size * 3 - @block_offset, @r, @g, @b]
            #args.outputs.solids << [@x + x_offset, @y + @block_size, @block_size * 2 - @block_offset, @block_size - @block_offset, @r, @g, @b]
            xh = @x + x_offset
            #points = [
              #{x:@x + x_offset, y:@y},
              #{x:(@x + x_offset)+(@block_size - @block_offset), y:@y},
              #{x:(@x + x_offset)+(@block_size - @block_offset),y:@y + @block_size},
              #{x:(@x + x_offset)+ @block_size * 2,y:@y + @block_size},
              #{x:(@x + x_offset)+ @block_size * 2,y:@y + @block_size+@block_size},
              #{x:(@x + x_offset)+(@block_size - @block_offset),y:@y + @block_size+@block_size},
              #{x:(@x + x_offset)+(@block_size - @block_offset), y:@y+ @block_size * 3 - @block_offset},
              #{x:@x + x_offset , y:@y+ @block_size * 3 - @block_offset}
            #]
            points = [
              {x:@x + x_offset + @block_size, y:@y},
              {x:@x + x_offset + @block_size + (@block_size - @block_offset), y:@y},
              {x:@x + x_offset + @block_size + (@block_size - @block_offset),y:@y+@block_size*3- @block_offset},
              {x:@x + x_offset + @block_size, y:@y+@block_size*3- @block_offset},
              {x:@x + x_offset+@block_size, y:@y+@block_size*2- @block_offset},
              {x:@x + x_offset, y:@y+@block_size*2- @block_offset},
              {x:@x + x_offset, y:@y+@block_size},
              {x:@x + x_offset+@block_size, y:@y+@block_size}
            ]
            @squareColliders = [
              SquareCollider.new(points[0].x,points[0].y,{x:-1,y:-1}),
              SquareCollider.new(points[1].x-COLLISIONWIDTH,points[1].y,{x:1,y:-1}),
              SquareCollider.new(points[2].x-COLLISIONWIDTH,points[2].y-COLLISIONWIDTH,{x:1,y:1}),
              SquareCollider.new(points[3].x,points[3].y-COLLISIONWIDTH,{x:-1,y:1}),
              SquareCollider.new(points[4].x-COLLISIONWIDTH,points[4].y,{x:-1,y:1}),
              SquareCollider.new(points[5].x,points[5].y-COLLISIONWIDTH,{x:-1,y:1}),
              SquareCollider.new(points[6].x,points[6].y,{x:-1,y:-1}),
              SquareCollider.new(points[7].x-COLLISIONWIDTH,points[7].y-COLLISIONWIDTH,{x:-1,y:-1}),
            ]
            @colliders = [
              LinearCollider.new(points[0],points[1], :neg),
              LinearCollider.new(points[1],points[2], :neg),
              LinearCollider.new(points[2],points[3], :pos),
              LinearCollider.new(points[3],points[4], :neg),
              LinearCollider.new(points[4],points[5], :pos),
              LinearCollider.new(points[5],points[6], :neg),
              LinearCollider.new(points[6],points[7], :neg),
              LinearCollider.new(points[0],points[7], :pos)
            ]
        elsif @orientation == :down
            #args.outputs.solids << [@x + x_offset, @y + @block_size, @block_size * 3 - @block_offset, @block_size - @block_offset, @r, @g, @b]
            #args.outputs.solids << [@x + x_offset + @block_size, @y, @block_size - @block_offset, @block_size * 2 - @block_offset, @r, @g, @b]
  
            points = [
              {x:@x + x_offset, y:@y+(@block_size*2)-@block_offset},
              {x:@x + x_offset+ @block_size*3-@block_offset, y:@y+(@block_size*2)-@block_offset},
              {x:@x + x_offset+ @block_size*3-@block_offset, y:@y+(@block_size)},
              {x:@x + x_offset+ @block_size*2-@block_offset, y:@y+(@block_size)},
              {x:@x + x_offset+ @block_size*2-@block_offset, y:@y},#
              {x:@x + x_offset+ @block_size, y:@y},#
              {x:@x + x_offset + @block_size, y:@y+(@block_size)},
              {x:@x + x_offset, y:@y+(@block_size)}
            ]
            @squareColliders = [
              SquareCollider.new(points[0].x,points[0].y-COLLISIONWIDTH,{x:-1,y:1}),
              SquareCollider.new(points[1].x-COLLISIONWIDTH,points[1].y-COLLISIONWIDTH,{x:1,y:1}),
              SquareCollider.new(points[2].x-COLLISIONWIDTH,points[2].y,{x:1,y:-1}),
              SquareCollider.new(points[3].x,points[3].y-COLLISIONWIDTH,{x:1,y:-1}),
              SquareCollider.new(points[4].x-COLLISIONWIDTH,points[4].y,{x:1,y:-1}),
              SquareCollider.new(points[5].x,points[5].y,{x:-1,y:-1}),
              SquareCollider.new(points[6].x-COLLISIONWIDTH,points[6].y-COLLISIONWIDTH,{x:-1,y:-1}),
              SquareCollider.new(points[7].x,points[7].y,{x:-1,y:-1}),
            ]
            @colliders = [
              LinearCollider.new(points[0],points[1], :pos),
              LinearCollider.new(points[1],points[2], :pos),
              LinearCollider.new(points[2],points[3], :neg),
              LinearCollider.new(points[3],points[4], :pos),
              LinearCollider.new(points[4],points[5], :neg),
              LinearCollider.new(points[5],points[6], :pos),
              LinearCollider.new(points[6],points[7], :neg),
              LinearCollider.new(points[0],points[7], :neg)
            ]
        end
        return points
      end
  
      def draw(args)
          #Offset the coordinates to the edge of the game area
          x_offset = (args.state.board_width + args.grid.w / 8) + (@block_offset / 2)
  
          if @orientation == :right
              #args.outputs.solids << [@x + x_offset, @y, @block_size - @block_offset, @block_size * 3 - @block_offset, @r, @g, @b]
              args.outputs.solids << {x: (@x + x_offset), y: @y, w: @block_size - @block_offset, h: (@block_size * 3 - @block_offset), r: @r , g: @g, b: @b}
              #args.outputs.solids << [@x + x_offset, @y + @block_size, @block_size * 2, @block_size, @r, @g, @b]
              args.outputs.solids << {x: (@x + x_offset), y: (@y + @block_size), w: (@block_size * 2), h: (@block_size), r: @r , g: @g, b: @b }
          elsif @orientation == :up
              #args.outputs.solids << [@x + x_offset, @y, @block_size * 3 - @block_offset, @block_size - @block_offset, @r, @g, @b]
              args.outputs.solids << {x: (@x + x_offset), y: (@y), w: (@block_size * 3 - @block_offset), h: (@block_size - @block_offset), r: @r , g: @g, b: @b}
              #args.outputs.solids << [@x + x_offset + @block_size, @y, @block_size, @block_size * 2, @r, @g, @b]
              args.outputs.solids << {x: (@x + x_offset + @block_size), y: (@y), w: (@block_size), h: (@block_size * 2), r: @r , g: @g, b: @b}
          elsif @orientation == :left
              #args.outputs.solids << [@x + x_offset + @block_size, @y, @block_size - @block_offset, @block_size * 3 - @block_offset, @r, @g, @b]
              args.outputs.solids << {x: (@x + x_offset + @block_size), y: (@y), w: (@block_size - @block_offset), h: (@block_size * 3 - @block_offset), r: @r , g: @g, b: @b}
              #args.outputs.solids << [@x + x_offset, @y + @block_size, @block_size * 2 - @block_offset, @block_size - @block_offset, @r, @g, @b]
              args.outputs.solids << {x: (@x + x_offset), y: (@y + @block_size), w: (@block_size * 2 - @block_offset), h: (@block_size - @block_offset), r: @r , g: @g, b: @b}
          elsif @orientation == :down
              #args.outputs.solids << [@x + x_offset, @y + @block_size, @block_size * 3 - @block_offset, @block_size - @block_offset, @r, @g, @b]
              args.outputs.solids << {x: (@x + x_offset), y: (@y + @block_size), w: (@block_size * 3 - @block_offset), h: (@block_size - @block_offset), r: @r , g: @g, b: @b}
              #args.outputs.solids << [@x + x_offset + @block_size, @y, @block_size - @block_offset, @block_size * 2 - @block_offset, @r, @g, @b]
              args.outputs.solids << {x: (@x + x_offset + @block_size), y: (@y), w: (@block_size - @block_offset), h: ( @block_size * 2 - @block_offset), r: @r , g: @g, b: @b}
          end
  
          #psize = 5.0
          #for p in @shapePoints
            #args.outputs.solids << [p.x-psize/2, p.y-psize/2, psize, psize, 0, 0, 0]
          #end
          args.outputs.labels << [@x + x_offset + (@block_size * 2 - @block_offset)/2, (@y) + (@block_size * 2 - @block_offset)/2, @count.to_s]
  
      end
  
      def updateOne_old args
        didHit = false
        hitter = nil
        toCollide = nil
        for b in args.state.balls
          if [b.x, b.y, b.width, b.height].intersect_rect?(@bold)
            didSquare = false
            for s in @squareColliders
              if (s.collision?(args, b))
                didSquare = true
                didHit = true
                #s.collide(args, b)
                toCollide = s
                hitter = b
                break
              end
            end
            if (didSquare == false)
              for c in @colliders
                #puts args.state.ball.velocity
                if c.collision?(args, b.getPoints(args),b)
                  #c.collide args, b
                  toCollide = c
                  didHit = true
                  hitter = b
                  break
                end
              end
            end
          end
          if didHit
            break
          end
        end
        if (didHit)
          @count=0
          hitter.makeLeader args
          #toCollide.collide(args, hitter)
          args.state.tshapes.delete(self)
          #puts "HIT!" + hitter.number
        end
      end
  
      def update_old args
        if (@count == 1)
          updateOne args
          return
        end
        didHit = false
        hitter = nil
        for b in args.state.ballParents
          if [b.x, b.y, b.width, b.height].intersect_rect?(@bold)
            didSquare = false
            for s in @squareColliders
              if (s.collision?(args, b))
                didSquare = true
                didHit=true
                s.collide(args, b)
                hitter = b
              end
            end
            if (didSquare == false)
              for c in @colliders
                #puts args.state.ball.velocity
                if c.collision?(args, b.getPoints(args), b)
                  c.collide args, b
                  didHit=true
                  hitter = b
                end
              end
            end
          end
        end
        if (didHit)
          @count=@count-1
          @damageCount.append([(hitter.leastChain+1 - hitter.number)-1, args.state.tick_count])
  
          if (@count == 0)
            args.state.tshapes.delete(self)
            return
          end
        end
        i=0
  
        while i < @damageCount.length
          if @damageCount[i][0] <= 0
            @damageCount.delete_at(i)
            i-=1
          elsif @damageCount[i][1].elapsed_time > BALL_DISTANCE
            @count-=1
            @damageCount[i][0]-=1
          end
          if (@count == 0)
            args.state.tshapes.delete(self)
            return
          end
          i+=1
        end
      end #end update
  
      def update args
        universalUpdate args, self
      end
  
  end
  
  class Line
      attr_accessor :count, :x, :y, :home, :bold, :squareColliders, :colliders, :damageCount
      def initialize(args, x, y, block_size, orientation, block_offset)
          @x = x * block_size
          @y = y * block_size
          @block_size = block_size
          @block_offset = block_offset
          @orientation = orientation
          @damageCount = []
          @home = "lines"
  
          Kernel.srand()
          @r = rand(255)
          @g = rand(255)
          @b = rand(255)
  
          @count = rand(MAX_COUNT)+1
  
          @shapePoints = getShapePoints(args)
          minX={x:INFINITY, y:0}
          minY={x:0, y:INFINITY}
          maxX={x:-INFINITY, y:0}
          maxY={x:0, y:-INFINITY}
          for p in @shapePoints
            if p.x < minX.x
              minX = p
            end
            if p.x > maxX.x
              maxX = p
            end
            if p.y < minY.y
              minY = p
            end
            if p.y > maxY.y
              maxY = p
            end
          end
  
  
          hypotenuse=args.state.ball_hypotenuse
  
          @bold = [(minX.x-hypotenuse/2)-1, (minY.y-hypotenuse/2)-1, -((minX.x-hypotenuse/2)-1)+(maxX.x + hypotenuse + 2), -((minY.y-hypotenuse/2)-1)+(maxY.y + hypotenuse + 2)]
      end
  
      def getShapePoints(args)
        points=[]
        x_offset = (args.state.board_width + args.grid.w / 8) + (@block_offset / 2)
  
        if @orientation == :right
          #args.outputs.solids << [@x + x_offset, @y, @block_size * 3 - @block_offset, @block_size - @block_offset, @r, @g, @b]
          xa =@x + x_offset
          ya =@y
          wa =@block_size * 3 - @block_offset
          ha =(@block_size - @block_offset)
        elsif @orientation == :up
          #args.outputs.solids << [@x + x_offset, @y, @block_size - @block_offset, @block_size * 3 - @block_offset, @r, @g, @b]
          xa =@x + x_offset
          ya =@y
          wa =@block_size - @block_offset
          ha =@block_size * 3 - @block_offset
  
        elsif @orientation == :left
          #args.outputs.solids << [@x + x_offset, @y, @block_size * 3 - @block_offset, @block_size - @block_offset, @r, @g, @b]
          xa =@x + x_offset
          ya =@y
          wa =@block_size * 3 - @block_offset
          ha =@block_size - @block_offset
        elsif @orientation == :down
          #args.outputs.solids << [@x + x_offset, @y, @block_size - @block_offset, @block_size * 3 - @block_offset, @r, @g, @b]
          xa =@x + x_offset
          ya =@y
          wa =@block_size - @block_offset
          ha =@block_size * 3 - @block_offset
        end
        points = [
          {x: xa, y:ya},
          {x: xa + wa,y:ya},
          {x: xa + wa,y:ya+ha},
          {x: xa, y:ya+ha},
        ]
        @squareColliders = [
          SquareCollider.new(points[0].x,points[0].y,{x:-1,y:-1}),
          SquareCollider.new(points[1].x-COLLISIONWIDTH,points[1].y,{x:1,y:-1}),
          SquareCollider.new(points[2].x-COLLISIONWIDTH,points[2].y-COLLISIONWIDTH,{x:1,y:1}),
          SquareCollider.new(points[3].x,points[3].y-COLLISIONWIDTH,{x:-1,y:1}),
        ]
        @colliders = [
          LinearCollider.new(points[0],points[1], :neg),
          LinearCollider.new(points[1],points[2], :neg),
          LinearCollider.new(points[2],points[3], :pos),
          LinearCollider.new(points[0],points[3], :pos),
        ]
        return points
      end
  
      def update args
        universalUpdate args, self
      end
  
      def draw(args)
          x_offset = (args.state.board_width + args.grid.w / 8) + @block_offset / 2
  
          if @orientation == :right
              args.outputs.solids << [@x + x_offset, @y, @block_size * 3 - @block_offset, @block_size - @block_offset, @r, @g, @b]
          elsif @orientation == :up
              args.outputs.solids << [@x + x_offset, @y, @block_size - @block_offset, @block_size * 3 - @block_offset, @r, @g, @b]
          elsif @orientation == :left
              args.outputs.solids << [@x + x_offset, @y, @block_size * 3 - @block_offset, @block_size - @block_offset, @r, @g, @b]
          elsif @orientation == :down
              args.outputs.solids << [@x + x_offset, @y, @block_size - @block_offset, @block_size * 3 - @block_offset, @r, @g, @b]
          end
  
          args.outputs.labels << [@x + x_offset + (@block_size * 2 - @block_offset)/2, (@y) + (@block_size * 2 - @block_offset)/2, @count.to_s]
  
      end
  end

#+end_src

*** Physics And Collisions - Arbitrary Collision - linear_collider.rb
#+begin_src ruby
  # ./samples/04_physics_and_collisions/09_arbitrary_collision/app/linear_collider.rb
  
  COLLISIONWIDTH=8
  
  class LinearCollider
    attr_reader :pointA, :pointB
    def initialize (pointA, pointB, mode,collisionWidth=COLLISIONWIDTH)
      @pointA = pointA
      @pointB = pointB
      @mode = mode
      @collisionWidth = collisionWidth
  
      if (@pointA.x > @pointB.x)
        @pointA, @pointB = @pointB, @pointA
      end
  
      @linearCollider_collision_once = false
    end
  
    def collisionSlope args
      if (@pointB.x-@pointA.x == 0)
        return INFINITY
      end
      return (@pointB.y - @pointA.y) / (@pointB.x - @pointA.x)
    end
  
  
    def collision? (args, points, ball=nil)
  
      slope = collisionSlope args
      result = false
  
      # calculate a vector with a magnitude of (1/2)collisionWidth and a direction perpendicular to the collision line
      vect=nil;mag=nil;vect=nil;
      if @mode == :both
        vect = {x: @pointB.x - @pointA.x, y:@pointB.y - @pointA.y}
        mag  = (vect.x**2 + vect.y**2)**0.5
        vect = {y: -1*(vect.x/(mag))*@collisionWidth*0.5, x: (vect.y/(mag))*@collisionWidth*0.5}
      else
        vect = {x: @pointB.x - @pointA.x, y:@pointB.y - @pointA.y}
        mag  = (vect.x**2 + vect.y**2)**0.5
        vect = {y: -1*(vect.x/(mag))*@collisionWidth, x: (vect.y/(mag))*@collisionWidth}
      end
  
      rpointA=nil;rpointB=nil;rpointC=nil;rpointD=nil;
      if @mode == :pos
        rpointA = {x:@pointA.x + vect.x, y:@pointA.y + vect.y}
        rpointB = {x:@pointB.x + vect.x, y:@pointB.y + vect.y}
        rpointC = {x:@pointB.x, y:@pointB.y}
        rpointD = {x:@pointA.x, y:@pointA.y}
      elsif @mode == :neg
        rpointA = {x:@pointA.x, y:@pointA.y}
        rpointB = {x:@pointB.x, y:@pointB.y}
        rpointC = {x:@pointB.x - vect.x, y:@pointB.y - vect.y}
        rpointD = {x:@pointA.x - vect.x, y:@pointA.y - vect.y}
      elsif @mode == :both
        rpointA = {x:@pointA.x + vect.x, y:@pointA.y + vect.y}
        rpointB = {x:@pointB.x + vect.x, y:@pointB.y + vect.y}
        rpointC = {x:@pointB.x - vect.x, y:@pointB.y - vect.y}
        rpointD = {x:@pointA.x - vect.x, y:@pointA.y - vect.y}
      end
      #four point rectangle
  
  
  
      if ball != nil
        xs = [rpointA.x,rpointB.x,rpointC.x,rpointD.x]
        ys = [rpointA.y,rpointB.y,rpointC.y,rpointD.y]
        correct = 1
        rect1 = [ball.x, ball.y, ball.width, ball.height]
        #$r1 = rect1
        rect2 = [xs.min-correct,ys.min-correct,(xs.max-xs.min)+correct*2,(ys.max-ys.min)+correct*2]
        #$r2 = rect2
        if rect1.intersect_rect?(rect2) == false
          return false
        end
      end
  
  
      #area of a triangle
      triArea = -> (a,b,c) { ((a.x * (b.y - c.y) + b.x * (c.y - a.y) + c.x * (a.y - b.y))/2.0).abs }
  
      #if at least on point is in the rectangle then collision? is true - otherwise false
      for point in points
        #Check whether a given point lies inside a rectangle or not:
        #if the sum of the area of traingls, PAB, PBC, PCD, PAD equal the area of the rec, then an intersection has occured
        areaRec =  triArea.call(rpointA, rpointB, rpointC)+triArea.call(rpointA, rpointC, rpointD)
        areaSum = [
          triArea.call(point, rpointA, rpointB),triArea.call(point, rpointB, rpointC),
          triArea.call(point, rpointC, rpointD),triArea.call(point, rpointA, rpointD)
        ].inject(0){|sum,x| sum + x }
        e = 0.0001 #allow for minor error
        if areaRec>= areaSum-e and areaRec<= areaSum+e
          result = true
          #return true
          break
        end
      end
  
      #args.outputs.lines << [@pointA.x, @pointA.y, @pointB.x, @pointB.y,     000, 000, 000]
      #args.outputs.lines << [rpointA.x, rpointA.y, rpointB.x, rpointB.y,     255, 000, 000]
      #args.outputs.lines << [rpointC.x, rpointC.y, rpointD.x, rpointD.y,     000, 000, 255]
  
  
      #puts (rpointA.x.to_s + " " +  rpointA.y.to_s + " " + rpointB.x.to_s + " "+ rpointB.y.to_s)
      return result
    end #end collision?
  
    def getRepelMagnitude (fbx, fby, vrx, vry, ballMag)
      a = fbx ; b = vrx ; c = fby
      d = vry ; e = ballMag
      if b**2 + d**2 == 0
        #unexpected
      end
      x1 = (-a*b+-c*d + (e**2 * b**2 - b**2 * c**2 + 2*a*b*c*d + e**2 + d**2 - a**2 * d**2)**0.5)/(b**2 + d**2)
      x2 = -((a*b + c*d + (e**2 * b**2 - b**2 * c**2 + 2*a*b*c*d + e**2 * d**2 - a**2 * d**2)**0.5)/(b**2 + d**2))
      err = 0.00001
      o = ((fbx + x1*vrx)**2 + (fby + x1*vry)**2 ) ** 0.5
      p = ((fbx + x2*vrx)**2 + (fby + x2*vry)**2 ) ** 0.5
      r = 0
      if (ballMag >= o-err and ballMag <= o+err)
        r = x1
      elsif (ballMag >= p-err and ballMag <= p+err)
        r = x2
      else
        #unexpected
      end
      return r
    end
  
    def collide args, ball
      slope = collisionSlope args
  
      # perpVect: normal vector perpendicular to collision
      perpVect = {x: @pointB.x - @pointA.x, y:@pointB.y - @pointA.y}
      mag  = (perpVect.x**2 + perpVect.y**2)**0.5
      perpVect = {x: perpVect.x/(mag), y: perpVect.y/(mag)}
      perpVect = {x: -perpVect.y, y: perpVect.x}
      if perpVect.y > 0 #ensure perpVect points upward
        perpVect = {x: perpVect.x*-1, y: perpVect.y*-1}
      end
      previousPosition = {
        x:ball.x-ball.velocity.x,
        y:ball.y-ball.velocity.y
      }
      yInterc = @pointA.y + -slope*@pointA.x
      if slope == INFINITY
        if previousPosition.x < @pointA.x
          perpVect = {x: perpVect.x*-1, y: perpVect.y*-1}
          yInterc = -INFINITY
        end
      elsif previousPosition.y < slope*previousPosition.x + yInterc #check if ball is bellow or above the collider to determine if perpVect is - or +
        perpVect = {x: perpVect.x*-1, y: perpVect.y*-1}
      end
  
      velocityMag = (ball.velocity.x**2 + ball.velocity.y**2)**0.5
      theta_ball=Math.atan2(ball.velocity.y,ball.velocity.x) #the angle of the ball's velocity
      theta_repel=Math.atan2(perpVect.y,perpVect.x) #the angle of the repelling force(perpVect)
  
      fbx = velocityMag * Math.cos(theta_ball) #the x component of the ball's velocity
      fby = velocityMag * Math.sin(theta_ball) #the y component of the ball's velocity
  
      #the magnitude of the repelling force
      repelMag = getRepelMagnitude(fbx, fby, perpVect.x, perpVect.y, (ball.velocity.x**2 + ball.velocity.y**2)**0.5)
      frx = repelMag* Math.cos(theta_repel) #the x component of the repel's velocity | magnitude is set to twice of fbx
      fry = repelMag* Math.sin(theta_repel) #the y component of the repel's velocity | magnitude is set to twice of fby
  
      fsumx = fbx+frx #sum of x forces
      fsumy = fby+fry #sum of y forces
      fr = velocityMag#fr is the resulting magnitude
      thetaNew = Math.atan2(fsumy, fsumx)  #thetaNew is the resulting angle
      xnew = fr*Math.cos(thetaNew)#resulting x velocity
      ynew = fr*Math.sin(thetaNew)#resulting y velocity
      if (velocityMag < MAX_VELOCITY)
        ball.velocity =  Vector2d.new(xnew*1.1, ynew*1.1)
      else
        ball.velocity =  Vector2d.new(xnew, ynew)
      end
  
    end
  end

#+end_src

*** Physics And Collisions - Arbitrary Collision - main.rb
#+begin_src ruby
  # ./samples/04_physics_and_collisions/09_arbitrary_collision/app/main.rb
  INFINITY= 10**10
  MAX_VELOCITY = 8.0
  BALL_COUNT = 90
  BALL_DISTANCE = 20
  require 'app/vector2d.rb'
  require 'app/blocks.rb'
  require 'app/ball.rb'
  require 'app/rectangle.rb'
  require 'app/linear_collider.rb'
  require 'app/square_collider.rb'
  
  
  
  #Method to init default values
  def defaults args
    args.state.board_width ||= args.grid.w / 4
    args.state.board_height ||= args.grid.h
    args.state.game_area ||= [(args.state.board_width + args.grid.w / 8), 0, args.state.board_width, args.grid.h]
    args.state.balls ||= []
    args.state.num_balls ||= 0
    args.state.ball_created_at ||= args.state.tick_count
    args.state.ball_hypotenuse = (10**2 + 10**2)**0.5
    args.state.ballParents ||=nil
  
    init_blocks args
    init_balls args
  end
  
  begin :default_methods
    def init_blocks args
      block_size = args.state.board_width / 8
      #Space inbetween each block
      block_offset = 4
  
      args.state.squares ||=[
        Square.new(args, 2, 0, block_size, :right, block_offset),
        Square.new(args, 5, 0, block_size, :right, block_offset),
        Square.new(args, 6, 7, block_size, :right, block_offset)
      ]
  
  
      #Possible orientations are :right, :left, :up, :down
  
  
      args.state.tshapes ||= [
        TShape.new(args, 0, 6, block_size, :left, block_offset),
        TShape.new(args, 3, 3, block_size, :down, block_offset),
        TShape.new(args, 0, 3, block_size, :right, block_offset),
        TShape.new(args, 0, 11, block_size, :up, block_offset)
      ]
  
      args.state.lines ||= [
        Line.new(args,3, 8, block_size, :down, block_offset),
        Line.new(args, 7, 3, block_size, :up, block_offset),
        Line.new(args, 3, 7, block_size, :right, block_offset)
      ]
  
      #exit()
    end
  
    def init_balls args
      return unless args.state.num_balls < BALL_COUNT
  
  
      #only create a new ball every 10 ticks
      return unless args.state.ball_created_at.elapsed_time > 10
  
      if (args.state.num_balls == 0)
        args.state.balls.append(Ball.new(args,args.state.num_balls,BALL_COUNT-1, nil, nil))
        args.state.ballParents = [args.state.balls[0]]
      else
        args.state.balls.append(Ball.new(args,args.state.num_balls,BALL_COUNT-1, args.state.balls.last, nil) )
        args.state.balls[-2].child = args.state.balls[-1]
      end
      args.state.ball_created_at = args.state.tick_count
      args.state.num_balls += 1
    end
  end
  
  #Render loop
  def render args
    bgClr = {r:10, g:10, b:200}
    bgClr = {r:255-30, g:255-30, b:255-30}
  
    args.outputs.solids << [0, 0, $args.grid.right, $args.grid.top, bgClr[:r], bgClr[:g], bgClr[:b]];
    args.outputs.borders << args.state.game_area
  
    render_instructions args
    render_shapes args
  
    render_balls args
  
    #args.state.rectangle.draw args
  
    args.outputs.sprites << [$args.grid.right-(args.state.board_width + args.grid.w / 8), 0, $args.grid.right, $args.grid.top, "sprites/square-white-2.png", 0, 255, bgClr[:r], bgClr[:g], bgClr[:b]]
    args.outputs.sprites << [0, 0, (args.state.board_width + args.grid.w / 8), $args.grid.top, "sprites/square-white-2.png", 0, 255, bgClr[:r], bgClr[:g], bgClr[:b]]
  
  end
  
  begin :render_methods
    def render_instructions args
      #gtk.current_framerate
      args.outputs.labels << [20, $args.grid.top-20, "FPS: " + $gtk.current_framerate.to_s]
      if (args.state.balls != nil && args.state.balls[0] != nil)
          bx =  args.state.balls[0].velocity.x
          by =  args.state.balls[0].velocity.y
          bmg = (bx**2.0 + by**2.0)**0.5
          args.outputs.labels << [20, $args.grid.top-20-20, "V: " + bmg.to_s ]
      end
  
  
    end
  
    def render_shapes args
      for s in args.state.squares
        s.draw args
      end
  
      for l in args.state.lines
        l.draw args
      end
  
      for t in args.state.tshapes
        t.draw args
      end
  
  
    end
  
    def render_balls args
      #args.state.balls.each do |ball|
        #ball.draw args
      #end
  
      args.outputs.sprites << args.state.balls.map do |ball|
        ball.getDraw args
      end
    end
  end
  
  #Calls all methods necessary for performing calculations
  def calc args
    for b in args.state.ballParents
      b.update args
    end
  
    for s in args.state.squares
      s.update args
    end
  
    for l in args.state.lines
      l.update args
    end
  
    for t in args.state.tshapes
      t.update args
    end
  
  
  
  end
  
  begin :calc_methods
  
  end
  
  def tick args
    defaults args
    render args
    calc args
  end

#+end_src

*** Physics And Collisions - Arbitrary Collision - paddle.rb
#+begin_src ruby
  # ./samples/04_physics_and_collisions/09_arbitrary_collision/app/paddle.rb
  class Paddle
    attr_accessor :enabled
  
    def initialize ()
      @x=WIDTH/2
      @y=100
      @width=100
      @height=20
      @speed=10
  
      @xyCollision  = LinearCollider.new({x: @x,y: @y+@height+5}, {x: @x+@width, y: @y+@height+5})
      @xyCollision2 = LinearCollider.new({x: @x,y: @y}, {x: @x+@width, y: @y}, :pos)
      @xyCollision3 = LinearCollider.new({x: @x,y: @y}, {x: @x, y: @y+@height+5})
      @xyCollision4 = LinearCollider.new({x: @x+@width,y: @y}, {x: @x+@width, y: @y+@height+5}, :pos)
  
      @enabled = true
    end
  
    def update args
      @xyCollision.resetPoints({x: @x,y: @y+@height+5}, {x: @x+@width, y: @y+@height+5})
      @xyCollision2.resetPoints({x: @x,y: @y}, {x: @x+@width, y: @y})
      @xyCollision3.resetPoints({x: @x,y: @y}, {x: @x, y: @y+@height+5})
      @xyCollision4.resetPoints({x: @x+@width,y: @y}, {x: @x+@width, y: @y+@height+5})
  
      @xyCollision.update  args
      @xyCollision2.update args
      @xyCollision3.update args
      @xyCollision4.update args
  
      args.inputs.keyboard.key_held.left  ||= false
      args.inputs.keyboard.key_held.right  ||= false
  
      if not (args.inputs.keyboard.key_held.left == args.inputs.keyboard.key_held.right)
        if args.inputs.keyboard.key_held.left && @enabled
          @x-=@speed
        elsif args.inputs.keyboard.key_held.right && @enabled
          @x+=@speed
        end
      end
  
      xmin =WIDTH/4
      xmax = 3*(WIDTH/4)
      @x = (@x+@width > xmax) ? xmax-@width : (@x<xmin) ? xmin : @x;
    end
  
    def render args
      args.outputs.solids << [@x,@y,@width,@height,255,0,0];
    end
  
    def rect
      [@x, @y, @width, @height]
    end
  end

#+end_src

*** Physics And Collisions - Arbitrary Collision - rectangle.rb
#+begin_src ruby
  # ./samples/04_physics_and_collisions/09_arbitrary_collision/app/rectangle.rb
  class Rectangle
    def initialize args
  
      @image = "sprites/roundSquare_white.png"
      @width  = 160.0
      @height = 80.0
      @x=$args.grid.right/2.0 - @width/2.0
      @y=$args.grid.top/2.0 - @height/2.0
  
      @xtmp = @width  * (1.0/10.0)
      @ytmp = @height * (1.0/10.0)
  
      #ball0 = args.state.balls[0]
      #hypotenuse = (args.state.balls[0].width**2 + args.state.balls[0].height**2)**0.5
      hypotenuse=args.state.ball_hypotenuse
      @boldXY = {x:(@x-hypotenuse/2)-1, y:(@y-hypotenuse/2)-1}
      @boldWidth = @width + hypotenuse + 2
      @boldHeight = @height + hypotenuse + 2
      @bold = [(@x-hypotenuse/2)-1,(@y-hypotenuse/2)-1,@width + hypotenuse + 2,@height + hypotenuse + 2]
  
  
      @points = [
        {x:@x,        y:@y+@ytmp},
        {x:@x+@xtmp,        y:@y},
        {x:@x+@width-@xtmp, y:@y},
        {x:@x+@width, y:@y+@ytmp},
        {x:@x+@width, y:@y+@height-@ytmp},#
        {x:@x+@width-@xtmp, y:@y+@height},
        {x:@x+@xtmp,        y:@y+@height},
        {x:@x,        y:@y+@height-@ytmp}
      ]
  
      @colliders = []
      #i = 0
      #while i < @points.length-1
        #@colliders.append(LinearCollider.new(@points[i],@points[i+1],:pos))
        #i+=1
      #end
      @colliders.append(LinearCollider.new(@points[0],@points[1], :neg))
      @colliders.append(LinearCollider.new(@points[1],@points[2], :neg))
      @colliders.append(LinearCollider.new(@points[2],@points[3], :neg))
      @colliders.append(LinearCollider.new(@points[3],@points[4], :neg))
      @colliders.append(LinearCollider.new(@points[4],@points[5], :pos))
      @colliders.append(LinearCollider.new(@points[5],@points[6], :pos))
      @colliders.append(LinearCollider.new(@points[6],@points[7], :pos))
      @colliders.append(LinearCollider.new(@points[0],@points[7], :pos))
  
    end
  
    def update args
  
      for b in args.state.balls
        if [b.x, b.y, b.width, b.height].intersect_rect?(@bold)
          for c in @colliders
            if c.collision?(args, b.getPoints(args),b)
              c.collide args, b
            end
          end
        end
      end
    end
  
    def draw args
      args.outputs.sprites << [
        @x,                                       # X
        @y,                                       # Y
        @width,                                   # W
        @height,                                  # H
        @image,                                   # PATH
        0,                                        # ANGLE
        255,                                      # ALPHA
        219,                                      # RED_SATURATION
        112,                                      # GREEN_SATURATION
        147                                       # BLUE_SATURATION
      ]
      #args.outputs.sprites << [@x, @y, @width, @height, "sprites/roundSquare_small_black.png"]
    end
  
    def serialize
    	{x: @x, y:@y}
    end
  
    def inspect
    	serialize.to_s
    end
  
    def to_s
    	serialize.to_s
    end
  end

#+end_src

*** Physics And Collisions - Arbitrary Collision - square_collider.rb
#+begin_src ruby
  # ./samples/04_physics_and_collisions/09_arbitrary_collision/app/square_collider.rb
  
  class SquareCollider
    def initialize x,y,direction,size=COLLISIONWIDTH
      @x = x
      @y = y
      @size = size
      @direction = direction
  
    end
    def collision? args, ball
      #args.outputs.solids <<  [@x, @y, @size, @size,     000, 255, 255]
  
  
      return [@x,@y,@size,@size].intersect_rect?([ball.x,ball.y,ball.width,ball.height])
    end
  
    def collide args, ball
      vmag = (ball.velocity.x**2.0 +ball.velocity.y**2.0)**0.5
      a = ((2.0**0.5)*vmag)/2.0
      if vmag < MAX_VELOCITY
        ball.velocity.x = (a) * @direction.x * 1.1
        ball.velocity.y = (a) * @direction.y * 1.1
      else
        ball.velocity.x = (a) * @direction.x
        ball.velocity.y = (a) * @direction.y
      end
  
    end
  end

#+end_src

*** Physics And Collisions - Arbitrary Collision - vector2d.rb
#+begin_src ruby
  # ./samples/04_physics_and_collisions/09_arbitrary_collision/app/vector2d.rb
  class Vector2d
      attr_accessor :x, :y
    
      def initialize x=0, y=0
        @x=x
        @y=y
      end
    
      #returns a vector multiplied by scalar x
      #x [float] scalar
      def mult x
        r = Vector2d.new(0,0)
        r.x=@x*x
        r.y=@y*x
        r
      end
    
      # vect [Vector2d] vector to copy
      def copy vect
        Vector2d.new(@x, @y)
      end
    
      #returns a new vector equivalent to this+vect
      #vect [Vector2d] vector to add to self
      def add vect
        Vector2d.new(@x+vect.x,@y+vect.y)
      end
    
      #returns a new vector equivalent to this-vect
      #vect [Vector2d] vector to subtract to self
      def sub vect
        Vector2d.new(@x-vect.c, @y-vect.y)
      end
    
      #return the magnitude of the vector
      def mag
        ((@x**2)+(@y**2))**0.5
      end
    
      #returns a new normalize version of the vector
      def normalize
        Vector2d.new(@x/mag, @y/mag)
      end
    
      #TODO delet?
      def distABS vect
        (((vect.x-@x)**2+(vect.y-@y)**2)**0.5).abs()
      end
    end
#+end_src

*** Physics And Collisions - Collision With Object Removal - ball.rb
#+begin_src ruby
  # ./samples/04_physics_and_collisions/10_collision_with_object_removal/app/ball.rb
  class Ball
    #TODO limit accessors?
    attr_accessor :xy, :width, :height, :velocity
  
  
    #@xy [Vector2d] x,y position
    #@velocity [Vector2d] velocity of ball
    def initialize
      @xy = Vector2d.new(WIDTH/2,500)
      @velocity = Vector2d.new(4,-4)
      @width =  20
      @height = 20
    end
  
    #move the ball according to its velocity
    def update args
      @xy.x+=@velocity.x
      @xy.y+=@velocity.y
    end
  
    #render the ball to the screen
    def render args
      args.outputs.solids << [@xy.x,@xy.y,@width,@height,255,0,255];
      #args.outputs.labels << [20,HEIGHT-50,"velocity: " +@velocity.x.to_s+","+@velocity.y.to_s + "   magnitude:" + @velocity.mag.to_s]
    end
  
    def rect
      [@xy.x,@xy.y,@width,@height]
    end
  
  end

#+end_src

*** Physics And Collisions - Collision With Object Removal - linear_collider.rb
#+begin_src ruby
  # ./samples/04_physics_and_collisions/10_collision_with_object_removal/app/linear_collider.rb
  #The LinearCollider (theoretically) produces collisions upon a line segment defined point.y two x,y cordinates
  
  class LinearCollider
  
    #start [Array of length 2] start of the line segment as a x,y cordinate
    #last [Array of length 2] end of the line segment as a x,y cordinate
  
    #inorder for the LinearCollider to be functional the line segment must be said to have a thickness
    #(as it is unlikly that a colliding object will land exactly on the linesegment)
  
    #extension defines if the line's thickness extends negatively or positively
    #extension :pos     extends positively
    #extension :neg     extends negatively
  
    #thickness [float] how thick the line should be (should always be atleast as large as the magnitude of the colliding object)
    def initialize (pointA, pointB, extension=:neg, thickness=10)
      @pointA = pointA
      @pointB = pointB
      @thickness = thickness
      @extension = extension
  
      @pointAExtended={
        x: @pointA.x + @thickness*(@extension == :neg ? -1 : 1),
        y: @pointA.y + @thickness*(@extension == :neg ? -1 : 1)
      }
      @pointBExtended={
        x: @pointB.x + @thickness*(@extension == :neg ? -1 : 1),
        y: @pointB.y + @thickness*(@extension == :neg ? -1 : 1)
      }
  
    end
  
    def resetPoints(pointA,pointB)
      @pointA = pointA
      @pointB = pointB
  
      @pointAExtended={
        x:@pointA.x + @thickness*(@extension == :neg ? -1 : 1),
        y:@pointA.y + @thickness*(@extension == :neg ? -1 : 1)
      }
      @pointBExtended={
        x:@pointB.x + @thickness*(@extension == :neg ? -1 : 1),
        y:@pointB.y + @thickness*(@extension == :neg ? -1 : 1)
      }
    end
  
    #TODO: Ugly function
    def slope (pointA, pointB)
      return (pointB.x==pointA.x) ? INFINITY : (pointB.y+-pointA.y)/(pointB.x+-pointA.x)
    end
  
    #TODO: Ugly function
    def intercept(pointA, pointB)
      if (slope(pointA, pointB) == INFINITY)
        -INFINITY
      elsif slope(pointA, pointB) == -1*INFINITY
        INFINITY
      else
        pointA.y+-1.0*(slope(pointA, pointB)*pointA.x)
      end
    end
  
    def calcY(pointA, pointB, x)
      return slope(pointA, pointB)*x + intercept(pointA, pointB)
    end
  
    #test if a collision has occurred
    def isCollision? (point)
      #INFINITY slop breaks down when trying to determin collision, ergo it requires a special test
      if slope(@pointA, @pointB) ==  INFINITY &&
        point.x >= [@pointA.x,@pointB.x].min+(@extension == :pos ? -@thickness : 0) &&
        point.x <= [@pointA.x,@pointB.x].max+(@extension == :neg ?  @thickness : 0) &&
        point.y >= [@pointA.y,@pointB.y].min && point.y <= [@pointA.y,@pointB.y].max
          return true
      end
  
      isNegInLine   = @extension == :neg &&
                      point.y <= slope(@pointA, @pointB)*point.x+intercept(@pointA,@pointB) &&
                      point.y >= point.x*slope(@pointAExtended, @pointBExtended)+intercept(@pointAExtended,@pointBExtended)
      isPosInLine   = @extension == :pos &&
                      point.y >= slope(@pointA, @pointB)*point.x+intercept(@pointA,@pointB) &&
                      point.y <= point.x*slope(@pointAExtended, @pointBExtended)+intercept(@pointAExtended,@pointBExtended)
      isInBoxBounds = point.x >= [@pointA.x,@pointB.x].min &&
                      point.x <= [@pointA.x,@pointB.x].max &&
                      point.y >= [@pointA.y,@pointB.y].min+(@extension == :neg ? -@thickness : 0) &&
                      point.y <= [@pointA.y,@pointB.y].max+(@extension == :pos ? @thickness : 0)
  
      return isInBoxBounds && (isNegInLine || isPosInLine)
  
    end
  
    def getRepelMagnitude (fbx, fby, vrx, vry, args)
      a = fbx ; b = vrx ; c = fby
      d = vry ; e = args.state.ball.velocity.mag
  
      if b**2 + d**2 == 0
        puts "magnitude error"
      end
  
      x1 = (-a*b+-c*d + (e**2 * b**2 - b**2 * c**2 + 2*a*b*c*d + e**2 + d**2 - a**2 * d**2)**0.5)/(b**2 + d**2)
      x2 = -((a*b + c*d + (e**2 * b**2 - b**2 * c**2 + 2*a*b*c*d + e**2 * d**2 - a**2 * d**2)**0.5)/(b**2 + d**2))
      return ((a+x1*b)**2 + (c+x1*d)**2 == e**2) ? x1 : x2
    end
  
    def update args
      #each of the four points on the square ball - NOTE simple to extend to a circle
      points= [ {x: args.state.ball.xy.x,                          y: args.state.ball.xy.y},
                {x: args.state.ball.xy.x+args.state.ball.width,    y: args.state.ball.xy.y},
                {x: args.state.ball.xy.x,                          y: args.state.ball.xy.y+args.state.ball.height},
                {x: args.state.ball.xy.x+args.state.ball.width,    y: args.state.ball.xy.y + args.state.ball.height}
              ]
  
      #for each point p in points
      for point in points
        #isCollision.md has more information on this section
        #TODO: section can certainly be simplifyed
        if isCollision?(point)
          u = Vector2d.new(1.0,((slope(@pointA, @pointB)==0) ? INFINITY : -1/slope(@pointA, @pointB))*1.0).normalize #normal perpendicular (to line segment) vector
  
          #the vector with the repeling force can be u or -u depending of where the ball was coming from in relation to the line segment
          previousBallPosition=Vector2d.new(point.x-args.state.ball.velocity.x,point.y-args.state.ball.velocity.y)
          choiceA = (u.mult(1))
          choiceB =  (u.mult(-1))
          vectorRepel = nil
  
          if (slope(@pointA, @pointB))!=INFINITY && u.y < 0
            choiceA, choiceB = choiceB, choiceA
          end
          vectorRepel = (previousBallPosition.y > calcY(@pointA, @pointB, previousBallPosition.x)) ? choiceA : choiceB
  
          #vectorRepel = (previousBallPosition.y > slope(@pointA, @pointB)*previousBallPosition.x+intercept(@pointA,@pointB)) ? choiceA : choiceB)
          if (slope(@pointA, @pointB) == INFINITY) #slope INFINITY breaks down in the above test, ergo it requires a custom test
            vectorRepel = (previousBallPosition.x > @pointA.x) ? (u.mult(1)) : (u.mult(-1))
          end
          #puts ("     " + $t[0].to_s + "," + $t[1].to_s + "    " + $t[2].to_s + "," + $t[3].to_s + "     " + "   " + u.x.to_s + "," + u.y.to_s)
          #vectorRepel now has the repeling force
  
          mag = args.state.ball.velocity.mag
          theta_ball=Math.atan2(args.state.ball.velocity.y,args.state.ball.velocity.x) #the angle of the ball's velocity
          theta_repel=Math.atan2(vectorRepel.y,vectorRepel.x) #the angle of the repeling force
          #puts ("theta:" + theta_ball.to_s + " " + theta_repel.to_s) #theta okay
  
          fbx = mag * Math.cos(theta_ball) #the x component of the ball's velocity
          fby = mag * Math.sin(theta_ball) #the y component of the ball's velocity
  
          repelMag = getRepelMagnitude(fbx, fby, vectorRepel.x, vectorRepel.y, args)
  
          frx = repelMag* Math.cos(theta_repel) #the x component of the repel's velocity | magnitude is set to twice of fbx
          fry = repelMag* Math.sin(theta_repel) #the y component of the repel's velocity | magnitude is set to twice of fby
  
          fsumx = fbx+frx #sum of x forces
          fsumy = fby+fry #sum of y forces
          fr = mag#fr is the resulting magnitude
          thetaNew = Math.atan2(fsumy, fsumx)  #thetaNew is the resulting angle
          xnew = fr*Math.cos(thetaNew) #resulting x velocity
          ynew = fr*Math.sin(thetaNew) #resulting y velocity
  
          args.state.ball.velocity = Vector2d.new(xnew,ynew)
          #args.state.ball.xy.add(args.state.ball.velocity)
          break #no need to check the other points ?
        else
        end
      end
    end #end update
  
  end

#+end_src

*** Physics And Collisions - Collision With Object Removal - main.rb
#+begin_src ruby
  # ./samples/04_physics_and_collisions/10_collision_with_object_removal/app/main.rb
  # coding: utf-8
  INFINITY= 10**10
  WIDTH=1280
  HEIGHT=720
  
  require 'app/vector2d.rb'
  require 'app/paddle.rb'
  require 'app/ball.rb'
  require 'app/linear_collider.rb'
  
  #Method to init default values
  def defaults args
    args.state.game_board ||= [(args.grid.w / 2 - args.grid.w / 4), 0, (args.grid.w / 2), args.grid.h]
    args.state.bricks ||= []
    args.state.num_bricks ||= 0
    args.state.game_over_at ||= 0
    args.state.paddle ||= Paddle.new
    args.state.ball   ||= Ball.new
    args.state.westWall  ||= LinearCollider.new({x: args.grid.w/4,      y: 0},          {x: args.grid.w/4,      y: args.grid.h}, :pos)
    args.state.eastWall  ||= LinearCollider.new({x: 3*args.grid.w*0.25, y: 0},          {x: 3*args.grid.w*0.25, y: args.grid.h})
    args.state.southWall ||= LinearCollider.new({x: 0,                  y: 0},          {x: args.grid.w,        y: 0})
    args.state.northWall ||= LinearCollider.new({x: 0,                  y:args.grid.h}, {x: args.grid.w,        y: args.grid.h}, :pos)
  
    #args.state.testWall ||= LinearCollider.new({x:0 , y:0},{x:args.grid.w, y:args.grid.h})
  end
  
  #Render loop
  def render args
    render_instructions args
    render_board args
    render_bricks args
  end
  
  begin :render_methods
    #Method to display the instructions of the game
    def render_instructions args
      args.outputs.labels << [225, args.grid.h - 30, "← and → to move the paddle left and right",  0, 1]
    end
  
    def render_board args
      args.outputs.borders << args.state.game_board
    end
  
    def render_bricks args
      args.outputs.solids << args.state.bricks.map(&:rect)
    end
  end
  
  #Calls all methods necessary for performing calculations
  def calc args
    add_new_bricks args
    reset_game args
    calc_collision args
    win_game args
  
    args.state.westWall.update args
    args.state.eastWall.update args
    args.state.southWall.update args
    args.state.northWall.update args
    args.state.paddle.update args
    args.state.ball.update args
  
    #args.state.testWall.update args
  
    args.state.paddle.render args
    args.state.ball.render args
  end
  
  begin :calc_methods
    def add_new_bricks args
      return if args.state.num_bricks > 40
  
      #Width of the game board is 640px
      brick_width = (args.grid.w / 2) / 10
      brick_height = brick_width / 2
  
      (4).map_with_index do |y|
        #Make a box that is 10 bricks wide and 4 bricks tall
        args.state.bricks += (10).map_with_index do |x|
          args.state.new_entity(:brick) do |b|
            b.x = x * brick_width + (args.grid.w / 2 - args.grid.w / 4)
            b.y = args.grid.h - ((y + 1) * brick_height)
            b.rect = [b.x + 1, b.y - 1, brick_width - 2, brick_height - 2, 235, 50 * y, 52]
  
            #Add linear colliders to the brick
            b.collider_bottom = LinearCollider.new([(b.x-2), (b.y-5)], [(b.x+brick_width+1), (b.y-5)], :pos, brick_height)
            b.collider_right = LinearCollider.new([(b.x+brick_width+1), (b.y-5)], [(b.x+brick_width+1), (b.y+brick_height+1)], :pos)
            b.collider_left = LinearCollider.new([(b.x-2), (b.y-5)], [(b.x-2), (b.y+brick_height+1)], :neg)
            b.collider_top = LinearCollider.new([(b.x-2), (b.y+brick_height+1)], [(b.x+brick_width+1), (b.y+brick_height+1)], :neg)
  
            # @xyCollision  = LinearCollider.new({x: @x,y: @y+@height}, {x: @x+@width, y: @y+@height})
            # @xyCollision2 = LinearCollider.new({x: @x,y: @y}, {x: @x+@width, y: @y}, :pos)
            # @xyCollision3 = LinearCollider.new({x: @x,y: @y}, {x: @x, y: @y+@height})
            # @xyCollision4 = LinearCollider.new({x: @x+@width,y: @y}, {x: @x+@width, y: @y+@height}, :pos)
  
            b.broken = false
  
            args.state.num_bricks += 1
          end
        end
      end
    end
  
    def reset_game args
      if args.state.ball.xy.y < 20 && args.state.game_over_at.elapsed_time > 60
        #Freeze the ball
        args.state.ball.velocity.x = 0
        args.state.ball.velocity.y = 0
        #Freeze the paddle
        args.state.paddle.enabled = false
  
        args.state.game_over_at = args.state.tick_count
      end
  
      if args.state.game_over_at.elapsed_time < 60 && args.state.tick_count > 60 && args.state.bricks.count != 0
        #Display a "Game over" message
        args.outputs.labels << [100, 100, "GAME OVER", 10]
      end
  
      #If 60 frames have passed since the game ended, restart the game
      if args.state.game_over_at != 0 && args.state.game_over_at.elapsed_time == 60
        # FIXME: only put value types in state
        args.state.ball = Ball.new
  
        # FIXME: only put value types in state
        args.state.paddle = Paddle.new
  
        args.state.bricks = []
        args.state.num_bricks = 0
      end
    end
  
    def calc_collision args
      #Remove the brick if it is hit with the ball
      ball = args.state.ball
      ball_rect = [ball.xy.x, ball.xy.y, 20, 20]
  
      #Loop through each brick to see if the ball is colliding with it
      args.state.bricks.each do |b|
        if b.rect.intersect_rect?(ball_rect)
          #Run the linear collider for the brick if there is a collision
          b[:collider_bottom].update args
          b[:collider_right].update args
          b[:collider_left].update args
          b[:collider_top].update args
  
          b.broken = true
        end
      end
  
      args.state.bricks = args.state.bricks.reject(&:broken)
    end
  
    def win_game args
      if args.state.bricks.count == 0 && args.state.game_over_at.elapsed_time > 60
        #Freeze the ball
        args.state.ball.velocity.x = 0
        args.state.ball.velocity.y = 0
        #Freeze the paddle
        args.state.paddle.enabled = false
  
        args.state.game_over_at = args.state.tick_count
      end
  
      if args.state.game_over_at.elapsed_time < 60 && args.state.tick_count > 60 && args.state.bricks.count == 0
        #Display a "Game over" message
        args.outputs.labels << [100, 100, "CONGRATULATIONS!", 10]
      end
    end
  
  end
  
  def tick args
    defaults args
    render args
    calc args
  
    #args.outputs.lines << [0, 0, args.grid.w, args.grid.h]
  
    #$tc+=1
    #if $tc == 5
      #$train << [args.state.ball.xy.x, args.state.ball.xy.y]
      #$tc = 0
    #end
    #for t in $train
  
      #args.outputs.solids << [t[0],t[1],5,5,255,0,0];
    #end
  end

#+end_src

*** Physics And Collisions - Collision With Object Removal - paddle.rb
#+begin_src ruby
  # ./samples/04_physics_and_collisions/10_collision_with_object_removal/app/paddle.rb
  class Paddle
    attr_accessor :enabled
  
    def initialize ()
      @x=WIDTH/2
      @y=100
      @width=100
      @height=20
      @speed=10
  
      @xyCollision  = LinearCollider.new({x: @x,y: @y+@height+5}, {x: @x+@width, y: @y+@height+5})
      @xyCollision2 = LinearCollider.new({x: @x,y: @y}, {x: @x+@width, y: @y}, :pos)
      @xyCollision3 = LinearCollider.new({x: @x,y: @y}, {x: @x, y: @y+@height+5})
      @xyCollision4 = LinearCollider.new({x: @x+@width,y: @y}, {x: @x+@width, y: @y+@height+5}, :pos)
  
      @enabled = true
    end
  
    def update args
      @xyCollision.resetPoints({x: @x,y: @y+@height+5}, {x: @x+@width, y: @y+@height+5})
      @xyCollision2.resetPoints({x: @x,y: @y}, {x: @x+@width, y: @y})
      @xyCollision3.resetPoints({x: @x,y: @y}, {x: @x, y: @y+@height+5})
      @xyCollision4.resetPoints({x: @x+@width,y: @y}, {x: @x+@width, y: @y+@height+5})
  
      @xyCollision.update  args
      @xyCollision2.update args
      @xyCollision3.update args
      @xyCollision4.update args
  
      args.inputs.keyboard.key_held.left  ||= false
      args.inputs.keyboard.key_held.right  ||= false
  
      if not (args.inputs.keyboard.key_held.left == args.inputs.keyboard.key_held.right)
        if args.inputs.keyboard.key_held.left && @enabled
          @x-=@speed
        elsif args.inputs.keyboard.key_held.right && @enabled
          @x+=@speed
        end
      end
  
      xmin =WIDTH/4
      xmax = 3*(WIDTH/4)
      @x = (@x+@width > xmax) ? xmax-@width : (@x<xmin) ? xmin : @x;
    end
  
    def render args
      args.outputs.solids << [@x,@y,@width,@height,255,0,0];
    end
  
    def rect
      [@x, @y, @width, @height]
    end
  end

#+end_src

*** Physics And Collisions - Collision With Object Removal - tests.rb
#+begin_src ruby
  # ./samples/04_physics_and_collisions/10_collision_with_object_removal/app/tests.rb
  # For advanced users:
  # You can put some quick verification tests here, any method
  # that starts with the `test_` will be run when you save this file.
  
  # Here is an example test and game
  
  # To run the test: ./dragonruby mygame --eval app/tests.rb --no-tick
  
  class MySuperHappyFunGame
    attr_gtk
  
    def tick
      outputs.solids << [100, 100, 300, 300]
    end
  end
  
  def test_universe args, assert
    game = MySuperHappyFunGame.new
    game.args = args
    game.tick
    assert.true!  args.outputs.solids.length == 1, "failure: a solid was not added after tick"
    assert.false! 1 == 2, "failure: some how, 1 equals 2, the world is ending"
    puts "test_universe completed successfully"
  end
  
  puts "running tests"
  $gtk.reset 100
  $gtk.log_level = :off
  $gtk.tests.start

#+end_src

*** Physics And Collisions - Collision With Object Removal - vector2d.rb
#+begin_src ruby
  # ./samples/04_physics_and_collisions/10_collision_with_object_removal/app/vector2d.rb
  
  class Vector2d
    attr_accessor :x, :y
  
    def initialize x=0, y=0
      @x=x
      @y=y
    end
  
    #returns a vector multiplied by scalar x
    #x [float] scalar
    def mult x
      r = Vector2d.new(0,0)
      r.x=@x*x
      r.y=@y*x
      r
    end
  
    # vect [Vector2d] vector to copy
    def copy vect
      Vector2d.new(@x, @y)
    end
  
    #returns a new vector equivalent to this+vect
    #vect [Vector2d] vector to add to self
    def add vect
      Vector2d.new(@x+vect.x,@y+vect.y)
    end
  
    #returns a new vector equivalent to this-vect
    #vect [Vector2d] vector to subtract to self
    def sub vect
      Vector2d.new(@x-vect.c, @y-vect.y)
    end
  
    #return the magnitude of the vector
    def mag
      ((@x**2)+(@y**2))**0.5
    end
  
    #returns a new normalize version of the vector
    def normalize
      Vector2d.new(@x/mag, @y/mag)
    end
  
    #TODO delet?
    def distABS vect
      (((vect.x-@x)**2+(vect.y-@y)**2)**0.5).abs()
    end
  end

#+end_src

*** Mouse - Mouse Click - main.rb
#+begin_src ruby
  # ./samples/05_mouse/01_mouse_click/app/main.rb
  =begin
  
   APIs listing that haven't been encountered in previous sample apps:
  
   - product: Returns an array of all combinations of elements from all arrays.
  
     For example, [1,2].product([1,2]) would return the following array...
     [[1,1], [1,2], [2,1], [2,2]]
     More than two arrays can be given to product and it will still work,
     such as [1,2].product([1,2],[3,4]). What would product return in this case?
  
     Answer:
     [[1,1,3],[1,1,4],[1,2,3],[1,2,4],[2,1,3],[2,1,4],[2,2,3],[2,2,4]]
  
   - num1.fdiv(num2): Returns the float division (will have a decimal) of the two given numbers.
     For example, 5.fdiv(2) = 2.5 and 5.fdiv(5) = 1.0
  
   - yield: Allows you to call a method with a code block and yield to that block.
  
   Reminders:
  
   - ARRAY#inside_rect?: Returns true or false depending on if the point is inside the rect.
  
   - String interpolation: Uses #{} syntax; everything between the #{ and the } is evaluated
     as Ruby code, and the placeholder is replaced with its corresponding value or result.
  
   - args.inputs.mouse.click: This property will be set if the mouse was clicked.
  
   - Ternary operator (?): Will evaluate a statement (just like an if statement)
     and perform an action if the result is true or another action if it is false.
  
   - reject: Removes elements from a collection if they meet certain requirements.
  
   - args.outputs.borders: An array. The values generate a border.
     The parameters are [X, Y, WIDTH, HEIGHT, RED, GREEN, BLUE]
     For more information about borders, go to mygame/documentation/03-solids-and-borders.md.
  
   - args.outputs.labels: An array. The values generate a label.
     The parameters are [X, Y, TEXT, SIZE, ALIGNMENT, RED, GREEN, BLUE, ALPHA, FONT STYLE]
     For more information about labels, go to mygame/documentation/02-labels.
  
  =end
  
  # This sample app is a classic game of Tic Tac Toe.
  
  class TicTacToe
    attr_accessor :_, :state, :outputs, :inputs, :grid, :gtk
  
    # Starts the game with player x's turn and creates an array (to_a) for space combinations.
    # Calls methods necessary for the game to run properly.
    def tick
      init_new_game
      render_board
      input_board
    end
  
    def init_new_game
      state.current_turn       ||= :x
      state.space_combinations ||= [-1, 0, 1].product([-1, 0, 1]).to_a
  
      state.spaces             ||= {}
  
      state.space_combinations.each do |x, y|
        state.spaces[x]    ||= {}
        state.spaces[x][y] ||= state.new_entity(:space)
      end
    end
  
    # Uses borders to create grid squares for the game's board. Also outputs the game pieces using labels.
    def render_board
      square_size = 80
  
      # Positions the game's board in the center of the screen.
      # Try removing what follows grid.w_half or grid.h_half and see how the position changes!
      board_left = grid.w_half - square_size * 1.5
      board_top  = grid.h_half - square_size * 1.5
  
      # At first glance, the add(1) looks pretty trivial. But if you remove it,
      # you'll see that the positioning of the board would be skewed without it!
      # Or if you put 2 in the parenthesis, the pieces will be placed in the wrong squares
      # due to the change in board placement.
      outputs.borders << all_spaces do |x, y, space| # outputs borders for all board spaces
        space.border ||= [
          board_left + x.add(1) * square_size, # space.border is initialized using this definition
          board_top  + y.add(1) * square_size,
          square_size,
          square_size
        ]
      end
  
      # Again, the calculations ensure that the piece is placed in the center of the grid square.
      # Remove the '- 20' and the piece will be placed at the top of the grid square instead of the center.
      outputs.labels << filled_spaces do |x, y, space| # put label in each filled space of board
            label board_left + x.add(1) * square_size + square_size.fdiv(2),
            board_top  + y.add(1) * square_size + square_size - 20,
            space.piece # text of label, either "x" or "o"
      end
  
      # Uses a label to output whether x or o won, or if a draw occurred.
      # If the game is ongoing, a label shows whose turn it currently is.
      outputs.labels << if state.x_won
                          label grid.w_half, grid.top - 80, "x won" # the '-80' positions the label 80 pixels lower than top
                        elsif state.o_won
                          label grid.w_half, grid.top - 80, "o won" # grid.w_half positions the label in the center horizontally
                        elsif state.draw
                          label grid.w_half, grid.top - 80, "a draw"
                        else # if no one won and the game is ongoing
                          label grid.w_half, grid.top - 80, "turn: #{state.current_turn}"
                        end
    end
  
    # Calls the methods responsible for handling user input and determining the winner.
    # Does nothing unless the mouse is clicked.
    def input_board
      return unless inputs.mouse.click
      input_place_piece
      input_restart_game
      determine_winner
    end
  
    # Handles user input for placing pieces on the board.
    def input_place_piece
      return if state.game_over
  
      # Checks to find the space that the mouse was clicked inside of, and makes sure the space does not already
      # have a piece in it.
      __, __, space = all_spaces.find do |__, __, space|
        inputs.mouse.click.point.inside_rect?(space.border) && !space.piece
      end
  
      # The piece that goes into the space belongs to the player whose turn it currently is.
      return unless space
      space.piece = state.current_turn
  
      # This ternary operator statement allows us to change the current player's turn.
      # If it is currently x's turn, it becomes o's turn. If it is not x's turn, it become's x's turn.
      state.current_turn = state.current_turn == :x ? :o : :x
    end
  
    # Resets the game.
    def input_restart_game
      return unless state.game_over
      gtk.reset
      init_new_game
    end
  
    # Checks if x or o won the game.
    # If neither player wins and all nine squares are filled, a draw happens.
    # Once a player is chosen as the winner or a draw happens, the game is over.
    def determine_winner
      state.x_won = won? :x # evaluates to either true or false (boolean values)
      state.o_won = won? :o
      state.draw = true if filled_spaces.length == 9 && !state.x_won && !state.o_won
      state.game_over = state.x_won || state.o_won || state.draw
    end
  
    # Determines if a player won by checking if there is a horizontal match or vertical match.
    # Horizontal_match and vertical_match have boolean values. If either is true, the game has been won.
    def won? piece
      # performs action on all space combinations
      won = [[-1, 0, 1]].product([-1, 0, 1]).map do |xs, y|
  
        # Checks if the 3 grid spaces with the same y value (or same row) and
        # x values that are next to each other have pieces that belong to the same player.
        # Remember, the value of piece is equal to the current turn (which is the player).
        horizontal_match = state.spaces[xs[0]][y].piece == piece &&
                           state.spaces[xs[1]][y].piece == piece &&
                           state.spaces[xs[2]][y].piece == piece
  
        # Checks if the 3 grid spaces with the same x value (or same column) and
        # y values that are next to each other have pieces that belong to the same player.
        # The && represents an "and" statement: if even one part of the statement is false,
        # the entire statement evaluates to false.
        vertical_match = state.spaces[y][xs[0]].piece == piece &&
                         state.spaces[y][xs[1]].piece == piece &&
                         state.spaces[y][xs[2]].piece == piece
  
        horizontal_match || vertical_match # if either is true, true is returned
      end
  
      # Sees if there is a diagonal match, starting from the bottom left and ending at the top right.
      # Is added to won regardless of whether the statement is true or false.
      won << (state.spaces[-1][-1].piece == piece && # bottom left
              state.spaces[ 0][ 0].piece == piece && # center
              state.spaces[ 1][ 1].piece == piece)   # top right
  
      # Sees if there is a diagonal match, starting at the bottom right and ending at the top left
      # and is added to won.
      won << (state.spaces[ 1][-1].piece == piece && # bottom right
              state.spaces[ 0][ 0].piece == piece && # center
              state.spaces[-1][ 1].piece == piece)   # top left
  
      # Any false statements (meaning false diagonal matches) are rejected from won
      won.reject_false.any?
    end
  
    # Defines filled spaces on the board by rejecting all spaces that do not have game pieces in them.
    # The ! before a statement means "not". For example, we are rejecting any space combinations that do
    # NOT have pieces in them.
    def filled_spaces
      state.space_combinations
        .reject { |x, y| !state.spaces[x][y].piece } # reject spaces with no pieces in them
        .map do |x, y|
          if block_given?
            yield x, y, state.spaces[x][y]
          else
            [x, y, state.spaces[x][y]] # sets definition of space
          end
      end
    end
  
    # Defines all spaces on the board.
    def all_spaces
      if !block_given?
        state.space_combinations.map do |x, y|
          [x, y, state.spaces[x][y]] # sets definition of space
        end
      else # if a block is given (block_given? is true)
        state.space_combinations.map do |x, y|
          yield x, y, state.spaces[x][y] # yield if a block is given
        end
      end
    end
  
    # Sets values for a label, such as the position, value, size, alignment, and color.
    def label x, y, value
      [x, y + 10, value, 20, 1, 0, 0, 0]
    end
  end
  
  $tic_tac_toe = TicTacToe.new
  
  def tick args
    $tic_tac_toe._       = args
    $tic_tac_toe.state   = args.state
    $tic_tac_toe.outputs = args.outputs
    $tic_tac_toe.inputs  = args.inputs
    $tic_tac_toe.grid    = args.grid
    $tic_tac_toe.gtk     = args.gtk
    $tic_tac_toe.tick
    tick_instructions args, "Sample app shows how to work with mouse clicks."
  end
  
  def tick_instructions args, text, y = 715
    return if args.state.key_event_occurred
    if args.inputs.mouse.click ||
       args.inputs.keyboard.directional_vector ||
       args.inputs.keyboard.key_down.enter ||
       args.inputs.keyboard.key_down.escape
      args.state.key_event_occurred = true
    end
  
    args.outputs.debug << [0, y - 50, 1280, 60].solid
    args.outputs.debug << [640, y, text, 1, 1, 255, 255, 255].label
    args.outputs.debug << [640, y - 25, "(click to dismiss instructions)" , -2, 1, 255, 255, 255].label
  end

#+end_src

*** Mouse - Mouse Move - main.rb
#+begin_src ruby
  # ./samples/05_mouse/02_mouse_move/app/main.rb
  =begin
  
   Reminders:
  
   - num1.greater(num2): Returns the greater value.
     For example, if we have the command
     puts 4.greater(3)
     the number 4 would be printed to the console since it has a greater value than 3.
     Similar to lesser, which returns the lesser value.
  
   - find_all: Finds all elements of a collection that meet certain requirements.
     For example, in this sample app, we're using find_all to find all zombies that have intersected
     or hit the player's sprite since these zombies have been killed.
  
   - args.inputs.keyboard.key_down.KEY: Determines if a key is being held or pressed.
     Stores the frame the "down" event occurred.
     For more information about the keyboard, go to mygame/documentation/06-keyboard.md.
  
   - args.outputs.sprites: An array. The values generate a sprite.
     The parameters are [X, Y, WIDTH, HEIGHT, PATH, ANGLE, ALPHA, RED, GREEN, BLUE]
     For more information about sprites, go to mygame/documentation/05-sprites.md.
  
   - args.state.new_entity: Used when we want to create a new object, like a sprite or button.
     When we want to create a new object, we can declare it as a new entity and then define
     its properties. (Remember, you can use state to define ANY property and it will
     be retained across frames.)
  
   - String interpolation: Uses #{} syntax; everything between the #{ and the } is evaluated
     as Ruby code, and the placeholder is replaced with its corresponding value or result.
  
   - map: Ruby method used to transform data; used in arrays, hashes, and collections.
     Can be used to perform an action on every element of a collection, such as multiplying
     each element by 2 or declaring every element as a new entity.
  
   - sample: Chooses a random element from the array.
  
   - reject: Removes elements that meet certain requirements.
     In this sample app, we're removing/rejecting zombies that reach the center of the screen. We're also
     rejecting zombies that were killed more than 30 frames ago.
  
  =end
  
  # This sample app allows users to move around the screen in order to kill zombies. Zombies appear from every direction so the goal
  # is to kill the zombies as fast as possible!
  
  class ProtectThePuppiesFromTheZombies
    attr_accessor :grid, :inputs, :state, :outputs
  
    # Calls the methods necessary for the game to run properly.
    def tick
      defaults
      render
      calc
      input
    end
  
    # Sets default values for the zombies and for the player.
    # Initialization happens only in the first frame.
    def defaults
      state.flash_at               ||= 0
      state.zombie_min_spawn_rate  ||= 60
      state.zombie_spawn_countdown ||= random_spawn_countdown state.zombie_min_spawn_rate
      state.zombies                ||= []
      state.killed_zombies         ||= []
  
      # Declares player as a new entity and sets its properties.
      # The player begins the game in the center of the screen, not moving in any direction.
      state.player ||= state.new_entity(:player, { x: 640,
                                                 y: 360,
                                                 attack_angle: 0,
                                                 dx: 0,
                                                 dy: 0 })
    end
  
    # Outputs a gray background.
    # Calls the methods needed to output the player, zombies, etc onto the screen.
    def render
      outputs.solids << [grid.rect, 100, 100, 100]
      render_zombies
      render_killed_zombies
      render_player
      render_flash
    end
  
    # Outputs the zombies on the screen and sets values for the sprites, such as the position, width, height, and animation.
    def render_zombies
      outputs.sprites << state.zombies.map do |z| # performs action on all zombies in the collection
        z.sprite = [z.x, z.y, 4 * 3, 8 * 3, animation_sprite(z)].sprite # sets definition for sprite, calls animation_sprite method
        z.sprite
      end
    end
  
    # Outputs sprites of killed zombies, and displays a slash image to show that a zombie has been killed.
    def render_killed_zombies
      outputs.sprites << state.killed_zombies.map do |z| # performs action on all killed zombies in collection
        z.sprite = [z.x,
                    z.y,
                    4 * 3,
                    8 * 3,
                    animation_sprite(z, z.death_at), # calls animation_sprite method
                    0, # angle
                    255 * z.death_at.ease(30, :flip)].sprite # transparency of a zombie changes when they die
                    # change the value of 30 and see what happens when a zombie is killed
  
        # Sets values to output the slash over the zombie's sprite when a zombie is killed.
        # The slash is tilted 45 degrees from the angle of the player's attack.
        # Change the 3 inside scale_rect to 30 and the slash will be HUGE! Scale_rect positions
        # the slash over the killed zombie's sprite.
        [z.sprite, [z.sprite.rect, 'sprites/slash.png', 45 + state.player.attack_angle_on_click, z.sprite.a].scale_rect(3, 0.5, 0.5)]
      end
    end
  
    # Outputs the player sprite using the images in the sprites folder.
    def render_player
      state.player_sprite = [state.player.x,
                             state.player.y,
                            4 * 3,
                            8 * 3, "sprites/player-#{animation_index(state.player.created_at_elapsed)}.png"] # string interpolation
      outputs.sprites << state.player_sprite
  
      # Outputs a small red square that previews the angles that the player can attack in.
      # It can be moved in a perfect circle around the player to show possible movements.
      # Change the 60 in the parenthesis and see what happens to the movement of the red square.
      outputs.solids <<  [state.player.x + state.player.attack_angle.vector_x(60),
                          state.player.y + state.player.attack_angle.vector_y(60),
                          3, 3, 255, 0, 0]
    end
  
    # Renders flash as a solid. The screen turns white for 10 frames when a zombie is killed.
    def render_flash
      return if state.flash_at.elapsed_time > 10 # return if more than 10 frames have passed since flash.
      # Transparency gradually changes (or eases) during the 10 frames of flash.
      outputs.primitives << [grid.rect, 255, 255, 255, 255 * state.flash_at.ease(10, :flip)].solid
    end
  
    # Calls all methods necessary for performing calculations.
    def calc
      calc_spawn_zombie
      calc_move_zombies
      calc_player
      calc_kill_zombie
    end
  
    # Decreases the zombie spawn countdown by 1 if it has a value greater than 0.
    def calc_spawn_zombie
      if state.zombie_spawn_countdown > 0
        state.zombie_spawn_countdown -= 1
        return
      end
  
      # New zombies are created, positioned on the screen, and added to the zombies collection.
      state.zombies << state.new_entity(:zombie) do |z| # each zombie is declared a new entity
        if rand > 0.5
          z.x = grid.rect.w.randomize(:ratio) # random x position on screen (within grid scope)
          z.y = [-10, 730].sample # y position is set to either -10 or 730 (randomly chosen)
          # the possible values exceed the screen's scope so zombies appear to be coming from far away
        else
          z.x = [-10, 1290].sample # x position is set to either -10 or 1290 (randomly chosen)
          z.y = grid.rect.w.randomize(:ratio) # random y position on screen
        end
      end
  
      # Calls random_spawn_countdown method (determines how fast new zombies appear)
      state.zombie_spawn_countdown = random_spawn_countdown state.zombie_min_spawn_rate
      state.zombie_min_spawn_rate -= 1
      # set to either the current zombie_min_spawn_rate or 0, depending on which value is greater
      state.zombie_min_spawn_rate  = state.zombie_min_spawn_rate.greater(0)
    end
  
    # Moves all zombies towards the center of the screen.
    # All zombies that reach the center (640, 360) are rejected from the zombies collection and disappear.
    def calc_move_zombies
      state.zombies.each do |z| # for each zombie in the collection
        z.y = z.y.towards(360, 0.1) # move the zombie towards the center (640, 360) at a rate of 0.1
        z.x = z.x.towards(640, 0.1) # change 0.1 to 1.1 and see how much faster the zombies move to the center
      end
      state.zombies = state.zombies.reject { |z| z.y == 360 && z.x == 640 } # remove zombies that are in center
    end
  
    # Calculates the position and movement of the player on the screen.
    def calc_player
      state.player.x += state.player.dx # changes x based on dx (change in x)
      state.player.y += state.player.dy # changes y based on dy (change in y)
  
      state.player.dx *= 0.9 # scales dx down
      state.player.dy *= 0.9 # scales dy down
  
      # Compares player's x to 1280 to find lesser value, then compares result to 0 to find greater value.
      # This ensures that the player remains within the screen's scope.
      state.player.x = state.player.x.lesser(1280).greater(0)
      state.player.y = state.player.y.lesser(720).greater(0) # same with player's y
    end
  
    # Finds all zombies that intersect with the player's sprite. These zombies are removed from the zombies collection
    # and added to the killed_zombies collection since any zombie that intersects with the player is killed.
    def calc_kill_zombie
  
      # Find all zombies that intersect with the player. They are considered killed.
      killed_this_frame = state.zombies.find_all { |z| z.sprite && (z.sprite.intersect_rect? state.player_sprite) }
      state.zombies = state.zombies - killed_this_frame # remove newly killed zombies from zombies collection
      state.killed_zombies += killed_this_frame # add newly killed zombies to killed zombies
  
      if killed_this_frame.length > 0 # if atleast one zombie was killed in the frame
        state.flash_at = state.tick_count # flash_at set to the frame when the zombie was killed
      # Don't forget, the rendered flash lasts for 10 frames after the zombie is killed (look at render_flash method)
      end
  
      # Sets the tick_count (passage of time) as the value of the death_at variable for each killed zombie.
      # Death_at stores the frame a zombie was killed.
      killed_this_frame.each do |z|
        z.death_at = state.tick_count
      end
  
      # Zombies are rejected from the killed_zombies collection depending on when they were killed.
      # They are rejected if more than 30 frames have passed since their death.
      state.killed_zombies = state.killed_zombies.reject { |z| state.tick_count - z.death_at > 30 }
    end
  
    # Uses input from the user to move the player around the screen.
    def input
  
      # If the "a" key or left key is pressed, the x position of the player decreases.
      # Otherwise, if the "d" key or right key is pressed, the x position of the player increases.
      if inputs.keyboard.key_held.a || inputs.keyboard.key_held.left
        state.player.x -= 5
      elsif inputs.keyboard.key_held.d || inputs.keyboard.key_held.right
        state.player.x += 5
      end
  
      # If the "w" or up key is pressed, the y position of the player increases.
      # Otherwise, if the "s" or down key is pressed, the y position of the player decreases.
      if inputs.keyboard.key_held.w || inputs.keyboard.key_held.up
        state.player.y += 5
      elsif inputs.keyboard.key_held.s || inputs.keyboard.key_held.down
        state.player.y -= 5
      end
  
      # Sets the attack angle so the player can move and attack in the precise direction it wants to go.
      # If the mouse is moved, the attack angle is changed (based on the player's position and mouse position).
      # Attack angle also contributes to the position of red square.
      if inputs.mouse.moved
        state.player.attack_angle = inputs.mouse.position.angle_from [state.player.x, state.player.y]
      end
  
      if inputs.mouse.click && state.player.dx < 0.5 && state.player.dy < 0.5
        state.player.attack_angle_on_click = inputs.mouse.position.angle_from [state.player.x, state.player.y]
        state.player.attack_angle = state.player.attack_angle_on_click # player's attack angle is set
        state.player.dx = state.player.attack_angle.vector_x(25) # change in player's position
        state.player.dy = state.player.attack_angle.vector_y(25)
      end
    end
  
    # Sets the zombie spawn's countdown to a random number.
    # How fast zombies appear (change the 60 to 6 and too many zombies will appear at once!)
    def random_spawn_countdown minimum
      10.randomize(:ratio, :sign).to_i + 60
    end
  
    # Helps to iterate through the images in the sprites folder by setting the animation index.
    # 3 frames is how long to show an image, and 6 is how many images to flip through.
    def animation_index at
      at.idiv(3).mod(6)
    end
  
    # Animates the zombies by using the animation index to go through the images in the sprites folder.
    def animation_sprite zombie, at = nil
      at ||= zombie.created_at_elapsed # how long it is has been since a zombie was created
      index = animation_index at
      "sprites/zombie-#{index}.png" # string interpolation to iterate through images
    end
  end
  
  $protect_the_puppies_from_the_zombies = ProtectThePuppiesFromTheZombies.new
  
  def tick args
    $protect_the_puppies_from_the_zombies.grid    = args.grid
    $protect_the_puppies_from_the_zombies.inputs  = args.inputs
    $protect_the_puppies_from_the_zombies.state    = args.state
    $protect_the_puppies_from_the_zombies.outputs = args.outputs
    $protect_the_puppies_from_the_zombies.tick
    tick_instructions args, "How to get the mouse position and translate it to an x, y position using .vector_x and .vector_y. CLICK to play."
  end
  
  def tick_instructions args, text, y = 715
    return if args.state.key_event_occurred
    if args.inputs.mouse.click ||
       args.inputs.keyboard.directional_vector ||
       args.inputs.keyboard.key_down.enter ||
       args.inputs.keyboard.key_down.escape
      args.state.key_event_occurred = true
    end
  
    args.outputs.debug << [0, y - 50, 1280, 60].solid
    args.outputs.debug << [640, y, text, 1, 1, 255, 255, 255].label
    args.outputs.debug << [640, y - 25, "(click to dismiss instructions)" , -2, 1, 255, 255, 255].label
  end

#+end_src

*** Mouse - Mouse Move Paint App - main.rb
#+begin_src ruby
  # ./samples/05_mouse/03_mouse_move_paint_app/app/main.rb
  =begin
  
   APIs listing that haven't been encountered in previous sample apps:
  
   - Floor: Method that returns an integer number smaller than or equal to the original with no decimal.
  
     For example, if we have a variable, a = 13.7, and we called floor on it, it would look like this...
     puts a.floor()
     which would print out 13.
     (There is also a ceil method, which returns an integer number greater than or equal to the original
     with no decimal. If we had called ceil on the variable a, the result would have been 14.)
  
   Reminders:
  
   - Hashes: Collection of unique keys and their corresponding values. The value can be found
     using their keys.
  
     For example, if we have a "numbers" hash that stores numbers in English as the
     key and numbers in Spanish as the value, we'd have a hash that looks like this...
     numbers = { "one" => "uno", "two" => "dos", "three" => "tres" }
     and on it goes.
  
     Now if we wanted to find the corresponding value of the "one" key, we could say
     puts numbers["one"]
     which would print "uno" to the console.
  
   - args.state.new_entity: Used when we want to create a new object, like a sprite or button.
     In this sample app, new_entity is used to create a new button that clears the grid.
     (Remember, you can use state to define ANY property and it will be retained across frames.)
  
   - args.inputs.mouse.click.point.(x|y): The x and y location of the mouse.
  
   - args.inputs.mouse.click.point.created_at: The frame the mouse click occurred in.
  
   - args.outputs.labels: An array. The values in the array generate a label.
     The parameters are [X, Y, TEXT, SIZE, ALIGN, RED, GREEN, BLUE, ALPHA, FONT STYLE]
     For more information about labels, go to mygame/documentation/02-labels.md.
  
   - ARRAY#inside_rect?: Returns true or false depending on if the point is inside the rect.
  
  =end
  
  # This sample app shows an empty grid that the user can paint on.
  # To paint, the user must keep their mouse presssed and drag it around the grid.
  # The "clear" button allows users to clear the grid so they can start over.
  
  class PaintApp
    attr_accessor :inputs, :state, :outputs, :grid, :args
  
    # Runs methods necessary for the game to function properly.
    def tick
      print_title
      add_grid
      check_click
      draw_buttons
    end
  
    # Prints the title onto the screen by using a label.
    # Also separates the title from the grid with a line as a horizontal separator.
    def print_title
      args.outputs.labels << [ 640, 700, 'Paint!', 0, 1 ]
      outputs.lines << horizontal_separator(660, 0, 1280)
    end
  
    # Sets the starting position, ending position, and color for the horizontal separator.
    # The starting and ending positions have the same y values.
    def horizontal_separator y, x, x2
      [x, y, x2, y, 150, 150, 150]
    end
  
    # Sets the starting position, ending position, and color for the vertical separator.
    # The starting and ending positions have the same x values.
    def vertical_separator x, y, y2
      [x, y, x, y2, 150, 150, 150]
    end
  
    # Outputs a border and a grid containing empty squares onto the screen.
    def add_grid
  
      # Sets the x, y, height, and width of the grid.
      # There are 31 horizontal lines and 31 vertical lines in the grid.
      # Feel free to count them yourself before continuing!
      x, y, h, w = 640 - 500/2, 640 - 500, 500, 500 # calculations done so the grid appears in screen's center
      lines_h = 31
      lines_v = 31
  
      # Sets values for the grid's border, grid lines, and filled squares.
      # The filled_squares variable is initially set to an empty array.
      state.grid_border ||= [ x, y, h, w ] # definition of grid's outer border
      state.grid_lines ||= draw_grid(x, y, h, w, lines_h, lines_v) # calls draw_grid method
      state.filled_squares ||= [] # there are no filled squares until the user fills them in
  
      # Outputs the grid lines, border, and filled squares onto the screen.
      outputs.lines.concat state.grid_lines
      outputs.borders << state.grid_border
      outputs.solids << state.filled_squares
    end
  
    # Draws the grid by adding in vertical and horizontal separators.
    def draw_grid x, y, h, w, lines_h, lines_v
  
      # The grid starts off empty.
      grid = []
  
      # Calculates the placement and adds horizontal lines or separators into the grid.
      curr_y = y # start at the bottom of the box
      dist_y = h / (lines_h + 1) # finds distance to place horizontal lines evenly throughout 500 height of grid
      lines_h.times do
        curr_y += dist_y # increment curr_y by the distance between the horizontal lines
        grid << horizontal_separator(curr_y, x, x + w - 1) # add a separator into the grid
      end
  
      # Calculates the placement and adds vertical lines or separators into the grid.
      curr_x = x # now start at the left of the box
      dist_x = w / (lines_v + 1) # finds distance to place vertical lines evenly throughout 500 width of grid
      lines_v.times do
        curr_x += dist_x # increment curr_x by the distance between the vertical lines
        grid << vertical_separator(curr_x, y + 1, y  + h) # add separator
      end
  
      # paint_grid uses a hash to assign values to keys.
      state.paint_grid ||= {"x" => x, "y" => y, "h" => h, "w" => w, "lines_h" => lines_h,
                            "lines_v" => lines_v, "dist_x" => dist_x,
                            "dist_y" => dist_y }
  
      return grid
    end
  
    # Checks if the user is keeping the mouse pressed down and sets the mouse_hold variable accordingly using boolean values.
    # If the mouse is up, the user cannot drag the mouse.
    def check_click
      if inputs.mouse.down #is mouse up or down?
        state.mouse_held = true # mouse is being held down
      elsif inputs.mouse.up # if mouse is up
      state.mouse_held = false # mouse is not being held down or dragged
        state.mouse_dragging = false
      end
  
      if state.mouse_held &&    # mouse needs to be down
        !inputs.mouse.click &&     # must not be first click
        ((inputs.mouse.previous_click.point.x - inputs.mouse.position.x).abs > 15) # Need to move 15 pixels before "drag"
        state.mouse_dragging = true
      end
  
      # If the user clicks their mouse inside the grid, the search_lines method is called with a click input type.
      if ((inputs.mouse.click) && (inputs.mouse.click.point.inside_rect? state.grid_border))
        search_lines(inputs.mouse.click.point, :click)
  
      # If the user drags their mouse inside the grid, the search_lines method is called with a drag input type.
      elsif ((state.mouse_dragging) && (inputs.mouse.position.inside_rect? state.grid_border))
        search_lines(inputs.mouse.position, :drag)
      end
    end
  
    # Sets the definition of a grid box and handles user input to fill in or clear grid boxes.
    def search_lines (point, input_type)
      point.x -= state.paint_grid["x"] # subtracts the value assigned to the "x" key in the paint_grid hash
      point.y -= state.paint_grid["y"] # subtracts the value assigned to the "y" key in the paint_grid hash
  
      # Remove code following the .floor and see what happens when you try to fill in grid squares
      point.x = (point.x / state.paint_grid["dist_x"]).floor * state.paint_grid["dist_x"]
      point.y = (point.y / state.paint_grid["dist_y"]).floor * state.paint_grid["dist_y"]
  
      point.x += state.paint_grid["x"]
      point.y += state.paint_grid["y"]
  
      # Sets definition of a grid box, meaning its x, y, width, and height.
      # Floor is called on the point.x and point.y variables.
      # Ceil method is called on values of the distance hash keys, setting the width and height of a box.
      grid_box = [ point.x.floor, point.y.floor, state.paint_grid["dist_x"].ceil, state.paint_grid["dist_y"].ceil ]
  
      if input_type == :click # if user clicks their mouse
        if state.filled_squares.include? grid_box # if grid box is already filled in
          state.filled_squares.delete grid_box # box is cleared and removed from filled_squares
        else
          state.filled_squares << grid_box # otherwise, box is filled in and added to filled_squares
        end
      elsif input_type == :drag # if user drags mouse
        unless state.filled_squares.include? grid_box # unless the grid box dragged over is already filled in
          state.filled_squares << grid_box # the box is filled in and added to filled_squares
        end
      end
    end
  
    # Creates and outputs a "Clear" button on the screen using a label and a border.
    # If the button is clicked, the filled squares are cleared, making the filled_squares collection empty.
    def draw_buttons
      x, y, w, h = 390, 50, 240, 50
      state.clear_button        ||= state.new_entity(:button_with_fade)
  
      # The x and y positions are set to display the label in the center of the button.
      # Try changing the first two parameters to simply x, y and see what happens to the text placement!
      state.clear_button.label  ||= [x + w.half, y + h.half + 10, "Clear", 0, 1] # placed in center of border
      state.clear_button.border ||= [x, y, w, h]
  
      # If the mouse is clicked inside the borders of the clear button,
      # the filled_squares collection is emptied and the squares are cleared.
      if inputs.mouse.click && inputs.mouse.click.point.inside_rect?(state.clear_button.border)
        state.clear_button.clicked_at = inputs.mouse.click.created_at # time (frame) the click occurred
        state.filled_squares.clear
        inputs.mouse.previous_click = nil
      end
  
      outputs.labels << state.clear_button.label
      outputs.borders << state.clear_button.border
  
      # When the clear button is clicked, the color of the button changes
      # and the transparency changes, as well. If you change the time from
      # 0.25.seconds to 1.25.seconds or more, the change will last longer.
      if state.clear_button.clicked_at
        outputs.solids << [x, y, w, h, 0, 180, 80, 255 * state.clear_button.clicked_at.ease(0.25.seconds, :flip)]
      end
    end
  end
  
  $paint_app = PaintApp.new
  
  def tick args
    $paint_app.inputs = args.inputs
    $paint_app.state = args.state
    $paint_app.grid = args.grid
    $paint_app.args = args
    $paint_app.outputs = args.outputs
    $paint_app.tick
    tick_instructions args, "How to create a simple paint app. CLICK and HOLD to draw."
  end
  
  def tick_instructions args, text, y = 715
    return if args.state.key_event_occurred
    if args.inputs.mouse.click ||
       args.inputs.keyboard.directional_vector ||
       args.inputs.keyboard.key_down.enter ||
       args.inputs.keyboard.key_down.escape
      args.state.key_event_occurred = true
    end
  
    args.outputs.debug << [0, y - 50, 1280, 60].solid
    args.outputs.debug << [640, y, text, 1, 1, 255, 255, 255].label
    args.outputs.debug << [640, y - 25, "(click to dismiss instructions)" , -2, 1, 255, 255, 255].label
  end

#+end_src

*** Mouse - Coordinate Systems - main.rb
#+begin_src ruby
  # ./samples/05_mouse/04_coordinate_systems/app/main.rb
  =begin
  
   APIs listing that haven't been encountered in previous sample apps:
  
   - args.inputs.mouse.click.position: Coordinates of the mouse's position on the screen.
     Unlike args.inputs.mouse.click.point, the mouse does not need to be pressed down for
     position to know the mouse's coordinates.
     For more information about the mouse, go to mygame/documentation/07-mouse.md.
  
   Reminders:
  
   - args.inputs.mouse.click: This property will be set if the mouse was clicked.
  
   - args.inputs.mouse.click.point.(x|y): The x and y location of the mouse.
  
   - String interpolation: Uses #{} syntax; everything between the #{ and the } is evaluated
     as Ruby code, and the placeholder is replaced with its corresponding value or result.
  
     In this sample app, string interpolation is used to show the current position of the mouse
     in a label.
  
   - args.outputs.labels: An array that generates a label.
     The parameters are [X, Y, TEXT, SIZE, ALIGN, RED, GREEN, BLUE, ALPHA, FONT STYLE]
     For more information about labels, go to mygame/documentation/02-labels.md.
  
   - args.outputs.solids: An array that generates a solid.
     The parameters are [X, Y, WIDTH, HEIGHT, RED, GREEN, BLUE, ALPHA]
     For more information about solids, go to mygame/documentation/03-solids-and-borders.md.
  
   - args.outputs.lines: An array that generates a line.
     The parameters are [X, Y, X2, Y2, RED, GREEN, BLUE, ALPHA]
     For more information about lines, go to mygame/documentation/04-lines.md.
  
  =end
  
  # This sample app shows a coordinate system or grid. The user can move their mouse around the screen and the
  # coordinates of their position on the screen will be displayed. Users can choose to view one quadrant or
  # four quadrants by pressing the button.
  
  def tick args
  
    # The addition and subtraction in the first two parameters of the label and solid
    # ensure that the outputs don't overlap each other. Try removing them and see what happens.
    pos = args.inputs.mouse.position # stores coordinates of mouse's position
    args.outputs.labels << [pos.x + 10, pos.y + 10, "#{pos}"] # outputs label of coordinates
    args.outputs.solids << [pos.x -  2, pos.y - 2, 5, 5] # outputs small blackk box placed where mouse is hovering
  
    button = [0, 0, 370, 50] # sets definition of toggle button
    args.outputs.borders << button # outputs button as border (not filled in)
    args.outputs.labels << [10, 35, "click here toggle coordinate system"] # label of button
    args.outputs.lines << [    0, -720,    0, 720] # vertical line dividing quadrants
    args.outputs.lines << [-1280,    0, 1280,   0] # horizontal line dividing quadrants
  
    if args.inputs.mouse.click # if the user clicks the mouse
      pos = args.inputs.mouse.click.point # pos's value is point where user clicked (coordinates)
      if pos.inside_rect? button # if the click occurred inside the button
        if args.grid.name == :bottom_left # if the grid shows bottom left as origin
          args.grid.origin_center! # origin will be shown in center
        else
          args.grid.origin_bottom_left! # otherwise, the view will change to show bottom left as origin
        end
      end
    end
  
    tick_instructions args, "Sample app shows the two supported coordinate systems in Game Toolkit."
  end
  
  def tick_instructions args, text, y = 715
    return if args.state.key_event_occurred
    if args.inputs.mouse.click ||
       args.inputs.keyboard.directional_vector ||
       args.inputs.keyboard.key_down.enter ||
       args.inputs.keyboard.key_down.escape
      args.state.key_event_occurred = true
    end
  
    args.outputs.debug << [0, y - 50, 1280, 60].solid
    args.outputs.debug << [640, y, text, 1, 1, 255, 255, 255].label
    args.outputs.debug << [640, y - 25, "(click to dismiss instructions)" , -2, 1, 255, 255, 255].label
  end

#+end_src

*** Save Load - Save Load Game - main.rb
#+begin_src ruby
  # ./samples/06_save_load/01_save_load_game/app/main.rb
  =begin
  
   APIs listing that haven't been encountered in previous sample apps:
  
   - Symbol (:): Ruby object with a name and an internal ID. Symbols are useful
     because with a given symbol name, you can refer to the same object throughout
     a Ruby program.
  
     In this sample app, we're using symbols for our buttons. We have buttons that
     light fires, save, load, etc. Each of these buttons has a distinct symbol like
     :light_fire, :save_game, :load_game, etc.
  
   - to_sym: Returns the symbol corresponding to the given string; creates the symbol
     if it does not already exist.
     For example,
     'car'.to_sym
     would return the symbol :car.
  
   - last: Returns the last element of an array.
  
   Reminders:
  
   - num1.lesser(num2): finds the lower value of the given options.
     For example, in the statement
     a = 4.lesser(3)
     3 has a lower value than 4, which means that the value of a would be set to 3,
     but if the statement had been
     a = 4.lesser(5)
     4 has a lower value than 5, which means that the value of a would be set to 4.
  
   - num1.fdiv(num2): returns the float division (will have a decimal) of the two given numbers.
     For example, 5.fdiv(2) = 2.5 and 5.fdiv(5) = 1.0
  
   - String interpolation: uses #{} syntax; everything between the #{ and the } is evaluated
     as Ruby code, and the placeholder is replaced with its corresponding value or result.
  
   - args.outputs.labels: An array. Values generate a label.
     Parameters are [X, Y, TEXT, SIZE, ALIGN, RED, GREEN, BLUE, ALPHA, FONT STYLE]
     For more information, go to mygame/documentation/02-labels.md.
  
   - ARRAY#inside_rect?: An array with at least two values is considered a point. An array
     with at least four values is considered a rect. The inside_rect? function returns true
     or false depending on if the point is inside the rect.
  
  =end
  
  # This code allows users to perform different tasks, such as saving and loading the game.
  # Users also have options to reset the game and light a fire.
  
  class TextedBasedGame
  
    # Contains methods needed for game to run properly.
    # Increments tick count by 1 each time it runs (60 times in a single second)
    def tick
      default
      show_intro
      state.engine_tick_count += 1
      tick_fire
    end
  
    # Sets default values.
    # The ||= ensures that a variable's value is only set to the value following the = sign
    # if the value has not already been set before. Intialization happens only in the first frame.
    def default
      state.engine_tick_count ||= 0
      state.active_module     ||= :room
      state.fire_progress     ||= 0
      state.fire_ready_in     ||= 10
      state.previous_fire     ||= :dead
      state.fire              ||= :dead
    end
  
    def show_intro
      return unless state.engine_tick_count == 0 # return unless the game just started
      set_story_line "awake." # calls set_story_line method, sets to "awake"
    end
  
    # Sets story line.
    def set_story_line story_line
      state.story_line    = story_line # story line set to value of parameter
      state.active_module = :alert # active module set to alert
    end
  
    # Clears story line.
    def clear_storyline
      state.active_module = :none # active module set to none
      state.story_line = nil # story line is cleared, set to nil (or empty)
    end
  
    # Determines fire progress (how close the fire is to being ready to light).
    def tick_fire
      return if state.active_module == :alert # return if active module is alert
      state.fire_progress += 1 # increment fire progress
      # fire_ready_in is 10. The fire_progress is either the current value or 10, whichever has a lower value.
      state.fire_progress = state.fire_progress.lesser(state.fire_ready_in)
    end
  
    # Sets the value of fire (whether it is dead or roaring), and the story line
    def light_fire
      return unless fire_ready? # returns unless the fire is ready to be lit
      state.fire = :roaring # fire is lit, set to roaring
      state.fire_progress = 0 # the fire progress returns to 0, since the fire has been lit
      if state.fire != state.previous_fire
        set_story_line "the fire is #{state.fire}." # the story line is set using string interpolation
        state.previous_fire = state.fire
      end
    end
  
    # Checks if the fire is ready to be lit. Returns a boolean value.
    def fire_ready?
      # If fire_progress (value between 0 and 10) is equal to fire_ready_in (value of 10),
      # the fire is ready to be lit.
      state.fire_progress == state.fire_ready_in
    end
  
    # Divides the value of the fire_progress variable by 10 to determine how close the user is to
    # being able to light a fire.
    def light_fire_progress
      state.fire_progress.fdiv(10) # float division
    end
  
    # Defines fire as the state.fire variable.
    def fire
      state.fire
    end
  
    # Sets the title of the room.
    def room_title
      return "a room that is dark" if state.fire == :dead # room is dark if the fire is dead
      return "a room that is lit" # room is lit if the fire is not dead
    end
  
    # Sets the active_module to room.
    def go_to_room
      state.active_module = :room
    end
  
    # Defines active_module as the state.active_module variable.
    def active_module
      state.active_module
    end
  
    # Defines story_line as the state.story_line variable.
    def story_line
      state.story_line
    end
  
    # Update every 60 frames (or every second)
    def should_tick?
      state.tick_count.mod_zero?(60)
    end
  
    # Sets the value of the game state provider.
    def initialize game_state_provider
      @game_state_provider = game_state_provider
    end
  
    # Defines the game state.
    # Any variable prefixed with an @ symbol is an instance variable.
    def state
      @game_state_provider.state
    end
  
    # Saves the state of the game in a text file called game_state.txt.
    def save
      $gtk.serialize_state('game_state.txt', state)
    end
  
    # Loads the game state from the game_state.txt text file.
    # If the load is unsuccessful, the user is informed since the story line indicates the failure.
    def load
      parsed_state = $gtk.deserialize_state('game_state.txt')
      if !parsed_state
        set_story_line "no game to load. press save first."
      else
        $gtk.args.state = parsed_state
      end
    end
  
    # Resets the game.
    def reset
      $gtk.reset
    end
  end
  
  class TextedBasedGamePresenter
    attr_accessor :state, :outputs, :inputs
  
    # Creates empty collection called highlights.
    # Calls methods necessary to run the game.
    def tick
      state.layout.highlights ||= []
      game.tick if game.should_tick?
      render
      process_input
    end
  
    # Outputs a label of the tick count (passage of time) and calls all render methods.
    def render
      outputs.labels << [10, 30, state.tick_count]
      render_alert
      render_room
      render_highlights
    end
  
    # Outputs a label onto the screen that shows the story line, and also outputs a "close" button.
    def render_alert
      return unless game.active_module == :alert
  
      outputs.labels << [640, 480, game.story_line, 5, 1]  # outputs story line label
      outputs.primitives << button(:alert_dismiss, 490, 380, "close")  # positions "close" button under story line
    end
  
    def render_room
      return unless game.active_module == :room
      outputs.labels << [640, 700, game.room_title, 4, 1] # outputs room title label at top of screen
  
      # The parameters for these outputs are (symbol, x, y, text, value/percentage) and each has a y value
      # that positions it 60 pixels lower than the previous output.
  
      # outputs the light_fire_progress bar, uses light_fire_progress for its percentage (which changes bar's appearance)
      outputs.primitives << progress_bar(:light_fire, 490, 600, "light fire", game.light_fire_progress)
      outputs.primitives << button(       :save_game, 490, 540, "save") # outputs save button
      outputs.primitives << button(       :load_game, 490, 480, "load") # outputs load button
      outputs.primitives << button(      :reset_game, 490, 420, "reset") # outputs reset button
      outputs.labels << [640, 30, "the fire is #{game.fire}", 0, 1] # outputs fire label at bottom of screen
    end
  
    # Outputs a collection of highlights using an array to set their values, and also rejects certain values from the collection.
    def render_highlights
      state.layout.highlights.each do |h| # for each highlight in the collection
          h.lifetime -= 1 # decrease the value of its lifetime
        end
  
        outputs.solids << state.layout.highlights.map do |h| # outputs highlights collection
          [h.x, h.y, h.w, h.h, h.color, 255 * h.lifetime / h.max_lifetime] # sets definition for each highlight
          # transparency changes; divide lifetime by max_lifetime, multiply result by 255
        end
  
        # reject highlights from collection that have no remaining lifetime
        state.layout.highlights = state.layout.highlights.reject { |h| h.lifetime <= 0 }
    end
  
    # Checks whether or not a button was clicked.
    # Returns a boolean value.
    def process_input
      button = button_clicked? # calls button_clicked? method
    end
  
    # Returns a boolean value.
    # Finds the button that was clicked from the button list and determines what method to call.
    # Adds a highlight to the highlights collection.
    def button_clicked?
      return nil unless click_pos # return nil unless click_pos holds coordinates of mouse click
        button = @button_list.find do |k, v| # goes through button_list to find button clicked
          click_pos.inside_rect? v[:primitives].last.rect # was the mouse clicked inside the rect of button?
        end
        return unless button # return unless a button was clicked
        method_to_call = "#{button[0]}_clicked".to_sym # sets method_to_call to symbol (like :save_game or :load_game)
        if self.respond_to? method_to_call # returns true if self responds to the given method (method actually exists)
          border = button[1][:primitives].last # sets border definition using value of last key in button list hash
  
          # declares each highlight as a new entity, sets properties
          state.layout.highlights << state.new_entity(:highlight) do |h|
              h.x = border.x
              h.y = border.y
              h.w = border.w
              h.h = border.h
              h.max_lifetime = 10
              h.lifetime = h.max_lifetime
              h.color = [120, 120, 180] # sets color to shade of purple
            end
  
            self.send method_to_call # invoke method identified by symbol
          else # otherwise, if self doesn't respond to given method
            border = button[1][:primitives].last # sets border definition using value of last key in hash
  
            # declares each highlight as a new entity, sets properties
            state.layout.highlights << state.new_entity(:highlight) do |h|
              h.x = border.x
              h.y = border.y
              h.w = border.w
              h.h = border.h
              h.max_lifetime = 4 # different max_lifetime than the one set if respond_to? had been true
              h.lifetime = h.max_lifetime
              h.color = [120, 80, 80] # sets color to dark color
            end
  
            # instructions for users on how to add the missing method_to_call to the code
            puts "It looks like #{method_to_call} doesn't exists on TextedBasedGamePresenter. Please add this method:"
            puts "Just copy the code below and put it in the #{TextedBasedGamePresenter} class definition."
            puts ""
            puts "```"
            puts "class TextedBasedGamePresenter <--- find this class and put the method below in it"
            puts ""
            puts "  def #{method_to_call}"
            puts "    puts 'Yay that worked!'"
            puts "  end"
            puts ""
            puts "end <-- make sure to put the #{method_to_call} method in between the `class` word and the final `end` statement."
            puts "```"
            puts ""
        end
    end
  
    # Returns the position of the mouse when it is clicked.
    def click_pos
      return nil unless inputs.mouse.click # returns nil unless the mouse was clicked
      return inputs.mouse.click.point # returns location of mouse click (coordinates)
    end
  
    # Creates buttons for the button_list and sets their values using a hash (uses symbols as keys)
    def button id, x, y, text
      @button_list[id] ||= { # assigns values to hash keys
        id: id,
        text: text,
        primitives: [
          [x + 10, y + 30, text, 2, 0].label, # positions label inside border
          [x, y, 300, 50].border,             # sets definition of border
        ]
      }
  
      @button_list[id][:primitives] # returns label and border for buttons
    end
  
    # Creates a progress bar (used for lighting the fire) and sets its values.
    def progress_bar id, x, y, text, percentage
      @button_list[id] = { # assigns values to hash keys
        id: id,
        text: text,
        primitives: [
          [x, y, 300, 50, 100, 100, 100].solid, # sets definition for solid (which fills the bar with gray)
          [x + 10, y + 30, text, 2, 0].label, # sets definition for label, positions inside border
          [x, y, 300, 50].border, # sets definition of border
        ]
      }
  
      # Fills progress bar based on percentage. If the fire was ready to be lit (100%) and we multiplied by
      # 100, only 1/3 of the bar would only be filled in. 200 would cause only 2/3 to be filled in.
      @button_list[id][:primitives][0][2] = 300 * percentage
      @button_list[id][:primitives]
    end
  
    # Defines the game.
    def game
      @game
    end
  
    # Initalizes the game and creates an empty list of buttons.
    def initialize
      @game = TextedBasedGame.new self
      @button_list ||= {}
    end
  
    # Clears the storyline and takes the user to the room.
    def alert_dismiss_clicked
      game.clear_storyline
      game.go_to_room
    end
  
    # Lights the fire when the user clicks the "light fire" option.
    def light_fire_clicked
      game.light_fire
    end
  
    # Saves the game when the user clicks the "save" option.
    def save_game_clicked
      game.save
    end
  
    # Resets the game when the user clicks the "reset" option.
    def reset_game_clicked
      game.reset
    end
  
    # Loads the game when the user clicks the "load" option.
    def load_game_clicked
      game.load
    end
  end
  
  $text_based_rpg = TextedBasedGamePresenter.new
  
  def tick args
    $text_based_rpg.state = args.state
    $text_based_rpg.outputs = args.outputs
    $text_based_rpg.inputs = args.inputs
    $text_based_rpg.tick
  end

#+end_src

*** Advanced Audio - Audio Mixer - main.rb
#+begin_src ruby
  # ./samples/07_advanced_audio/01_audio_mixer/app/main.rb
  # these are the properties that you can sent on args.audio
  def spawn_new_sound args, name, path
    # Spawn randomly in an area that won't be covered by UI.
    screenx = (rand * 600.0) + 200.0
    screeny = (rand * 400.0) + 100.0
  
    id = new_sound_id! args
    # you can hang anything on the audio hashes you want, so we store the
    #  actual screen position in here for convenience.
    args.audio[id] = {
      name: name,
      input: path,
      screenx: screenx,
      screeny: screeny,
      x: ((screenx / 1279.0) * 2.0) - 1.0,  # scale to -1.0 - 1.0 range
      y: ((screeny / 719.0) * 2.0) - 1.0,   # scale to -1.0 - 1.0 range
      z: 0.0,
      gain: 1.0,
      pitch: 1.0,
      looping: true,
      paused: false
    }
  
    args.state.selected = id
  end
  
  # these are values you can change on the ~args.audio~ data structure
  def input_panel args
    return unless args.state.panel
    return if args.state.dragging
  
    audio_entry = args.audio[args.state.selected]
    results = args.state.panel
  
    if args.state.mouse_state == :held && args.inputs.mouse.position.inside_rect?(results.pitch_slider_rect.rect)
      audio_entry.pitch = 2.0 * ((args.inputs.mouse.x - results.pitch_slider_rect.x).to_f / (results.pitch_slider_rect.w - 1.0))
    elsif args.state.mouse_state == :held && args.inputs.mouse.position.inside_rect?(results.playtime_slider_rect.rect)
      audio_entry.playtime = audio_entry.length_ * ((args.inputs.mouse.x - results.playtime_slider_rect.x).to_f / (results.playtime_slider_rect.w - 1.0))
    elsif args.state.mouse_state == :held && args.inputs.mouse.position.inside_rect?(results.gain_slider_rect.rect)
      audio_entry.gain = (args.inputs.mouse.x - results.gain_slider_rect.x).to_f / (results.gain_slider_rect.w - 1.0)
    elsif args.inputs.mouse.click && args.inputs.mouse.position.inside_rect?(results.looping_checkbox_rect.rect)
      audio_entry.looping = !audio_entry.looping
    elsif args.inputs.mouse.click && args.inputs.mouse.position.inside_rect?(results.paused_checkbox_rect.rect)
      audio_entry.paused = !audio_entry.paused
    elsif args.inputs.mouse.click && args.inputs.mouse.position.inside_rect?(results.delete_button_rect.rect)
      args.audio.delete args.state.selected
    end
  end
  
  def render_sources args
    args.outputs.primitives << args.audio.keys.map do |k|
      s = args.audio[k]
  
      isselected = (k == args.state.selected)
  
      color = isselected ? [ 0, 255, 0, 255 ] : [ 0, 0, 255, 255 ]
      [
        [s.screenx, s.screeny, args.state.boxsize, args.state.boxsize, *color].solid,
  
        {
          x: s.screenx + args.state.boxsize.half,
          y: s.screeny,
          text: s.name,
          r: 255,
          g: 255,
          b: 255,
          alignment_enum: 1
        }.label!
      ]
    end
  end
  
  def playtime_str t
    return "" unless t
    minutes = (t / 60.0).floor
    seconds = t - (minutes * 60.0).to_f
    return minutes.to_s + ':' + seconds.floor.to_s + ((seconds - seconds.floor).to_s + "000")[1..3]
  end
  
  def label_with_drop_shadow x, y, text
    [
      { x: x + 1, y: y + 1, text: text, vertical_alignment_enum: 1, alignment_enum: 1, r:   0, g:   0, b:   0 }.label!,
      { x: x + 2, y: y + 0, text: text, vertical_alignment_enum: 1, alignment_enum: 1, r:   0, g:   0, b:   0 }.label!,
      { x: x + 0, y: y + 1, text: text, vertical_alignment_enum: 1, alignment_enum: 1, r: 200, g: 200, b: 200 }.label!
    ]
  end
  
  def check_box opts = {}
    checkbox_template = opts.args.layout.rect(w: 0.5, h: 0.5, col: 2)
    final_rect = checkbox_template.center_inside_rect_y(opts.args.layout.rect(row: opts.row, col: opts.col))
    color = { r:   0, g:   0, b:   0 }
    color = { r: 255, g: 255, b: 255 } if opts.checked
  
    {
      rect: final_rect,
      primitives: [
        (final_rect.to_solid color)
      ]
    }
  end
  
  def progress_bar opts = {}
    outer_rect  = opts.args.layout.rect(row: opts.row, col: opts.col, w: 5, h: 1)
    color = opts.percentage * 255
    baseline_progress_bar = opts.args
                                .layout
                                .rect(w: 5, h: 0.5)
  
    final_rect = baseline_progress_bar.center_inside_rect(outer_rect)
    center = final_rect.rect_center_point
  
    {
      rect: final_rect,
      primitives: [
        final_rect.merge(r: color, g: color, b: color, a: 128).solid!,
        label_with_drop_shadow(center.x, center.y, opts.text)
      ]
    }
  end
  
  def panel_primitives args, audio_entry
    results = { primitives: [] }
  
    return results unless audio_entry
  
    # this uses DRGTK's layout apis to layout the controls
    # imagine the screen is split into equal cells (24 cells across, 12 cells up and down)
    # args.layout.rect returns a hash which we merge values with to create primitives
    # using args.layout.rect removes the need for pixel pushing
  
    # args.outputs.debug << args.layout.debug_primitives(r: 255, g: 255, b: 255)
  
    white_color = { r: 255, g: 255, b: 255 }
    label_style = white_color.merge(vertical_alignment_enum: 1)
  
    # panel background
    results.primitives << args.layout.rect(row: 0, col: 0, w: 7, h: 6, include_col_gutter: true, include_row_gutter: true)
                                     .border!(r: 255, g: 255, b: 255)
  
    # title
    results.primitives << args.layout.point(row: 0, col: 3.5, row_anchor: 0.5)
                                     .merge(label_style)
                                     .merge(text:           "Source #{args.state.selected} (#{args.audio[args.state.selected].name})",
                                            size_enum:      3,
                                            alignment_enum: 1)
  
    # seperator line
    results.primitives << args.layout.rect(row: 1, col: 0, w: 7, h: 0)
                                     .line!(white_color)
  
    # screen location
    results.primitives << args.layout.point(row: 1.0, col: 0, row_anchor: 0.5)
                                     .merge(label_style)
                                     .merge(text: "screen:")
  
    results.primitives << args.layout.point(row: 1.0, col: 2, row_anchor: 0.5)
                                     .merge(label_style)
                                     .merge(text: "(#{audio_entry.screenx.to_i}, #{audio_entry.screeny.to_i})")
  
    # position
    results.primitives << args.layout.point(row: 1.5, col: 0, row_anchor: 0.5)
                                     .merge(label_style)
                                     .merge(text: "position:")
  
    results.primitives << args.layout.point(row: 1.5, col: 2, row_anchor: 0.5)
                                     .merge(label_style)
                                     .merge(text: "(#{audio_entry[:x].round(5).to_s[0..6]}, #{audio_entry[:y].round(5).to_s[0..6]})")
  
    results.primitives << args.layout.point(row: 2.0, col: 0, row_anchor: 0.5)
                                     .merge(label_style)
                                     .merge(text: "pitch:")
  
    results.pitch_slider_rect = progress_bar(row: 2.0, col: 2,
                                             percentage: audio_entry.pitch / 2.0,
                                             text: "#{audio_entry.pitch.to_sf}",
                                             args: args)
  
    results.primitives << results.pitch_slider_rect.primitives
  
    results.primitives << args.layout.point(row: 2.5, col: 0, row_anchor: 0.5)
                                     .merge(label_style)
                                     .merge(text: "playtime:")
  
    results.playtime_slider_rect = progress_bar(args: args,
                                                row:  2.5,
                                                col:  2,
                                                percentage: (audio_entry.playtime || 1) / (audio_entry.length_ || 1),
                                                text: "#{playtime_str(audio_entry.playtime)} / #{playtime_str(audio_entry.length_)}")
  
    results.primitives << results.playtime_slider_rect.primitives
  
    results.primitives << args.layout.point(row: 3.0, col: 0, row_anchor: 0.5)
                                     .merge(label_style)
                                     .merge(text: "gain:")
  
    results.gain_slider_rect = progress_bar(args: args,
                                            row:  3.0,
                                            col:  2,
                                            percentage: audio_entry.gain,
                                            text: "#{audio_entry.gain.to_sf}")
  
    results.primitives << results.gain_slider_rect.primitives
  
  
    results.primitives << args.layout.point(row: 3.5, col: 0, row_anchor: 0.5)
                                     .merge(label_style)
                                     .merge(text: "looping:")
  
    checkbox_template = args.layout.rect(w: 0.5, h: 0.5, col: 2)
  
    results.looping_checkbox_rect = check_box(args: args, row: 3.5, col: 2, checked: audio_entry.looping)
    results.primitives << results.looping_checkbox_rect.primitives
  
    results.primitives << args.layout.point(row: 4.0, col: 0, row_anchor: 0.5)
                                     .merge(label_style)
                                     .merge(text: "paused:")
  
    checkbox_template = args.layout.rect(w: 0.5, h: 0.5, col: 2)
  
    results.paused_checkbox_rect = check_box(args: args, row: 4.0, col: 2, checked: !audio_entry.paused)
    results.primitives << results.paused_checkbox_rect.primitives
  
    results.delete_button_rect = { rect: args.layout.rect(row: 5, col: 0, w: 7, h: 1) }
  
    results.primitives << results.delete_button_rect.to_solid(r: 180)
  
    results.primitives << args.layout.point(row: 5, col: 3.5, row_anchor: 0.5)
                                     .merge(label_style)
                                     .merge(text: "DELETE", alignment_enum: 1)
  
    return results
  end
  
  def render_panel args
    args.state.panel = nil
    audio_entry = args.audio[args.state.selected]
    return unless audio_entry
  
    mouse_down = (args.state.mouse_held >= 0)
    args.state.panel = panel_primitives args, audio_entry
    args.outputs.primitives << args.state.panel.primitives
  end
  
  def new_sound_id! args
    args.state.sound_id ||= 0
    args.state.sound_id  += 1
    args.state.sound_id
  end
  
  def render_launcher args
    args.outputs.primitives << args.state.spawn_sound_buttons.map(&:primitives)
  end
  
  def render_ui args
    render_launcher args
    render_panel args
  end
  
  def tick args
    defaults args
    render args
    input args
  end
  
  def input args
    if !args.audio[args.state.selected]
      args.state.selected = nil
      args.state.dragging = nil
    end
  
    # spawn button and node interaction
    if args.inputs.mouse.click
      spawn_sound_button = args.state.spawn_sound_buttons.find { |b| args.inputs.mouse.inside_rect? b.rect }
  
      audio_click_key, audio_click_value = args.audio.find do |k, v|
        args.inputs.mouse.inside_rect? [v.screenx, v.screeny, args.state.boxsize, args.state.boxsize]
      end
  
      if spawn_sound_button
        args.state.selected = nil
        spawn_new_sound args, spawn_sound_button.name, spawn_sound_button.path
      elsif audio_click_key
        args.state.selected = audio_click_key
      end
    end
  
    if args.state.mouse_state == :held && args.state.selected
      v = args.audio[args.state.selected]
      if args.inputs.mouse.inside_rect? [v.screenx, v.screeny, args.state.boxsize, args.state.boxsize]
        args.state.dragging = args.state.selected
      end
  
      if args.state.dragging
        s = args.audio[args.state.selected]
        # you can hang anything on the audio hashes you want, so we store the
        #  actual screen position so it doesn't scale weirdly vs your mouse.
        s.screenx = args.inputs.mouse.x - (args.state.boxsize / 2)
        s.screeny = args.inputs.mouse.y - (args.state.boxsize / 2)
  
        s.screeny = 50 if s.screeny < 50
        s.screeny = (719 - args.state.boxsize) if s.screeny > (719 - args.state.boxsize)
        s.screenx = 0 if s.screenx < 0
        s.screenx = (1279 - args.state.boxsize) if s.screenx > (1279 - args.state.boxsize)
  
        s.x = ((s.screenx / 1279.0) * 2.0) - 1.0  # scale to -1.0 - 1.0 range
        s.y = ((s.screeny / 719.0) * 2.0) - 1.0   # scale to -1.0 - 1.0 range
      end
    elsif args.state.mouse_state == :released
      args.state.dragging = nil
    end
  
    input_panel args
  end
  
  def defaults args
    args.state.mouse_state      ||= :released
    args.state.dragging_source  ||= false
    args.state.selected         ||= 0
    args.state.next_sound_index ||= 0
    args.state.boxsize          ||= 30
    args.state.sound_files      ||= [
      { name: :tada,   path: "sounds/tada.wav"   },
      { name: :splash, path: "sounds/splash.wav" },
      { name: :drum,   path: "sounds/drum.mp3"   },
      { name: :spring, path: "sounds/spring.wav" },
      { name: :music,  path: "sounds/music.ogg"  }
    ]
  
    # generate buttons based off the sound collection above
    args.state.spawn_sound_buttons ||= begin
      # create a group of buttons
      # column centered (using col_offset to calculate the column offset)
      # where each item is 2 columns apart
      rects = args.layout.rect_group row:   11,
                                     col_offset: {
                                       count: args.state.sound_files.length,
                                       w:     2
                                     },
                                     dcol:  2,
                                     w:     2,
                                     h:     1,
                                     group: args.state.sound_files
  
      # now that you have the rects
      # construct the metadata for the buttons
      rects.map do |rect|
        {
          rect: rect,
          name: rect.name,
          path: rect.path,
          primitives: [
            rect.to_border(r: 255, g: 255, b: 255),
            rect.to_label(x: rect.center_x,
                          y: rect.center_y,
                          text: "#{rect.name}",
                          alignment_enum: 1,
                          vertical_alignment_enum: 1,
                          r: 255, g: 255, b: 255)
          ]
        }
      end
    end
  
    if args.inputs.mouse.up
      args.state.mouse_state = :released
      args.state.dragging_source = false
    elsif args.inputs.mouse.down
      args.state.mouse_state = :held
    end
  
    args.outputs.background_color = [ 0, 0, 0, 255 ]
  end
  
  def render args
    render_ui args
    render_sources args
  end

#+end_src

*** Advanced Audio - Audio Mixer - server_ip_address.txt
#+begin_src ruby
  # ./samples/07_advanced_audio/01_audio_mixer/app/server_ip_address.txt
  192.168.1.65
#+end_src

*** Advanced Audio - Sound Synthesis - main.rb
#+begin_src ruby
  # ./samples/07_advanced_audio/02_sound_synthesis/app/main.rb
  begin # region: top level tick methods
    def tick args
      defaults args
      render args
      input args
      process_audio_queue args
    end
  
    def defaults args
      args.state.sine_waves      ||= {}
      args.state.square_waves    ||= {}
      args.state.saw_tooth_waves ||= {}
      args.state.triangle_waves  ||= {}
      args.state.audio_queue     ||= []
      args.state.buttons         ||= [
        (frequency_buttons args),
        (sine_wave_note_buttons args),
        (bell_buttons args),
        (square_wave_note_buttons args),
        (saw_tooth_wave_note_buttons args),
        (triangle_wave_note_buttons args),
      ].flatten
    end
  
    def render args
      args.outputs.borders << args.state.buttons.map { |b| b[:border] }
      args.outputs.labels  << args.state.buttons.map { |b| b[:label]  }
      args.outputs.labels  << args.layout
                                .rect(row: 0, col: 11.5)
                                .yield_self { |r| r.merge y: r.y + r.h }
                                .merge(text: "This is a Pro only feature. Click here to watch the YouTube video if you are on the Standard License.",
                                       alignment_enum: 1)
    end
  
  
    def input args
      args.state.buttons.each do |b|
        if args.inputs.mouse.click && (args.inputs.mouse.click.inside_rect? b[:rect])
          parameter_string = (b.slice :frequency, :note, :octave).map { |k, v| "#{k}: #{v}" }.join ", "
          args.gtk.notify! "#{b[:method_to_call]} #{parameter_string}"
          send b[:method_to_call], args, b
        end
      end
  
      if args.inputs.mouse.click && (args.inputs.mouse.click.inside_rect? (args.layout.rect(row: 0).yield_self { |r| r.merge y: r.y + r.h.half, h: r.h.half }))
        args.gtk.openurl 'https://www.youtube.com/watch?v=zEzovM5jT-k&ab_channel=AmirRajan'
      end
    end
  
    def process_audio_queue args
      to_queue = args.state.audio_queue.find_all { |v| v[:queue_at] <= args.tick_count }
      args.state.audio_queue -= to_queue
      to_queue.each { |a| args.audio[a[:id]] = a }
  
      args.audio.find_all { |k, v| v[:decay_rate] }
        .each     { |k, v| v[:gain] -= v[:decay_rate] }
  
      sounds_to_stop = args.audio
                         .find_all { |k, v| v[:stop_at] && args.state.tick_count >= v[:stop_at] }
                         .map { |k, v| k }
  
      sounds_to_stop.each { |k| args.audio.delete k }
    end
  end
  
  begin # region: button definitions, ui layout, callback functions
    def button args, opts
      button_def = opts.merge rect: (args.layout.rect (opts.merge w: 2, h: 1))
  
      button_def[:border] = button_def[:rect].merge r: 0, g: 0, b: 0
  
      label_offset_x = 5
      label_offset_y = 30
  
      button_def[:label]  = button_def[:rect].merge text: opts[:text],
                                                    size_enum: -2.5,
                                                    x: button_def[:rect].x + label_offset_x,
                                                    y: button_def[:rect].y + label_offset_y
  
      button_def
    end
  
    def play_sine_wave args, sender
      queue_sine_wave args,
                      frequency: sender[:frequency],
                      duration: 1.seconds,
                      fade_out: true
    end
  
    def play_note args, sender
      method_to_call = :queue_sine_wave
      method_to_call = :queue_square_wave    if sender[:type] == :square
      method_to_call = :queue_saw_tooth_wave if sender[:type] == :saw_tooth
      method_to_call = :queue_triangle_wave  if sender[:type] == :triangle
      method_to_call = :queue_bell           if sender[:type] == :bell
  
      send method_to_call, args,
           frequency: (frequency_for note: sender[:note], octave: sender[:octave]),
           duration: 1.seconds,
           fade_out: true
    end
  
    def frequency_buttons args
      [
        (button args,
                row: 4.0, col: 0, text: "300hz",
                frequency: 300,
                method_to_call: :play_sine_wave),
        (button args,
                row: 5.0, col: 0, text: "400hz",
                frequency: 400,
                method_to_call: :play_sine_wave),
        (button args,
                row: 6.0, col: 0, text: "500hz",
                frequency: 500,
                method_to_call: :play_sine_wave),
      ]
    end
  
    def sine_wave_note_buttons args
      [
        (button args,
                row: 1.5, col: 2, text: "Sine C4",
                note: :c, octave: 4, type: :sine, method_to_call: :play_note),
        (button args,
                row: 2.5, col: 2, text: "Sine D4",
                note: :d, octave: 4, type: :sine, method_to_call: :play_note),
        (button args,
                row: 3.5, col: 2, text: "Sine E4",
                note: :e, octave: 4, type: :sine, method_to_call: :play_note),
        (button args,
                row: 4.5, col: 2, text: "Sine F4",
                note: :f, octave: 4, type: :sine, method_to_call: :play_note),
        (button args,
                row: 5.5, col: 2, text: "Sine G4",
                note: :g, octave: 4, type: :sine, method_to_call: :play_note),
        (button args,
                row: 6.5, col: 2, text: "Sine A5",
                note: :a, octave: 5, type: :sine, method_to_call: :play_note),
        (button args,
                row: 7.5, col: 2, text: "Sine B5",
                note: :b, octave: 5, type: :sine, method_to_call: :play_note),
        (button args,
                row: 8.5, col: 2, text: "Sine C5",
                note: :c, octave: 5, type: :sine, method_to_call: :play_note),
      ]
    end
  
    def square_wave_note_buttons args
      [
        (button args,
                row: 1.5, col: 6, text: "Square C4",
                note: :c, octave: 4, type: :square, method_to_call: :play_note),
        (button args,
                row: 2.5, col: 6, text: "Square D4",
                note: :d, octave: 4, type: :square, method_to_call: :play_note),
        (button args,
                row: 3.5, col: 6, text: "Square E4",
                note: :e, octave: 4, type: :square, method_to_call: :play_note),
        (button args,
                row: 4.5, col: 6, text: "Square F4",
                note: :f, octave: 4, type: :square, method_to_call: :play_note),
        (button args,
                row: 5.5, col: 6, text: "Square G4",
                note: :g, octave: 4, type: :square, method_to_call: :play_note),
        (button args,
                row: 6.5, col: 6, text: "Square A5",
                note: :a, octave: 5, type: :square, method_to_call: :play_note),
        (button args,
                row: 7.5, col: 6, text: "Square B5",
                note: :b, octave: 5, type: :square, method_to_call: :play_note),
        (button args,
                row: 8.5, col: 6, text: "Square C5",
                note: :c, octave: 5, type: :square, method_to_call: :play_note),
      ]
    end
    def saw_tooth_wave_note_buttons args
      [
        (button args,
                row: 1.5, col: 8, text: "Saw C4",
                note: :c, octave: 4, type: :saw_tooth, method_to_call: :play_note),
        (button args,
                row: 2.5, col: 8, text: "Saw D4",
                note: :d, octave: 4, type: :saw_tooth, method_to_call: :play_note),
        (button args,
                row: 3.5, col: 8, text: "Saw E4",
                note: :e, octave: 4, type: :saw_tooth, method_to_call: :play_note),
        (button args,
                row: 4.5, col: 8, text: "Saw F4",
                note: :f, octave: 4, type: :saw_tooth, method_to_call: :play_note),
        (button args,
                row: 5.5, col: 8, text: "Saw G4",
                note: :g, octave: 4, type: :saw_tooth, method_to_call: :play_note),
        (button args,
                row: 6.5, col: 8, text: "Saw A5",
                note: :a, octave: 5, type: :saw_tooth, method_to_call: :play_note),
        (button args,
                row: 7.5, col: 8, text: "Saw B5",
                note: :b, octave: 5, type: :saw_tooth, method_to_call: :play_note),
        (button args,
                row: 8.5, col: 8, text: "Saw C5",
                note: :c, octave: 5, type: :saw_tooth, method_to_call: :play_note),
      ]
    end
  
    def triangle_wave_note_buttons args
      [
        (button args,
                row: 1.5, col: 10, text: "Triangle C4",
                note: :c, octave: 4, type: :triangle, method_to_call: :play_note),
        (button args,
                row: 2.5, col: 10, text: "Triangle D4",
                note: :d, octave: 4, type: :triangle, method_to_call: :play_note),
        (button args,
                row: 3.5, col: 10, text: "Triangle E4",
                note: :e, octave: 4, type: :triangle, method_to_call: :play_note),
        (button args,
                row: 4.5, col: 10, text: "Triangle F4",
                note: :f, octave: 4, type: :triangle, method_to_call: :play_note),
        (button args,
                row: 5.5, col: 10, text: "Triangle G4",
                note: :g, octave: 4, type: :triangle, method_to_call: :play_note),
        (button args,
                row: 6.5, col: 10, text: "Triangle A5",
                note: :a, octave: 5, type: :triangle, method_to_call: :play_note),
        (button args,
                row: 7.5, col: 10, text: "Triangle B5",
                note: :b, octave: 5, type: :triangle, method_to_call: :play_note),
        (button args,
                row: 8.5, col: 10, text: "Triangle C5",
                note: :c, octave: 5, type: :triangle, method_to_call: :play_note),
      ]
    end
  
    def bell_buttons args
      [
        (button args,
                row: 1.5, col: 4, text: "Bell C4",
                note: :c, octave: 4, type: :bell, method_to_call: :play_note),
        (button args,
                row: 2.5, col: 4, text: "Bell D4",
                note: :d, octave: 4, type: :bell, method_to_call: :play_note),
        (button args,
                row: 3.5, col: 4, text: "Bell E4",
                note: :e, octave: 4, type: :bell, method_to_call: :play_note),
        (button args,
                row: 4.5, col: 4, text: "Bell F4",
                note: :f, octave: 4, type: :bell, method_to_call: :play_note),
        (button args,
                row: 5.5, col: 4, text: "Bell G4",
                note: :g, octave: 4, type: :bell, method_to_call: :play_note),
        (button args,
                row: 6.5, col: 4, text: "Bell A5",
                note: :a, octave: 5, type: :bell, method_to_call: :play_note),
        (button args,
                row: 7.5, col: 4, text: "Bell B5",
                note: :b, octave: 5, type: :bell, method_to_call: :play_note),
        (button args,
                row: 8.5, col: 4, text: "Bell C5",
                note: :c, octave: 5, type: :bell, method_to_call: :play_note),
      ]
    end
  end
  
  begin # region: wave generation
    begin # sine wave
      def defaults_sine_wave_for
        { frequency: 440, sample_rate: 48000 }
      end
  
      def sine_wave_for opts = {}
        opts = defaults_sine_wave_for.merge opts
        frequency   = opts[:frequency]
        sample_rate = opts[:sample_rate]
        period_size = (sample_rate.fdiv frequency).ceil
        period_size.map_with_index do |i|
          Math::sin((2.0 * Math::PI) / (sample_rate.to_f / frequency.to_f) * i)
        end.to_a
      end
  
      def defaults_queue_sine_wave
        { frequency: 440, duration: 60, gain: 1.0, fade_out: false, queue_in: 0 }
      end
  
      def queue_sine_wave args, opts = {}
        opts        = defaults_queue_sine_wave.merge opts
        frequency   = opts[:frequency]
        sample_rate = 48000
  
        sine_wave = sine_wave_for frequency: frequency, sample_rate: sample_rate
        args.state.sine_waves[frequency] ||= sine_wave_for frequency: frequency, sample_rate: sample_rate
  
        proc = lambda do
          generate_audio_data args.state.sine_waves[frequency], sample_rate
        end
  
        audio_state = new_audio_state args, opts
        audio_state[:input] = [1, sample_rate, proc]
        queue_audio args, audio_state: audio_state, wave: sine_wave
      end
    end
  
    begin # region: square wave
      def defaults_square_wave_for
        { frequency: 440, sample_rate: 48000 }
      end
  
      def square_wave_for opts = {}
        opts = defaults_square_wave_for.merge opts
        sine_wave = sine_wave_for opts
        sine_wave.map do |v|
          if v >= 0
            1.0
          else
            -1.0
          end
        end.to_a
      end
  
      def defaults_queue_square_wave
        { frequency: 440, duration: 60, gain: 0.3, fade_out: false, queue_in: 0 }
      end
  
      def queue_square_wave args, opts = {}
        opts        = defaults_queue_square_wave.merge opts
        frequency   = opts[:frequency]
        sample_rate = 48000
  
        square_wave = square_wave_for frequency: frequency, sample_rate: sample_rate
        args.state.square_waves[frequency] ||= square_wave_for frequency: frequency, sample_rate: sample_rate
  
        proc = lambda do
          generate_audio_data args.state.square_waves[frequency], sample_rate
        end
  
        audio_state = new_audio_state args, opts
        audio_state[:input] = [1, sample_rate, proc]
        queue_audio args, audio_state: audio_state, wave: square_wave
      end
    end
  
    begin # region: saw tooth wave
      def defaults_saw_tooth_wave_for
        { frequency: 440, sample_rate: 48000 }
      end
  
      def saw_tooth_wave_for opts = {}
        opts = defaults_saw_tooth_wave_for.merge opts
        sine_wave = sine_wave_for opts
        period_size = sine_wave.length
        sine_wave.map_with_index do |v, i|
          (((i % period_size).fdiv period_size) * 2) - 1
        end
      end
  
      def defaults_queue_saw_tooth_wave
        { frequency: 440, duration: 60, gain: 0.3, fade_out: false, queue_in: 0 }
      end
  
      def queue_saw_tooth_wave args, opts = {}
        opts        = defaults_queue_saw_tooth_wave.merge opts
        frequency   = opts[:frequency]
        sample_rate = 48000
  
        saw_tooth_wave = saw_tooth_wave_for frequency: frequency, sample_rate: sample_rate
        args.state.saw_tooth_waves[frequency] ||= saw_tooth_wave_for frequency: frequency, sample_rate: sample_rate
  
        proc = lambda do
          generate_audio_data args.state.saw_tooth_waves[frequency], sample_rate
        end
  
        audio_state = new_audio_state args, opts
        audio_state[:input] = [1, sample_rate, proc]
        queue_audio args, audio_state: audio_state, wave: saw_tooth_wave
      end
    end
  
    begin # region: triangle wave
      def defaults_triangle_wave_for
        { frequency: 440, sample_rate: 48000 }
      end
  
      def triangle_wave_for opts = {}
        opts = defaults_saw_tooth_wave_for.merge opts
        sine_wave = sine_wave_for opts
        period_size = sine_wave.length
        sine_wave.map_with_index do |v, i|
          ratio = (i.fdiv period_size)
          if ratio <= 0.5
            (ratio * 4) - 1
          else
            ratio -= 0.5
            1 - (ratio * 4)
          end
        end
      end
  
      def defaults_queue_triangle_wave
        { frequency: 440, duration: 60, gain: 1.0, fade_out: false, queue_in: 0 }
      end
  
      def queue_triangle_wave args, opts = {}
        opts        = defaults_queue_triangle_wave.merge opts
        frequency   = opts[:frequency]
        sample_rate = 48000
  
        triangle_wave = triangle_wave_for frequency: frequency, sample_rate: sample_rate
        args.state.triangle_waves[frequency] ||= triangle_wave_for frequency: frequency, sample_rate: sample_rate
  
        proc = lambda do
          generate_audio_data args.state.triangle_waves[frequency], sample_rate
        end
  
        audio_state = new_audio_state args, opts
        audio_state[:input] = [1, sample_rate, proc]
        queue_audio args, audio_state: audio_state, wave: triangle_wave
      end
    end
  
    begin # region: bell
      def defaults_queue_bell
        { frequency: 440, duration: 1.seconds, queue_in: 0 }
      end
  
      def queue_bell args, opts = {}
        (bell_to_sine_waves (defaults_queue_bell.merge opts)).each { |b| queue_sine_wave args, b }
      end
  
      def bell_harmonics
        [
          { frequency_ratio: 0.5, duration_ratio: 1.00 },
          { frequency_ratio: 1.0, duration_ratio: 0.80 },
          { frequency_ratio: 2.0, duration_ratio: 0.60 },
          { frequency_ratio: 3.0, duration_ratio: 0.40 },
          { frequency_ratio: 4.2, duration_ratio: 0.25 },
          { frequency_ratio: 5.4, duration_ratio: 0.20 },
          { frequency_ratio: 6.8, duration_ratio: 0.15 }
        ]
      end
  
      def defaults_bell_to_sine_waves
        { frequency: 440, duration: 1.seconds, queue_in: 0 }
      end
  
      def bell_to_sine_waves opts = {}
        opts = defaults_bell_to_sine_waves.merge opts
        bell_harmonics.map do |b|
          {
            frequency: opts[:frequency] * b[:frequency_ratio],
            duration:  opts[:duration] * b[:duration_ratio],
            queue_in:  opts[:queue_in],
            gain:      (1.fdiv bell_harmonics.length),
            fade_out:  true
          }
        end
      end
    end
  
    begin # audio entity construction
      def generate_audio_data sine_wave, sample_rate
        sample_size = (sample_rate.fdiv (1000.fdiv 60)).ceil
        copy_count  = (sample_size.fdiv sine_wave.length).ceil
        sine_wave * copy_count
      end
  
      def defaults_new_audio_state
        { frequency: 440, duration: 60, gain: 1.0, fade_out: false, queue_in: 0 }
      end
  
      def new_audio_state args, opts = {}
        opts        = defaults_new_audio_state.merge opts
        decay_rate  = 0
        decay_rate  = 1.fdiv(opts[:duration]) * opts[:gain] if opts[:fade_out]
        frequency   = opts[:frequency]
        sample_rate = 48000
  
        {
          id:               (new_id! args),
          frequency:        frequency,
          sample_rate:      48000,
          stop_at:          args.tick_count + opts[:queue_in] + opts[:duration],
          gain:             opts[:gain].to_f,
          queue_at:         args.state.tick_count + opts[:queue_in],
          decay_rate:       decay_rate,
          pitch:            1.0,
          looping:          true,
          paused:           false
        }
      end
  
      def queue_audio args, opts = {}
        graph_wave args, opts[:wave], opts[:audio_state][:frequency]
        args.state.audio_queue << opts[:audio_state]
      end
  
      def new_id! args
        args.state.audio_id ||= 0
        args.state.audio_id  += 1
      end
  
      def graph_wave args, wave, frequency
        if args.state.tick_count != args.state.graphed_at
          args.outputs.static_lines.clear
          args.outputs.static_sprites.clear
        end
  
        wave = wave
  
        r, g, b = frequency.to_i % 85,
                  frequency.to_i % 170,
                  frequency.to_i % 255
  
        starting_rect = args.layout.rect(row: 5, col: 13)
        x_scale    = 10
        y_scale    = 100
        max_points = 25
  
        points = wave
        if wave.length > max_points
          resolution = wave.length.idiv max_points
          points = wave.find_all.with_index { |y, i| (i % resolution == 0) }
        end
  
        args.outputs.static_lines << points.map_with_index do |y, x|
          next_y = points[x + 1]
  
          if next_y
            {
              x:  starting_rect.x + (x * x_scale),
              y:  starting_rect.y + starting_rect.h.half + y_scale * y,
              x2: starting_rect.x + ((x + 1) * x_scale),
              y2: starting_rect.y + starting_rect.h.half + y_scale * next_y,
              r:  r,
              g:  g,
              b:  b
            }
          end
        end
  
        args.outputs.static_sprites << points.map_with_index do |y, x|
          {
            x:  (starting_rect.x + (x * x_scale)) - 2,
            y:  (starting_rect.y + starting_rect.h.half + y_scale * y) - 2,
            w:  4,
            h:  4,
            path: 'sprites/square-white.png',
            r: r,
            g: g,
            b: b
          }
        end
  
        args.state.graphed_at = args.state.tick_count
      end
    end
  
    begin # region: musical note mapping
      def defaults_frequency_for
        { note: :a, octave: 5, sharp:  false, flat:   false }
      end
  
      def frequency_for opts = {}
        opts = defaults_frequency_for.merge opts
        octave_offset_multiplier  = opts[:octave] - 5
        note = note_frequencies_octave_5[opts[:note]]
        if octave_offset_multiplier < 0
          note = note * 1 / (octave_offset_multiplier.abs + 1)
        elsif octave_offset_multiplier > 0
          note = note * (octave_offset_multiplier.abs + 1) / 1
        end
        note
      end
  
      def note_frequencies_octave_5
        {
          a: 440.0,
          a_sharp: 466.16, b_flat: 466.16,
          b: 493.88,
          c: 523.25,
          c_sharp: 554.37, d_flat: 587.33,
          d: 587.33,
          d_sharp: 622.25, e_flat: 659.25,
          e: 659.25,
          f: 698.25,
          f_sharp: 739.99, g_flat: 739.99,
          g: 783.99,
          g_sharp: 830.61, a_flat: 830.61
        }
      end
    end
  end
  
  $gtk.reset

#+end_src

*** Advanced Rendering - Labels With Wrapped Text - main.rb
#+begin_src ruby
  # ./samples/07_advanced_rendering/00_labels_with_wrapped_text/app/main.rb
  def tick args
    # defaults
    args.state.scroll_location  ||= 0
    args.state.textbox.messages ||= []
    args.state.textbox.scroll   ||= 0
  
    # render
    args.outputs.background_color = [0, 0, 0, 255]
    render_messages args
    render_instructions args
  
    # inputs
    if args.inputs.keyboard.key_down.one
      queue_message args, "Hello there neighbour! my name is mark, how is your day today?"
    end
  
    if args.inputs.keyboard.key_down.two
      queue_message args, "I'm doing great sir, actually I'm having a picnic today"
    end
  
    if args.inputs.keyboard.key_down.three
      queue_message args, "Well that sounds wonderful!"
    end
  
    if args.inputs.keyboard.key_down.home
      args.state.scroll_location = 1
    end
  
    if args.inputs.keyboard.key_down.delete
      clear_message_queue args
    end
  end
  
  def queue_message args, msg
    args.state.textbox.messages.concat msg.wrapped_lines 50
  end
  
  def clear_message_queue args
    args.state.textbox.messages = nil
    args.state.textbox.scroll = 0
  end
  
  def render_messages args
    args.outputs[:textbox].w = 400
    args.outputs[:textbox].h = 720
  
    args.outputs.primitives << args.state.textbox.messages.each_with_index.map do |s, idx|
      {
        x: 0,
        y: 20 * (args.state.textbox.messages.size - idx) + args.state.textbox.scroll * 20,
        text: s,
        size_enum: -3,
        alignment_enum: 0,
        r: 255, g:255, b: 255, a: 255
      }
    end
  
    args.outputs[:textbox].labels << args.state.textbox.messages.each_with_index.map do |s, idx|
      {
        x: 0,
        y: 20 * (args.state.textbox.messages.size - idx) + args.state.textbox.scroll * 20,
        text: s,
        size_enum: -3,
        alignment_enum: 0,
        r: 255, g:255, b: 255, a: 255
      }
    end
  
    args.outputs[:textbox].borders << [0, 0, args.outputs[:textbox].w, 720]
  
    args.state.textbox.scroll += args.inputs.mouse.wheel.y unless args.inputs.mouse.wheel.nil?
  
    if args.state.scroll_location > 0
      args.state.textbox.scroll = 0
      args.state.scroll_location = 0
    end
  
    args.outputs.sprites << [900, 0, args.outputs[:textbox].w, 720, :textbox]
  end
  
  def render_instructions args
    args.outputs.labels << [30,
                            30.from_top,
                            "press 1, 2, 3 to display messages, MOUSE WHEEL to scroll, HOME to go to top, BACKSPACE to delete.",
                            0, 255, 255]
  
    args.outputs.primitives << [0, 55.from_top, 1280, 30, :pixel, 0, 255, 0, 0, 0].sprite
  end

#+end_src

*** Advanced Rendering - Rotating Label - main.rb
#+begin_src ruby
  # ./samples/07_advanced_rendering/00_rotating_label/app/main.rb
  def tick args
    # set the render target width and height to match the label
    args.outputs[:scene].w = 220
    args.outputs[:scene].h = 30
  
  
    # make the background transparent
    args.outputs[:scene].background_color = [255, 255, 255, 0]
  
    # set the blendmode of the label to 0 (no blending)
    # center it inside of the scene
    # set the vertical_alignment_enum to 1 (center)
    args.outputs[:scene].labels  << { x: 0,
                                      y: 15,
                                      text: "label in render target",
                                      blendmode_enum: 0,
                                      vertical_alignment_enum: 1 }
  
    # add a border to the render target
    args.outputs[:scene].borders << { x: 0,
                                      y: 0,
                                      w: args.outputs[:scene].w,
                                      h: args.outputs[:scene].h }
  
    # add the rendertarget to the main output as a sprite
    args.outputs.sprites << { x: 640 - args.outputs[:scene].w.half,
                              y: 360 - args.outputs[:scene].h.half,
                              w: args.outputs[:scene].w,
                              h: args.outputs[:scene].h,
                              angle: args.state.tick_count,
                              path: :scene }
  end

#+end_src

*** Advanced Rendering - Simple Render Targets - main.rb
#+begin_src ruby
  # ./samples/07_advanced_rendering/01_simple_render_targets/app/main.rb
  def tick args
    # args.outputs.render_targets are really really powerful.
    # They essentially allow you to create a sprite programmatically and cache the result.
  
    # Create a render_target of a :block and a :gradient on tick zero.
    if args.state.tick_count == 0
      args.render_target(:block).solids << [0, 0, 1280, 100]
  
      # The gradient is actually just a collection of black solids with increasing
      # opacities.
      args.render_target(:gradient).solids << 90.map_with_index do |x|
        50.map_with_index do |y|
          [x * 15, y * 15, 15, 15, 0, 0, 0, (x * 3).fdiv(255) * 255]
        end
      end
    end
  
    # Take the :block render_target and present it horizontally centered.
    # Use a subsection of the render_targetd specified by source_x,
    # source_y, source_w, source_h.
    args.outputs.sprites << { x: 0,
                              y: 310,
                              w: 1280,
                              h: 100,
                              path: :block,
                              source_x: 0,
                              source_y: 0,
                              source_w: 1280,
                              source_h: 100 }
  
    # After rendering :block, render gradient on top of :block.
    args.outputs.sprites << [0, 0, 1280, 720, :gradient]
  
    args.outputs.labels  << [1270, 710, args.gtk.current_framerate, 0, 2, 255, 255, 255]
    tick_instructions args, "Sample app shows how to use render_targets (programmatically create cached sprites)."
  end
  
  def tick_instructions args, text, y = 715
    return if args.state.key_event_occurred
    if args.inputs.mouse.click ||
       args.inputs.keyboard.directional_vector ||
       args.inputs.keyboard.key_down.enter ||
       args.inputs.keyboard.key_down.escape
      args.state.key_event_occurred = true
    end
  
    args.outputs.debug << [0, y - 50, 1280, 60].solid
    args.outputs.debug << [640, y, text, 1, 1, 255, 255, 255].label
    args.outputs.debug << [640, y - 25, "(click to dismiss instructions)" , -2, 1, 255, 255, 255].label
  end
  
  $gtk.reset

#+end_src

*** Advanced Rendering - Render Targets With Tile Manipulation - main.rb
#+begin_src ruby
  # ./samples/07_advanced_rendering/02_render_targets_with_tile_manipulation/app/main.rb
  # This sample is meant to show you how to do that dripping transition thing
  #  at the start of the original Doom. Most of this file is here to animate
  #  a scene to wipe away; the actual wipe effect is in the last 20 lines or
  #  so.
  
  $gtk.reset   # reset all game state if reloaded.
  
  def circle_of_blocks pass, xoffset, yoffset, angleoffset, blocksize, distance
    numblocks = 10
  
    for i in 1..numblocks do
      angle = ((360 / numblocks) * i) + angleoffset
      radians = angle * (Math::PI / 180)
      x = (xoffset + (distance * Math.cos(radians))).round
      y = (yoffset + (distance * Math.sin(radians))).round
      pass.solids << [ x, y, blocksize, blocksize, 255, 255, 0 ]
    end
  end
  
  def draw_scene args, pass
    pass.solids << [0, 360, 1280, 360, 0, 0, 200]
    pass.solids << [0, 0, 1280, 360, 0, 127, 0]
  
    blocksize = 100
    angleoffset = args.state.tick_count * 2.5
    centerx = (1280 - blocksize) / 2
    centery = (720 - blocksize) / 2
  
    circle_of_blocks pass, centerx, centery, angleoffset, blocksize * 2, 500
    circle_of_blocks pass, centerx, centery, angleoffset, blocksize, 325
    circle_of_blocks pass, centerx, centery, angleoffset, blocksize / 2, 200
    circle_of_blocks pass, centerx, centery, angleoffset, blocksize / 4, 100
  end
  
  def tick args
    segments = 160
  
    # On the first tick, initialize some stuff.
    if !args.state.yoffsets
      args.state.baseyoff = 0
      args.state.yoffsets = []
      for i in 0..segments do
        args.state.yoffsets << rand * 100
      end
    end
  
    # Just draw some random stuff for a few seconds.
    args.state.static_debounce ||= 60 * 2.5
    if args.state.static_debounce > 0
      last_frame = args.state.static_debounce == 1
      target = last_frame ? args.render_target(:last_frame) : args.outputs
      draw_scene args, target
      args.state.static_debounce -= 1
      return unless last_frame
    end
  
    # build up the wipe...
  
    # this is the thing we're wiping to.
    args.outputs.sprites << [ 0, 0, 1280, 720, 'dragonruby.png' ]
  
    return if (args.state.baseyoff > (1280 + 100))  # stop when done sliding
  
    segmentw = 1280 / segments
  
    x = 0
    for i in 0..segments do
      yoffset = 0
      if args.state.yoffsets[i] < args.state.baseyoff
        yoffset = args.state.baseyoff - args.state.yoffsets[i]
      end
  
      # (720 - yoffset) flips the coordinate system, (- 720) adjusts for the height of the segment.
      args.outputs.sprites << [ x, (720 - yoffset) - 720, segmentw, 720, 'last_frame', 0, 255, 255, 255, 255, x, 0, segmentw, 720 ]
      x += segmentw
    end
  
    args.state.baseyoff += 4
  
    tick_instructions args, "Sample app shows an advanced usage of render_target."
  end
  
  def tick_instructions args, text, y = 715
    return if args.state.key_event_occurred
    if args.inputs.mouse.click ||
       args.inputs.keyboard.directional_vector ||
       args.inputs.keyboard.key_down.enter ||
       args.inputs.keyboard.key_down.escape
      args.state.key_event_occurred = true
    end
  
    args.outputs.debug << [0, y - 50, 1280, 60].solid
    args.outputs.debug << [640, y, text, 1, 1, 255, 255, 255].label
    args.outputs.debug << [640, y - 25, "(click to dismiss instructions)" , -2, 1, 255, 255, 255].label
  end

#+end_src

*** Advanced Rendering - Render Target Viewports - main.rb
#+begin_src ruby
  # ./samples/07_advanced_rendering/03_render_target_viewports/app/main.rb
  =begin
  
   APIs listing that haven't been encountered in previous sample apps:
  
   - args.state.new_entity: Used when we want to create a new object, like a sprite or button.
     For example, if we want to create a new button, we would declare it as a new entity and
     then define its properties. (Remember, you can use state to define ANY property and it will
     be retained across frames.)
  
     If you have a solar system and you're creating args.state.sun and setting its image path to an
     image in the sprites folder, you would do the following:
     (See samples/99_sample_nddnug_workshop for more details.)
  
     args.state.sun ||= args.state.new_entity(:sun) do |s|
     s.path = 'sprites/sun.png'
     end
  
   - String interpolation: Uses #{} syntax; everything between the #{ and the } is evaluated
     as Ruby code, and the placeholder is replaced with its corresponding value or result.
  
     For example, if we have a variable
     name = "Ruby"
     then the line
     puts "How are you, #{name}?"
     would print "How are you, Ruby?" to the console.
     (Remember, string interpolation only works with double quotes!)
  
   - Ternary operator (?): Similar to if statement; first evalulates whether a statement is
     true or false, and then executes a command depending on that result.
     For example, if we had a variable
     grade = 75
     and used the ternary operator in the command
     pass_or_fail = grade > 65 ? "pass" : "fail"
     then the value of pass_or_fail would be "pass" since grade's value was greater than 65.
  
   Reminders:
  
   - args.grid.(left|right|top|bottom): Pixel value for the boundaries of the virtual
     720 p screen (Dragon Ruby Game Toolkits's virtual resolution is always 1280x720).
  
   - Numeric#shift_(left|right|up|down): Shifts the Numeric in the correct direction
     by adding or subracting.
  
   - ARRAY#inside_rect?: An array with at least two values is considered a point. An array
     with at least four values is considered a rect. The inside_rect? function returns true
     or false depending on if the point is inside the rect.
  
   - ARRAY#intersect_rect?: Returns true or false depending on if the two rectangles intersect.
  
   - args.inputs.mouse.click: This property will be set if the mouse was clicked.
     For more information about the mouse, go to mygame/documentation/07-mouse.md.
  
   - args.inputs.keyboard.key_up.KEY: The value of the properties will be set
     to the frame  that the key_up event occurred (the frame correlates
     to args.state.tick_count).
     For more information about the keyboard, go to mygame/documentation/06-keyboard.md.
  
   - args.state.labels:
     The parameters for a label are
     1. the position (x, y)
     2. the text
     3. the size
     4. the alignment
     5. the color (red, green, and blue saturations)
     6. the alpha (or transparency)
     For more information about labels, go to mygame/documentation/02-labels.md.
  
   - args.state.lines:
     The parameters for a line are
     1. the starting position (x, y)
     2. the ending position (x2, y2)
     3. the color (red, green, and blue saturations)
     4. the alpha (or transparency)
     For more information about lines, go to mygame/documentation/04-lines.md.
  
   - args.state.solids (and args.state.borders):
     The parameters for a solid (or border) are
     1. the position (x, y)
     2. the width (w)
     3. the height (h)
     4. the color (r, g, b)
     5. the alpha (or transparency)
     For more information about solids and borders, go to mygame/documentation/03-solids-and-borders.md.
  
   - args.state.sprites:
     The parameters for a sprite are
     1. the position (x, y)
     2. the width (w)
     3. the height (h)
     4. the image path
     5. the angle
     6. the alpha (or transparency)
     For more information about sprites, go to mygame/documentation/05-sprites.md.
  =end
  
  # This sample app shows different objects that can be used when making games, such as labels,
  # lines, sprites, solids, buttons, etc. Each demo section shows how these objects can be used.
  
  # Also note that state.tick_count refers to the passage of time, or current frame.
  
  class TechDemo
    attr_accessor :inputs, :state, :outputs, :grid, :args
  
    # Calls all methods necessary for the app to run properly.
    def tick
      labels_tech_demo
      lines_tech_demo
      solids_tech_demo
      borders_tech_demo
      sprites_tech_demo
      keyboards_tech_demo
      controller_tech_demo
      mouse_tech_demo
      point_to_rect_tech_demo
      rect_to_rect_tech_demo
      button_tech_demo
      export_game_state_demo
      window_state_demo
      render_seperators
    end
  
    # Shows output of different kinds of labels on the screen
    def labels_tech_demo
      outputs.labels << [grid.left.shift_right(5), grid.top.shift_down(5), "This is a label located at the top left."]
      outputs.labels << [grid.left.shift_right(5), grid.bottom.shift_up(30), "This is a label located at the bottom left."]
      outputs.labels << [ 5, 690, "Labels (x, y, text, size, align, r, g, b, a)"]
      outputs.labels << [ 5, 660, "Smaller label.",  -2]
      outputs.labels << [ 5, 630, "Small label.",    -1]
      outputs.labels << [ 5, 600, "Medium label.",    0]
      outputs.labels << [ 5, 570, "Large label.",     1]
      outputs.labels << [ 5, 540, "Larger label.",    2]
      outputs.labels << [300, 660, "Left aligned.",    0, 2]
      outputs.labels << [300, 640, "Center aligned.",  0, 1]
      outputs.labels << [300, 620, "Right aligned.",   0, 0]
      outputs.labels << [175, 595, "Red Label.",       0, 0, 255,   0,   0]
      outputs.labels << [175, 575, "Green Label.",     0, 0,   0, 255,   0]
      outputs.labels << [175, 555, "Blue Label.",      0, 0,   0,   0, 255]
      outputs.labels << [175, 535, "Faded Label.",     0, 0,   0,   0,   0, 128]
    end
  
    # Shows output of lines on the screen
    def lines_tech_demo
      outputs.labels << [5, 500, "Lines (x, y, x2, y2, r, g, b, a)"]
      outputs.lines  << [5, 450, 100, 450]
      outputs.lines  << [5, 430, 300, 430]
      outputs.lines  << [5, 410, 300, 410, state.tick_count % 255, 0, 0, 255] # red saturation changes
      outputs.lines  << [5, 390 - state.tick_count % 25, 300, 390, 0, 0, 0, 255] # y position changes
      outputs.lines  << [5 + state.tick_count % 200, 360, 300, 360, 0, 0, 0, 255] # x position changes
    end
  
    # Shows output of different kinds of solids on the screen
    def solids_tech_demo
      outputs.labels << [  5, 350, "Solids (x, y, w, h, r, g, b, a)"]
      outputs.solids << [ 10, 270, 50, 50]
      outputs.solids << [ 70, 270, 50, 50, 0, 0, 0]
      outputs.solids << [130, 270, 50, 50, 255, 0, 0]
      outputs.solids << [190, 270, 50, 50, 255, 0, 0, 128]
      outputs.solids << [250, 270, 50, 50, 0, 0, 0, 128 + state.tick_count % 128] # transparency changes
    end
  
    # Shows output of different kinds of borders on the screen
    # The parameters for a border are the same as the parameters for a solid
    def borders_tech_demo
      outputs.labels <<  [  5, 260, "Borders (x, y, w, h, r, g, b, a)"]
      outputs.borders << [ 10, 180, 50, 50]
      outputs.borders << [ 70, 180, 50, 50, 0, 0, 0]
      outputs.borders << [130, 180, 50, 50, 255, 0, 0]
      outputs.borders << [190, 180, 50, 50, 255, 0, 0, 128]
      outputs.borders << [250, 180, 50, 50, 0, 0, 0, 128 + state.tick_count % 128] # transparency changes
    end
  
    # Shows output of different kinds of sprites on the screen
    def sprites_tech_demo
      outputs.labels <<  [   5, 170, "Sprites (x, y, w, h, path, angle, a)"]
      outputs.sprites << [  10, 40, 128, 101, 'dragonruby.png']
      outputs.sprites << [ 150, 40, 128, 101, 'dragonruby.png', state.tick_count % 360] # angle changes
      outputs.sprites << [ 300, 40, 128, 101, 'dragonruby.png', 0, state.tick_count % 255] # transparency changes
    end
  
    # Holds size, alignment, color (black), and alpha (transparency) parameters
    # Using small_font as a parameter accounts for all remaining parameters
    # so they don't have to be repeatedly typed
    def small_font
      [-2, 0, 0, 0, 0, 255]
    end
  
    # Sets position of each row
    # Converts given row value to pixels that DragonRuby understands
    def row_to_px row_number
  
      # Row 0 starts 5 units below the top of the grid.
      # Each row afterward is 20 units lower.
      grid.top.shift_down(5).shift_down(20 * row_number)
    end
  
    # Uses labels to output current game time (passage of time), and whether or not "h" was pressed
    # If "h" is pressed, the frame is output when the key_up event occurred
    def keyboards_tech_demo
      outputs.labels << [460, row_to_px(0), "Current game time: #{state.tick_count}", small_font]
      outputs.labels << [460, row_to_px(2), "Keyboard input: inputs.keyboard.key_up.h", small_font]
      outputs.labels << [460, row_to_px(3), "Press \"h\" on the keyboard.", small_font]
  
      if inputs.keyboard.key_up.h # if "h" key_up event occurs
        state.h_pressed_at = state.tick_count # frame it occurred is stored
      end
  
      # h_pressed_at is initially set to false, and changes once the user presses the "h" key.
      state.h_pressed_at ||= false
  
      if state.h_pressed_at # if h is pressed (pressed_at has a frame number and is no longer false)
        outputs.labels << [460, row_to_px(4), "\"h\" was pressed at time: #{state.h_pressed_at}", small_font]
      else # otherwise, label says "h" was never pressed
        outputs.labels << [460, row_to_px(4), "\"h\" has never been pressed.", small_font]
      end
  
      # border around keyboard input demo section
      outputs.borders << [455, row_to_px(5), 360, row_to_px(2).shift_up(5) - row_to_px(5)]
    end
  
    # Sets definition for a small label
    # Makes it easier to position labels in respect to the position of other labels
    def small_label x, row, message
      [x, row_to_px(row), message, small_font]
    end
  
    # Uses small labels to show whether the "a" button on the controller is down, held, or up.
    # y value of each small label is set by calling the row_to_px method
    def controller_tech_demo
      x = 460
      outputs.labels << small_label(x, 6, "Controller one input: inputs.controller_one")
      outputs.labels << small_label(x, 7, "Current state of the \"a\" button.")
      outputs.labels << small_label(x, 8, "Check console window for more info.")
  
      if inputs.controller_one.key_down.a # if "a" is in "down" state
        outputs.labels << small_label(x, 9, "\"a\" button down: #{inputs.controller_one.key_down.a}")
        puts "\"a\" button down at #{inputs.controller_one.key_down.a}" # prints frame the event occurred
      elsif inputs.controller_one.key_held.a # if "a" is held down
        outputs.labels << small_label(x, 9, "\"a\" button held: #{inputs.controller_one.key_held.a}")
      elsif inputs.controller_one.key_up.a # if "a" is in up state
        outputs.labels << small_label(x, 9, "\"a\" button up: #{inputs.controller_one.key_up.a}")
        puts "\"a\" key up at #{inputs.controller_one.key_up.a}"
      else # if no event has occurred
        outputs.labels << small_label(x, 9, "\"a\" button state is nil.")
      end
  
      # border around controller input demo section
      outputs.borders << [455, row_to_px(10), 360, row_to_px(6).shift_up(5) - row_to_px(10)]
    end
  
    # Outputs when the mouse was clicked, as well as the coordinates on the screen
    # of where the click occurred
    def mouse_tech_demo
      x = 460
  
      outputs.labels << small_label(x, 11, "Mouse input: inputs.mouse")
  
      if inputs.mouse.click # if click has a value and is not nil
        state.last_mouse_click = inputs.mouse.click # coordinates of click are stored
      end
  
      if state.last_mouse_click # if mouse is clicked (has coordinates as value)
        # outputs the time (frame) the click occurred, as well as how many frames have passed since the event
        outputs.labels << small_label(x, 12, "Mouse click happened at: #{state.last_mouse_click.created_at}, #{state.last_mouse_click.created_at_elapsed}")
        # outputs coordinates of click
        outputs.labels << small_label(x, 13, "Mouse click location: #{state.last_mouse_click.point.x}, #{state.last_mouse_click.point.y}")
      else # otherwise if the mouse has not been clicked
        outputs.labels << small_label(x, 12, "Mouse click has not occurred yet.")
        outputs.labels << small_label(x, 13, "Please click mouse.")
      end
    end
  
    # Outputs whether a mouse click occurred inside or outside of a box
    def point_to_rect_tech_demo
      x = 460
  
      outputs.labels << small_label(x, 15, "Click inside the blue box maybe ---->")
  
      box = [765, 370, 50, 50, 0, 0, 170] # blue box
      outputs.borders << box
  
      if state.last_mouse_click # if the mouse was clicked
        if state.last_mouse_click.point.inside_rect? box # if mouse clicked inside box
          outputs.labels << small_label(x, 16, "Mouse click happened inside the box.")
        else # otherwise, if mouse was clicked outside the box
          outputs.labels << small_label(x, 16, "Mouse click happened outside the box.")
        end
      else # otherwise, if was not clicked at all
        outputs.labels << small_label(x, 16, "Mouse click has not occurred yet.") # output if the mouse was not clicked
      end
  
      # border around mouse input demo section
      outputs.borders << [455, row_to_px(14), 360, row_to_px(11).shift_up(5) - row_to_px(14)]
    end
  
    # Outputs a red box onto the screen. A mouse click from the user inside of the red box will output
    # a smaller box. If two small boxes are inside of the red box, it will be determined whether or not
    # they intersect.
    def rect_to_rect_tech_demo
      x = 460
  
      outputs.labels << small_label(x, 17.5, "Click inside the red box below.") # label with instructions
      red_box = [460, 250, 355, 90, 170, 0, 0] # definition of the red box
      outputs.borders << red_box # output as a border (not filled in)
  
      # If the mouse is clicked inside the red box, two collision boxes are created.
      if inputs.mouse.click
        if inputs.mouse.click.point.inside_rect? red_box
          if !state.box_collision_one # if the collision_one box does not yet have a definition
            # Subtracts 25 from the x and y positions of the click point in order to make the click point the center of the box.
            # You can try deleting the subtraction to see how it impacts the box placement.
            state.box_collision_one = [inputs.mouse.click.point.x - 25, inputs.mouse.click.point.y - 25, 50, 50, 180, 0,   0, 180]  # sets definition
          elsif !state.box_collision_two # if collision_two does not yet have a definition
            state.box_collision_two = [inputs.mouse.click.point.x - 25, inputs.mouse.click.point.y - 25, 50, 50,   0, 0, 180, 180] # sets definition
          else
            state.box_collision_one = nil # both boxes are empty
            state.box_collision_two = nil
          end
        end
      end
  
      # If collision boxes exist, they are output onto screen inside the red box as solids
      if state.box_collision_one
        outputs.solids << state.box_collision_one
      end
  
      if state.box_collision_two
        outputs.solids << state.box_collision_two
      end
  
      # Outputs whether or not the two collision boxes intersect.
      if state.box_collision_one && state.box_collision_two # if both collision_boxes are defined (and not nil or empty)
        if state.box_collision_one.intersect_rect? state.box_collision_two # if the two boxes intersect
          outputs.labels << small_label(x, 23.5, 'The boxes intersect.')
        else # otherwise, if the two boxes do not intersect
          outputs.labels << small_label(x, 23.5, 'The boxes do not intersect.')
        end
      else
        outputs.labels << small_label(x, 23.5, '--') # if the two boxes are not defined (are nil or empty), this label is output
      end
    end
  
    # Creates a button and outputs it onto the screen using labels and borders.
    # If the button is clicked, the color changes to make it look faded.
    def button_tech_demo
      x, y, w, h = 460, 160, 300, 50
      state.button        ||= state.new_entity(:button_with_fade)
  
      # Adds w.half to x and h.half + 10 to y in order to display the text inside the button's borders.
      state.button.label  ||= [x + w.half, y + h.half + 10, "click me and watch me fade", 0, 1]
      state.button.border ||= [x, y, w, h]
  
      if inputs.mouse.click && inputs.mouse.click.point.inside_rect?(state.button.border) # if mouse is clicked, and clicked inside button's border
        state.button.clicked_at = inputs.mouse.click.created_at # stores the time the click occurred
      end
  
      outputs.labels << state.button.label
      outputs.borders << state.button.border
  
      if state.button.clicked_at # if button was clicked (variable has a value and is not nil)
  
        # The appearance of the button changes for 0.25 seconds after the time the button is clicked at.
        # The color changes (rgb is set to 0, 180, 80) and the transparency gradually changes.
        # Change 0.25 to 1.25 and notice that the transparency takes longer to return to normal.
        outputs.solids << [x, y, w, h, 0, 180, 80, 255 * state.button.clicked_at.ease(0.25.seconds, :flip)]
      end
    end
  
    # Creates a new button by declaring it as a new entity, and sets values.
    def new_button_prefab x, y, message
      w, h = 300, 50
      button        = state.new_entity(:button_with_fade)
      button.label  = [x + w.half, y + h.half + 10, message, 0, 1] # '+ 10' keeps label's text within button's borders
      button.border = [x, y, w, h] # sets border definition
      button
    end
  
    # If the mouse has been clicked and the click's location is inside of the button's border, that means
    # that the button has been clicked. This method returns a boolean value.
    def button_clicked? button
      inputs.mouse.click && inputs.mouse.click.point.inside_rect?(button.border)
    end
  
    # Determines if button was clicked, and changes its appearance if it is clicked
    def tick_button_prefab button
      outputs.labels << button.label # outputs button's label and border
      outputs.borders << button.border
  
      if button_clicked? button # if button is clicked
        button.clicked_at = inputs.mouse.click.created_at # stores the time that the button was clicked
      end
  
      if button.clicked_at # if clicked_at has a frame value and is not nil
        # button is output; color changes and transparency changes for 0.25 seconds after click occurs
        outputs.solids << [button.border.x, button.border.y, button.border.w, button.border.h,
                           0, 180, 80, 255 * button.clicked_at.ease(0.25.seconds, :flip)] # transparency changes for 0.25 seconds
      end
    end
  
    # Exports the app's game state if the export button is clicked.
    def export_game_state_demo
      state.export_game_state_button ||= new_button_prefab(460, 100, "click to export app state")
      tick_button_prefab(state.export_game_state_button) # calls method to output button
      if button_clicked? state.export_game_state_button # if the export button is clicked
        args.gtk.export! "Exported from clicking the export button in the tech demo." # the export occurs
      end
    end
  
    # The mouse and keyboard focus are set to "yes" when the Dragonruby window is the active window.
    def window_state_demo
      m = $gtk.args.inputs.mouse.has_focus ? 'Y' : 'N' # ternary operator (similar to if statement)
      k = $gtk.args.inputs.keyboard.has_focus ? 'Y' : 'N'
      outputs.labels << [460, 20, "mouse focus: #{m}   keyboard focus: #{k}", small_font]
    end
  
    #Sets values for the horizontal separator (divides demo sections)
    def horizontal_seperator y, x, x2
      [x, y, x2, y, 150, 150, 150]
    end
  
    #Sets the values for the vertical separator (divides demo sections)
    def vertical_seperator x, y, y2
      [x, y, x, y2, 150, 150, 150]
    end
  
    # Outputs vertical and horizontal separators onto the screen to separate each demo section.
    def render_seperators
      outputs.lines << horizontal_seperator(505, grid.left, 445)
      outputs.lines << horizontal_seperator(353, grid.left, 445)
      outputs.lines << horizontal_seperator(264, grid.left, 445)
      outputs.lines << horizontal_seperator(174, grid.left, 445)
  
      outputs.lines << vertical_seperator(445, grid.top, grid.bottom)
  
      outputs.lines << horizontal_seperator(690, 445, 820)
      outputs.lines << horizontal_seperator(426, 445, 820)
  
      outputs.lines << vertical_seperator(820, grid.top, grid.bottom)
    end
  end
  
  $tech_demo = TechDemo.new
  
  def tick args
    $tech_demo.inputs = args.inputs
    $tech_demo.state = args.state
    $tech_demo.grid = args.grid
    $tech_demo.args = args
    $tech_demo.outputs = args.render_target(:mini_map)
    $tech_demo.tick
    args.outputs.labels  << [830, 715, "Render target:", [-2, 0, 0, 0, 0, 255]]
    args.outputs.sprites << [0, 0, 1280, 720, :mini_map]
    args.outputs.sprites << [830, 300, 675, 379, :mini_map]
    tick_instructions args, "Sample app shows all the rendering apis available."
  end
  
  def tick_instructions args, text, y = 715
    return if args.state.key_event_occurred
    if args.inputs.mouse.click ||
       args.inputs.keyboard.directional_vector ||
       args.inputs.keyboard.key_down.enter ||
       args.inputs.keyboard.key_down.escape
      args.state.key_event_occurred = true
    end
  
    args.outputs.debug << [0, y - 50, 1280, 60].solid
    args.outputs.debug << [640, y, text, 1, 1, 255, 255, 255].label
    args.outputs.debug << [640, y - 25, "(click to dismiss instructions)" , -2, 1, 255, 255, 255].label
  end

#+end_src

*** Advanced Rendering - Render Primitive Hierarchies - main.rb
#+begin_src ruby
  # ./samples/07_advanced_rendering/04_render_primitive_hierarchies/app/main.rb
  =begin
  
   APIs listing that haven't been encountered in previous sample apps:
  
   - Nested array: An array whose individual elements are also arrays; useful for
     storing groups of similar data.  Also called multidimensional arrays.
  
     In this sample app, we see nested arrays being used in object definitions.
     Notice the parameters for solids, listed below. Parameters 1-3 set the
     definition for the rect, and parameter 4 sets the definition of the color.
  
     Instead of having a solid definition that looks like this,
     [X, Y, W, H, R, G, B]
     we can separate it into two separate array definitions in one, like this
     [[X, Y, W, H], [R, G, B]]
     and both options work fine in defining our solid (or any object).
  
   - Collections: Lists of data; useful for organizing large amounts of data.
     One element of a collection could be an array (which itself contains many elements).
     For example, a collection that stores two solid objects would look like this:
     [
      [100, 100, 50, 50, 0, 0, 0],
      [100, 150, 50, 50, 255, 255, 255]
     ]
     If this collection was added to args.outputs.solids, two solids would be output
     next to each other, one black and one white.
     Nested arrays can be used in collections, as you will see in this sample app.
  
   Reminders:
  
   - args.outputs.solids: An array. The values generate a solid.
     The parameters for a solid are
     1. The position on the screen (x, y)
     2. The width (w)
     3. The height (h)
     4. The color (r, g, b) (if a color is not assigned, the object's default color will be black)
     NOTE: THE PARAMETERS ARE THE SAME FOR BORDERS!
  
     Here is an example of a (red) border or solid definition:
     [100, 100, 400, 500, 255, 0, 0]
     It will be a solid or border depending on if it is added to args.outputs.solids or args.outputs.borders.
     For more information about solids and borders, go to mygame/documentation/03-solids-and-borders.md.
  
   - args.outputs.sprites: An array. The values generate a sprite.
     The parameters for sprites are
     1. The position on the screen (x, y)
     2. The width (w)
     3. The height (h)
     4. The image path (p)
  
     Here is an example of a sprite definition:
     [100, 100, 400, 500, 'sprites/dragonruby.png']
     For more information about sprites, go to mygame/documentation/05-sprites.md.
  
  =end
  
  # This code demonstrates the creation and output of objects like sprites, borders, and solids
  # If filled in, they are solids
  # If hollow, they are borders
  # If images, they are sprites
  
  # Solids are added to args.outputs.solids
  # Borders are added to args.outputs.borders
  # Sprites are added to args.outputs.sprites
  
  # The tick method runs 60 frames every second.
  # Your game is going to happen under this one function.
  def tick args
    border_as_solid_and_solid_as_border args
    sprite_as_border_or_solids args
    collection_of_borders_and_solids args
    collection_of_sprites args
  end
  
  # Shows a border being output onto the screen as a border and a solid
  # Also shows how colors can be set
  def border_as_solid_and_solid_as_border args
    border = [0, 0, 50, 50]
    args.outputs.borders << border
    args.outputs.solids  << border
  
    # Red, green, blue saturations (last three parameters) can be any number between 0 and 255
    border_with_color = [0, 100, 50, 50, 255, 0, 0]
    args.outputs.borders << border_with_color
    args.outputs.solids  << border_with_color
  
    border_with_nested_color = [0, 200, 50, 50, [0, 255, 0]] # nested color
    args.outputs.borders << border_with_nested_color
    args.outputs.solids  << border_with_nested_color
  
    border_with_nested_rect = [[0, 300, 50, 50], 0, 0, 255] # nested rect
    args.outputs.borders << border_with_nested_rect
    args.outputs.solids  << border_with_nested_rect
  
    border_with_nested_color_and_rect = [[0, 400, 50, 50], [255, 0, 255]] # nested rect and color
    args.outputs.borders << border_with_nested_color_and_rect
    args.outputs.solids  << border_with_nested_color_and_rect
  end
  
  # Shows a sprite output onto the screen as a sprite, border, and solid
  # Demonstrates that all three outputs appear differently on screen
  def sprite_as_border_or_solids args
    sprite = [100, 0, 50, 50, 'sprites/ship.png']
    args.outputs.sprites << sprite
  
    # Sprite_as_border variable has same parameters (excluding position) as above object,
    # but will appear differently on screen because it is added to args.outputs.borders
    sprite_as_border = [100, 100, 50, 50, 'sprites/ship.png']
    args.outputs.borders << sprite_as_border
  
    # Sprite_as_solid variable has same parameters (excluding position) as above object,
    # but will appear differently on screen because it is added to args.outputs.solids
    sprite_as_solid = [100, 200, 50, 50, 'sprites/ship.png']
    args.outputs.solids << sprite_as_solid
  end
  
  # Holds and outputs a collection of borders and a collection of solids
  # Collections are created by using arrays to hold parameters of each individual object
  def collection_of_borders_and_solids args
    collection_borders = [
      [
        [200,  0, 50, 50],                    # black border
        [200,  100, 50, 50, 255, 0, 0],       # red border
        [200,  200, 50, 50, [0, 255, 0]],     # nested color
      ],
      [[200, 300, 50, 50], 0, 0, 255],        # nested rect
      [[200, 400, 50, 50], [255, 0, 255]]     # nested rect and nested color
    ]
  
    args.outputs.borders << collection_borders
  
    collection_solids = [
      [
        [[300, 300, 50, 50], 0, 0, 255],      # nested rect
        [[300, 400, 50, 50], [255, 0, 255]]   # nested rect and nested color
      ],
      [300,  0, 50, 50],
      [300,  100, 50, 50, 255, 0, 0],
      [300,  200, 50, 50, [0, 255, 0]],       # nested color
    ]
  
    args.outputs.solids << collection_solids
  end
  
  # Holds and outputs a collection of sprites by adding it to args.outputs.sprites
  # Also outputs a collection with same parameters (excluding position) by adding
  # it to args.outputs.solids and another to args.outputs.borders
  def collection_of_sprites args
    sprites_collection = [
      [
        [400, 0, 50, 50, 'sprites/ship.png'],
        [400, 100, 50, 50, 'sprites/ship.png'],
      ],
      [400, 200, 50, 50, 'sprites/ship.png']
    ]
  
    args.outputs.sprites << sprites_collection
  
    args.outputs.solids << [
      [500, 0, 50, 50, 'sprites/ship.png'],
      [500, 100, 50, 50, 'sprites/ship.png'],
      [[[500, 200, 50, 50, 'sprites/ship.png']]]
    ]
  
    args.outputs.borders << [
      [
        [600, 0, 50, 50, 'sprites/ship.png'],
        [600, 100, 50, 50, 'sprites/ship.png'],
      ],
      [600, 200, 50, 50, 'sprites/ship.png']
    ]
  end

#+end_src

*** Advanced Rendering - Render Primitives As Hash - main.rb
#+begin_src ruby
  # ./samples/07_advanced_rendering/05_render_primitives_as_hash/app/main.rb
  =begin
  
   Reminders:
  
   - Hashes: Collection of unique keys and their corresponding values. The value can be found
     using their keys.
  
     For example, if we have a "numbers" hash that stores numbers in English as the
     key and numbers in Spanish as the value, we'd have a hash that looks like this...
     numbers = { "one" => "uno", "two" => "dos", "three" => "tres" }
     and on it goes.
  
     Now if we wanted to find the corresponding value of the "one" key, we could say
     puts numbers["one"]
     which would print "uno" to the console.
  
   - args.outputs.sprites: An array. The values generate a sprite.
     The parameters are [X, Y, WIDTH, HEIGHT, PATH, ANGLE, ALPHA, RED, GREEN, BLUE]
     For more information about sprites, go to mygame/documentation/05-sprites.md.
  
   - args.outputs.labels: An array. The values generate a label.
     The parameters are [X, Y, TEXT, SIZE, ALIGNMENT, RED, GREEN, BLUE, ALPHA, FONT STYLE]
     For more information about labels, go to mygame/documentation/02-labels.md.
  
   - args.outputs.solids: An array. The values generate a solid.
     The parameters are [X, Y, WIDTH, HEIGHT, RED, GREEN, BLUE, ALPHA]
     For more information about solids, go to mygame/documentation/03-solids-and-borders.md.
  
   - args.outputs.borders: An array. The values generate a border.
     The parameters are the same as a solid.
     For more information about borders, go to mygame/documentation/03-solids-and-borders.md.
  
   - args.outputs.lines: An array. The values generate a line.
     The parameters are [X1, Y1, X2, Y2, RED, GREEN, BLUE]
     For more information about labels, go to mygame/documentation/02-labels.md.
  
  =end
  
  # This sample app demonstrates how hashes can be used to output different kinds of objects.
  
  def tick args
    args.state.angle ||= 0 # initializes angle to 0
    args.state.angle  += 1 # increments angle by 1 every frame (60 times a second)
  
    # Outputs sprite using a hash
    args.outputs.sprites << {
      x: 30,                          # sprite position
      y: 550,
      w: 128,                         # sprite size
      h: 101,
      path: "dragonruby.png",         # image path
      angle: args.state.angle,        # angle
      a: 255,                         # alpha (transparency)
      r: 255,                         # color saturation
      g: 255,
      b: 255,
      tile_x:  0,                     # sprite sub division/tile
      tile_y:  0,
      tile_w: -1,
      tile_h: -1,
      flip_vertically: false,         # don't flip sprite
      flip_horizontally: false,
      angle_anchor_x: 0.5,            # rotation center set to middle
      angle_anchor_y: 0.5
    }
  
    # Outputs label using a hash
    args.outputs.labels << {
      x:              200,                 # label position
      y:              550,
      text:           "dragonruby",        # label text
      size_enum:      2,
      alignment_enum: 1,
      r:              155,                 # color saturation
      g:              50,
      b:              50,
      a:              255,                 # transparency
      font:           "fonts/manaspc.ttf"  # font style; without mentioned file, label won't output correctly
    }
  
    # Outputs solid using a hash
    # [X, Y, WIDTH, HEIGHT, RED, GREEN, BLUE, ALPHA]
    args.outputs.solids << {
      x: 400,                         # position
      y: 550,
      w: 160,                         # size
      h:  90,
      r: 120,                         # color saturation
      g:  50,
      b:  50,
      a: 255                          # transparency
    }
  
    # Outputs border using a hash
    # Same parameters as a solid
    args.outputs.borders << {
      x: 600,
      y: 550,
      w: 160,
      h:  90,
      r: 120,
      g:  50,
      b:  50,
      a: 255
    }
  
    # Outputs line using a hash
    args.outputs.lines << {
      x:  900,                        # starting position
      y:  550,
      x2: 1200,                       # ending position
      y2: 550,
      r:  120,                        # color saturation
      g:   50,
      b:   50,
      a:  255                         # transparency
    }
  
    # Outputs sprite as a primitive using a hash
    args.outputs.primitives << {
      x: 30,                          # position
      y: 200,
      w: 128,                         # size
      h: 101,
      path: "dragonruby.png",         # image path
      angle: args.state.angle,        # angle
      a: 255,                         # transparency
      r: 255,                         # color saturation
      g: 255,
      b: 255,
      tile_x:  0,                     # sprite sub division/tile
      tile_y:  0,
      tile_w: -1,
      tile_h: -1,
      flip_vertically: false,         # don't flip
      flip_horizontally: false,
      angle_anchor_x: 0.5,            # rotation center set to middle
      angle_anchor_y: 0.5
    }.sprite!
  
    # Outputs label as primitive using a hash
    args.outputs.primitives << {
      x:         200,                 # position
      y:         200,
      text:      "dragonruby",        # text
      size:      2,
      alignment: 1,
      r:         155,                 # color saturation
      g:         50,
      b:         50,
      a:         255,                 # transparency
      font:      "fonts/manaspc.ttf"  # font style
    }.label!
  
    # Outputs solid as primitive using a hash
    args.outputs.primitives << {
      x: 400,                         # position
      y: 200,
      w: 160,                         # size
      h:  90,
      r: 120,                         # color saturation
      g:  50,
      b:  50,
      a: 255                          # transparency
    }.solid!
  
    # Outputs border as primitive using a hash
    # Same parameters as solid
    args.outputs.primitives << {
      x: 600,                         # position
      y: 200,
      w: 160,                         # size
      h:  90,
      r: 120,                         # color saturation
      g:  50,
      b:  50,
      a: 255                          # transparency
    }.border!
  
    # Outputs line as primitive using a hash
    args.outputs.primitives << {
      x:  900,                        # starting position
      y:  200,
      x2: 1200,                       # ending position
      y2: 200,
      r:  120,                        # color saturation
      g:   50,
      b:   50,
      a:  255                         # transparency
    }.line!
  end

#+end_src

*** Advanced Rendering - Pixel Arrays - main.rb
#+begin_src ruby
  # ./samples/07_advanced_rendering/06_pixel_arrays/app/main.rb
  $gtk.reset
  
  def tick args
    args.state.posinc ||= 1
    args.state.pos ||= 0
    args.state.rotation ||= 0
  
    dimension = 10  # keep it small and let the GPU scale it when rendering the sprite.
  
    # Set up our "scanner" pixel array and fill it with black pixels.
    args.pixel_array(:scanner).width = dimension
    args.pixel_array(:scanner).height = dimension
    args.pixel_array(:scanner).pixels.fill(0xFF000000, 0, dimension * dimension)  # black, full alpha
  
    # Draw a green line that bounces up and down the sprite.
    args.pixel_array(:scanner).pixels.fill(0xFF00FF00, dimension * args.state.pos, dimension)  # green, full alpha
  
    # Adjust position for next frame.
    args.state.pos += args.state.posinc
    if args.state.posinc > 0 && args.state.pos >= dimension
      args.state.posinc = -1
      args.state.pos = dimension - 1
    elsif args.state.posinc < 0 && args.state.pos < 0
      args.state.posinc = 1
      args.state.pos = 1
    end
  
    # New/changed pixel arrays get uploaded to the GPU before we render
    #  anything. At that point, they can be scaled, rotated, and otherwise
    #  used like any other sprite.
    w = 100
    h = 100
    x = (1280 - w) / 2
    y = (720 - h) / 2
    args.outputs.background_color = [64, 0, 128]
    args.outputs.primitives << [x, y, w, h, :scanner, args.state.rotation].sprite
    args.state.rotation += 1
  
    args.outputs.primitives << args.gtk.current_framerate_primitives
  end
  

#+end_src

*** Advanced Rendering - Simple Camera - main.rb
#+begin_src ruby
  # ./samples/07_advanced_rendering/07_simple_camera/app/main.rb
  def tick args
    # variables you can play around with
    args.state.world.w      ||= 1280
    args.state.world.h      ||= 720
  
    args.state.player.x     ||= 0
    args.state.player.y     ||= 0
    args.state.player.size  ||= 32
  
    args.state.enemy.x      ||= 700
    args.state.enemy.y      ||= 700
    args.state.enemy.size   ||= 16
  
    args.state.camera.x                ||= 640
    args.state.camera.y                ||= 300
    args.state.camera.scale            ||= 1.0
    args.state.camera.show_empty_space ||= :yes
  
    # instructions
    args.outputs.primitives << { x: 0, y:  80.from_top, w: 360, h: 80, r: 0, g: 0, b: 0, a: 128 }.solid!
    args.outputs.primitives << { x: 10, y: 10.from_top, text: "arrow keys to move around", r: 255, g: 255, b: 255}.label!
    args.outputs.primitives << { x: 10, y: 30.from_top, text: "+/- to change zoom of camera", r: 255, g: 255, b: 255}.label!
    args.outputs.primitives << { x: 10, y: 50.from_top, text: "tab to change camera edge behavior", r: 255, g: 255, b: 255}.label!
  
    # render scene
    args.outputs[:scene].w = args.state.world.w
    args.outputs[:scene].h = args.state.world.h
  
    args.outputs[:scene].solids << { x: 0, y: 0, w: args.state.world.w, h: args.state.world.h, r: 20, g: 60, b: 80 }
    args.outputs[:scene].solids << { x: args.state.player.x, y: args.state.player.y,
                                     w: args.state.player.size, h: args.state.player.size, r: 80, g: 155, b: 80 }
    args.outputs[:scene].solids << { x: args.state.enemy.x, y: args.state.enemy.y,
                                     w: args.state.enemy.size, h: args.state.enemy.size, r: 155, g: 80, b: 80 }
  
    # render camera
    scene_position = calc_scene_position args
    args.outputs.sprites << { x: scene_position.x,
                              y: scene_position.y,
                              w: scene_position.w,
                              h: scene_position.h,
                              path: :scene }
  
    # move player
    if args.inputs.directional_angle
      args.state.player.x += args.inputs.directional_angle.vector_x * 5
      args.state.player.y += args.inputs.directional_angle.vector_y * 5
      args.state.player.x  = args.state.player.x.clamp(0, args.state.world.w - args.state.player.size)
      args.state.player.y  = args.state.player.y.clamp(0, args.state.world.h - args.state.player.size)
    end
  
    # +/- to zoom in and out
    if args.inputs.keyboard.plus && args.state.tick_count.zmod?(3)
      args.state.camera.scale += 0.05
    elsif args.inputs.keyboard.hyphen && args.state.tick_count.zmod?(3)
      args.state.camera.scale -= 0.05
    elsif args.inputs.keyboard.key_down.tab
      if args.state.camera.show_empty_space == :yes
        args.state.camera.show_empty_space = :no
      else
        args.state.camera.show_empty_space = :yes
      end
    end
  
    args.state.camera.scale = args.state.camera.scale.greater(0.1)
  end
  
  def calc_scene_position args
    result = { x: args.state.camera.x - (args.state.player.x * args.state.camera.scale),
               y: args.state.camera.y - (args.state.player.y * args.state.camera.scale),
               w: args.state.world.w * args.state.camera.scale,
               h: args.state.world.h * args.state.camera.scale,
               scale: args.state.camera.scale }
  
    return result if args.state.camera.show_empty_space == :yes
  
    if result.w < args.grid.w
      result.merge!(x: (args.grid.w - result.w).half)
    elsif (args.state.player.x * result.scale) < args.grid.w.half
      result.merge!(x: 10)
    elsif (result.x + result.w) < args.grid.w
      result.merge!(x: - result.w + (args.grid.w - 10))
    end
  
    if result.h < args.grid.h
      result.merge!(y: (args.grid.h - result.h).half)
    elsif (result.y) > 10
      result.merge!(y: 10)
    elsif (result.y + result.h) < args.grid.h
      result.merge!(y: - result.h + (args.grid.h - 10))
    end
  
    result
  end

#+end_src

*** Advanced Rendering - Splitscreen Camera - main.rb
#+begin_src ruby
  # ./samples/07_advanced_rendering/08_splitscreen_camera/app/main.rb
  class CameraMovement
    attr_accessor :state, :inputs, :outputs, :grid
  
    #==============================================================================================
    #Serialize
    def serialize
      {state: state, inputs: inputs, outputs: outputs, grid: grid }
    end
  
    def inspect
      serialize.to_s
    end
  
    def to_s
      serialize.to_s
    end
  
    #==============================================================================================
    #Tick
    def tick
      defaults
      calc
      render
      input
    end
  
    #==============================================================================================
    #Default functions
    def defaults
      outputs[:scene].background_color = [0,0,0]
      state.trauma ||= 0.0
      state.trauma_power ||= 2
      state.player_cyan ||= new_player_cyan
      state.player_magenta ||= new_player_magenta
      state.camera_magenta ||= new_camera_magenta
      state.camera_cyan ||= new_camera_cyan
      state.camera_center ||= new_camera_center
      state.room ||= new_room
    end
  
    def default_player x, y, w, h, sprite_path
      state.new_entity(:player,
                       { x: x,
                         y: y,
                         dy: 0,
                         dx: 0,
                         w: w,
                         h: h,
                         damage: 0,
                         dead: false,
                         orientation: "down",
                         max_alpha: 255,
                         sprite_path: sprite_path})
    end
  
    def default_floor_tile x, y, w, h, sprite_path
      state.new_entity(:room,
                       { x: x,
                         y: y,
                         w: w,
                         h: h,
                         sprite_path: sprite_path})
    end
  
    def default_camera x, y, w, h
      state.new_entity(:camera,
                       { x: x,
                         y: y,
                         dx: 0,
                         dy: 0,
                         w: w,
                         h: h})
    end
  
    def new_player_cyan
      default_player(0, 0, 64, 64,
                     "sprites/player/player_#{state.player_cyan.orientation}_standing.png")
    end
  
    def new_player_magenta
      default_player(64, 0, 64, 64,
                     "sprites/player/player_#{state.player_magenta.orientation}_standing.png")
    end
  
    def new_camera_magenta
      default_camera(0,0,720,720)
    end
  
    def new_camera_cyan
      default_camera(0,0,720,720)
    end
  
    def new_camera_center
      default_camera(0,0,1280,720)
    end
  
  
    def new_room
      default_floor_tile(0,0,1024,1024,'sprites/rooms/camera_room.png')
    end
  
    #==============================================================================================
    #Calculation functions
    def calc
      calc_camera_magenta
      calc_camera_cyan
      calc_camera_center
      calc_player_cyan
      calc_player_magenta
      calc_trauma_decay
    end
  
    def center_camera_tolerance
      return Math.sqrt(((state.player_magenta.x - state.player_cyan.x) ** 2) +
                ((state.player_magenta.y - state.player_cyan.y) ** 2)) > 640
    end
  
    def calc_player_cyan
      state.player_cyan.x += state.player_cyan.dx
      state.player_cyan.y += state.player_cyan.dy
    end
  
    def calc_player_magenta
      state.player_magenta.x += state.player_magenta.dx
      state.player_magenta.y += state.player_magenta.dy
    end
  
    def calc_camera_center
      timeScale = 1
      midX = (state.player_magenta.x + state.player_cyan.x)/2
      midY = (state.player_magenta.y + state.player_cyan.y)/2
      targetX = midX - state.camera_center.w/2
      targetY = midY - state.camera_center.h/2
      state.camera_center.x += (targetX - state.camera_center.x) * 0.1 * timeScale
      state.camera_center.y += (targetY - state.camera_center.y) * 0.1 * timeScale
    end
  
  
    def calc_camera_magenta
      timeScale = 1
      targetX = state.player_magenta.x + state.player_magenta.w - state.camera_magenta.w/2
      targetY = state.player_magenta.y + state.player_magenta.h - state.camera_magenta.h/2
      state.camera_magenta.x += (targetX - state.camera_magenta.x) * 0.1 * timeScale
      state.camera_magenta.y += (targetY - state.camera_magenta.y) * 0.1 * timeScale
    end
  
    def calc_camera_cyan
      timeScale = 1
      targetX = state.player_cyan.x + state.player_cyan.w - state.camera_cyan.w/2
      targetY = state.player_cyan.y + state.player_cyan.h - state.camera_cyan.h/2
      state.camera_cyan.x += (targetX - state.camera_cyan.x) * 0.1 * timeScale
      state.camera_cyan.y += (targetY - state.camera_cyan.y) * 0.1 * timeScale
    end
  
    def calc_player_quadrant angle
      if angle < 45 and angle > -45 and state.player_cyan.x < state.player_magenta.x
        return 1
      elsif angle < 45 and angle > -45 and state.player_cyan.x > state.player_magenta.x
        return 3
      elsif (angle > 45 or angle < -45) and state.player_cyan.y < state.player_magenta.y
        return 2
      elsif (angle > 45 or angle < -45) and state.player_cyan.y > state.player_magenta.y
        return 4
      end
    end
  
    def calc_camera_shake
      state.trauma
    end
  
    def calc_trauma_decay
      state.trauma = state.trauma * 0.9
    end
  
    def calc_random_float_range(min, max)
      rand * (max-min) + min
    end
  
    #==============================================================================================
    #Render Functions
    def render
      render_floor
      render_player_cyan
      render_player_magenta
      if center_camera_tolerance
        render_split_camera_scene
      else
        render_camera_center_scene
      end
    end
  
    def render_player_cyan
      outputs[:scene].sprites << {x: state.player_cyan.x,
                                  y: state.player_cyan.y,
                                  w: state.player_cyan.w,
                                  h: state.player_cyan.h,
                                  path: "sprites/player/player_#{state.player_cyan.orientation}_standing.png",
                                  r: 0,
                                  g: 255,
                                  b: 255}
    end
  
    def render_player_magenta
      outputs[:scene].sprites << {x: state.player_magenta.x,
                                  y: state.player_magenta.y,
                                  w: state.player_magenta.w,
                                  h: state.player_magenta.h,
                                  path: "sprites/player/player_#{state.player_magenta.orientation}_standing.png",
                                  r: 255,
                                  g: 0,
                                  b: 255}
    end
  
    def render_floor
      outputs[:scene].sprites << [state.room.x, state.room.y,
                                  state.room.w, state.room.h,
                                  state.room.sprite_path]
    end
  
    def render_camera_center_scene
      zoomFactor = 1
      outputs[:scene].width = state.room.w
      outputs[:scene].height = state.room.h
  
      maxAngle = 10.0
      maxOffset = 20.0
      angle = maxAngle * calc_camera_shake * calc_random_float_range(-1,1)
      offsetX = 32 - (maxOffset * calc_camera_shake * calc_random_float_range(-1,1))
      offsetY = 32 - (maxOffset * calc_camera_shake * calc_random_float_range(-1,1))
  
      outputs.sprites << {x: (-state.camera_center.x - offsetX)/zoomFactor,
                          y: (-state.camera_center.y - offsetY)/zoomFactor,
                          w: outputs[:scene].width/zoomFactor,
                          h: outputs[:scene].height/zoomFactor,
                          path: :scene,
                          angle: angle,
                          source_w: -1,
                          source_h: -1}
      outputs.labels << [128,64,"#{state.trauma.round(1)}",8,2,255,0,255,255]
    end
  
    def render_split_camera_scene
       outputs[:scene].width = state.room.w
       outputs[:scene].height = state.room.h
       render_camera_magenta_scene
       render_camera_cyan_scene
  
       angle = Math.atan((state.player_magenta.y - state.player_cyan.y)/(state.player_magenta.x- state.player_cyan.x)) * 180/Math::PI
       output_split_camera angle
  
    end
  
    def render_camera_magenta_scene
       zoomFactor = 1
       offsetX = 32
       offsetY = 32
  
       outputs[:scene_magenta].sprites << {x: (-state.camera_magenta.x*2),
                                           y: (-state.camera_magenta.y),
                                           w: outputs[:scene].width*2,
                                           h: outputs[:scene].height,
                                           path: :scene}
  
    end
  
    def render_camera_cyan_scene
      zoomFactor = 1
      offsetX = 32
      offsetY = 32
      outputs[:scene_cyan].sprites << {x: (-state.camera_cyan.x*2),
                                       y: (-state.camera_cyan.y),
                                       w: outputs[:scene].width*2,
                                       h: outputs[:scene].height,
                                       path: :scene}
    end
  
    def output_split_camera angle
      #TODO: Clean this up!
      quadrant = calc_player_quadrant angle
      outputs.labels << [128,64,"#{quadrant}",8,2,255,0,255,255]
      if quadrant == 1
        set_camera_attributes(w: 640, h: 720, m_x: 640, m_y: 0, c_x: 0, c_y: 0)
  
      elsif quadrant == 2
        set_camera_attributes(w: 1280, h: 360, m_x: 0, m_y: 360, c_x: 0, c_y: 0)
  
      elsif quadrant == 3
        set_camera_attributes(w: 640, h: 720, m_x: 0, m_y: 0, c_x: 640, c_y: 0)
  
      elsif quadrant == 4
        set_camera_attributes(w: 1280, h: 360, m_x: 0, m_y: 0, c_x: 0, c_y: 360)
  
      end
    end
  
    def set_camera_attributes(w: 0, h: 0, m_x: 0, m_y: 0, c_x: 0, c_y: 0)
      state.camera_cyan.w = w + 64
      state.camera_cyan.h = h + 64
      outputs[:scene_cyan].width = (w) * 2
      outputs[:scene_cyan].height = h
  
      state.camera_magenta.w = w + 64
      state.camera_magenta.h = h + 64
      outputs[:scene_magenta].width = (w) * 2
      outputs[:scene_magenta].height = h
      outputs.sprites << {x: m_x,
                          y: m_y,
                          w: w,
                          h: h,
                          path: :scene_magenta}
      outputs.sprites << {x: c_x,
                          y: c_y,
                          w: w,
                          h: h,
                          path: :scene_cyan}
    end
  
    def add_trauma amount
      state.trauma = [state.trauma + amount, 1.0].min
    end
  
    def remove_trauma amount
      state.trauma = [state.trauma - amount, 0.0].max
    end
    #==============================================================================================
    #Input functions
    def input
      input_move_cyan
      input_move_magenta
  
      if inputs.keyboard.key_down.t
        add_trauma(0.5)
      elsif inputs.keyboard.key_down.y
        remove_trauma(0.1)
      end
    end
  
    def input_move_cyan
      if inputs.keyboard.key_held.up
        state.player_cyan.dy = 5
        state.player_cyan.orientation = "up"
      elsif inputs.keyboard.key_held.down
        state.player_cyan.dy = -5
        state.player_cyan.orientation = "down"
      else
        state.player_cyan.dy *= 0.8
      end
      if inputs.keyboard.key_held.left
        state.player_cyan.dx = -5
        state.player_cyan.orientation = "left"
      elsif inputs.keyboard.key_held.right
        state.player_cyan.dx = 5
        state.player_cyan.orientation = "right"
      else
        state.player_cyan.dx *= 0.8
      end
  
      outputs.labels << [128,512,"#{state.player_cyan.x.round()}",8,2,0,255,255,255]
      outputs.labels << [128,480,"#{state.player_cyan.y.round()}",8,2,0,255,255,255]
    end
  
    def input_move_magenta
      if inputs.keyboard.key_held.w
        state.player_magenta.dy = 5
        state.player_magenta.orientation = "up"
      elsif inputs.keyboard.key_held.s
        state.player_magenta.dy = -5
        state.player_magenta.orientation = "down"
      else
        state.player_magenta.dy *= 0.8
      end
      if inputs.keyboard.key_held.a
        state.player_magenta.dx = -5
        state.player_magenta.orientation = "left"
      elsif inputs.keyboard.key_held.d
        state.player_magenta.dx = 5
        state.player_magenta.orientation = "right"
      else
        state.player_magenta.dx *= 0.8
      end
  
      outputs.labels << [128,360,"#{state.player_magenta.x.round()}",8,2,255,0,255,255]
      outputs.labels << [128,328,"#{state.player_magenta.y.round()}",8,2,255,0,255,255]
    end
  end
  
  $camera_movement = CameraMovement.new
  
  def tick args
    args.outputs.background_color = [0,0,0]
    $camera_movement.inputs  = args.inputs
    $camera_movement.outputs = args.outputs
    $camera_movement.state   = args.state
    $camera_movement.grid    = args.grid
    $camera_movement.tick
  end

#+end_src

*** Advanced Rendering - Z Targeting Camera - main.rb
#+begin_src ruby
  # ./samples/07_advanced_rendering/09_z_targeting_camera/app/main.rb
  class Game
    attr_gtk
  
    def tick
      defaults
      render
      input
      calc
    end
  
    def defaults
      outputs.background_color = [219, 208, 191]
      player.x        ||= 634
      player.y        ||= 153
      player.angle    ||= 90
      player.distance ||= arena_radius
      target.x        ||= 634
      target.y        ||= 359
    end
  
    def render
      outputs[:scene].sprites << ([0, 0, 933, 700, 'sprites/arena.png'].center_inside_rect grid.rect)
      outputs[:scene].sprites << target_sprite
      outputs[:scene].sprites << player_sprite
      outputs.sprites << scene
    end
  
    def target_sprite
      {
        x: target.x, y: target.y,
        w: 10, h: 10,
        path: 'sprites/square/black.png'
      }.anchor_rect 0.5, 0.5
    end
  
    def input
      if inputs.up && player.distance > 30
        player.distance -= 2
      elsif inputs.down && player.distance < 200
        player.distance += 2
      end
  
      player.angle += inputs.left_right * -1
    end
  
    def calc
      player.x = target.x + ((player.angle *  1).vector_x player.distance)
      player.y = target.y + ((player.angle * -1).vector_y player.distance)
    end
  
    def player_sprite
      {
        x: player.x,
        y: player.y,
        w: 50,
        h: 100,
        path: 'sprites/player.png',
        angle: (player.angle * -1) + 90
      }.anchor_rect 0.5, 0
    end
  
    def center_map
      { x: 634, y: 359 }
    end
  
    def zoom_factor_single
      2 - ((args.geometry.distance player, center_map).fdiv arena_radius)
    end
  
    def zoom_factor
      zoom_factor_single ** 2
    end
  
    def arena_radius
      206
    end
  
    def scene
      {
        x:    (640 - player.x) + (640 - (640 * zoom_factor)),
        y:    (360 - player.y - (75 * zoom_factor)) + (320 - (320 * zoom_factor)),
        w:    1280 * zoom_factor,
        h:     720 * zoom_factor,
        path: :scene,
        angle: player.angle - 90,
        angle_anchor_x: (player.x.fdiv 1280),
        angle_anchor_y: (player.y.fdiv 720)
      }
    end
  
    def player
      state.player
    end
  
    def target
      state.target
    end
  end
  
  def tick args
    $game ||= Game.new
    $game.args = args
    $game.tick
  end
  
  $gtk.reset

#+end_src

*** Advanced Rendering - Blend Modes - main.rb
#+begin_src ruby
  # ./samples/07_advanced_rendering/10_blend_modes/app/main.rb
  $gtk.reset
  
  def draw_blendmode args, mode
    w = 160
    h = w
    args.state.x += (1280-w) / (args.state.blendmodes.length + 1)
    x = args.state.x
    y = (720 - h) / 2
    s = 'sprites/blue-feathered.png'
    args.outputs.sprites << { blendmode_enum: mode.value, x: x, y: y, w: w, h: h, path: s }
    args.outputs.labels << [x + (w/2), y, mode.name.to_s, 1, 1, 255, 255, 255]
  end
  
  def tick args
  
    # Different blend modes do different things, depending on what they
    # blend against (in this case, the pixels of the background color).
    args.state.bg_element ||= 1
    args.state.bg_color ||= 255
    args.state.bg_color_direction ||= 1
    bg_r = (args.state.bg_element == 1) ? args.state.bg_color : 0
    bg_g = (args.state.bg_element == 2) ? args.state.bg_color : 0
    bg_b = (args.state.bg_element == 3) ? args.state.bg_color : 0
    args.state.bg_color += args.state.bg_color_direction
    if (args.state.bg_color_direction > 0) && (args.state.bg_color >= 255)
      args.state.bg_color_direction = -1
      args.state.bg_color = 255
    elsif (args.state.bg_color_direction < 0) && (args.state.bg_color <= 0)
      args.state.bg_color_direction = 1
      args.state.bg_color = 0
      args.state.bg_element += 1
      if args.state.bg_element >= 4
        args.state.bg_element = 1
      end
    end
  
    args.outputs.background_color = [ bg_r, bg_g, bg_b, 255 ]
  
    args.state.blendmodes ||= [
      { name: :none,  value: 0 },
      { name: :blend, value: 1 },
      { name: :add,   value: 2 },
      { name: :mod,   value: 3 },
      { name: :mul,   value: 4 }
    ]
  
    args.state.x = 0  # reset this, draw_blendmode will increment it.
    args.state.blendmodes.each { |blendmode| draw_blendmode args, blendmode }
  end

#+end_src

*** Advanced Rendering - Render Target Noclear - main.rb
#+begin_src ruby
  # ./samples/07_advanced_rendering/11_render_target_noclear/app/main.rb
  def tick args
    args.state.x ||= 500
    args.state.y ||= 350
    args.state.xinc ||= 7
    args.state.yinc ||= 7
    args.state.bgcolor ||= 1
    args.state.bginc ||= 1
  
    # clear the render target on the first tick, and then never again. Draw
    #  another box to it every tick, accumulating over time.
    clear_target = (args.state.tick_count == 0) || (args.inputs.keyboard.key_down.space)
    args.render_target(:accumulation).background_color = [ 0, 0, 0, 0 ];
    args.render_target(:accumulation).clear_before_render = clear_target
    args.render_target(:accumulation).solids << [args.state.x, args.state.y, 25, 25, 255, 0, 0, 255];
    args.state.x += args.state.xinc
    args.state.y += args.state.yinc
    args.state.bgcolor += args.state.bginc
  
    # animation upkeep...change where we draw the next box and what color the
    #  window background will be.
    if args.state.xinc > 0 && args.state.x >= 1280
      args.state.xinc = -7
    elsif args.state.xinc < 0 && args.state.x < 0
      args.state.xinc = 7
    end
  
    if args.state.yinc > 0 && args.state.y >= 720
      args.state.yinc = -7
    elsif args.state.yinc < 0 && args.state.y < 0
      args.state.yinc = 7
    end
  
    if args.state.bginc > 0 && args.state.bgcolor >= 255
      args.state.bginc = -1
    elsif args.state.bginc < 0 && args.state.bgcolor <= 0
      args.state.bginc = 1
    end
  
    # clear the screen to a shade of blue and draw the render target, which
    #  is not clearing every frame, on top of it. Note that you can NOT opt to
    #  skip clearing the screen, only render targets. The screen clears every
    #  frame; double-buffering would prevent correct updates between frames.
    args.outputs.background_color = [ 0, 0, args.state.bgcolor, 255 ]
    args.outputs.sprites << [ 0, 0, 1280, 720, :accumulation ]
  end
  
  $gtk.reset

#+end_src

*** Advanced Rendering - Lighting - main.rb
#+begin_src ruby
  # ./samples/07_advanced_rendering/12_lighting/app/main.rb
  def calc args
    args.state.swinging_light_sign     ||= 1
    args.state.swinging_light_start_at ||= 0
    args.state.swinging_light_duration ||= 300
    args.state.swinging_light_perc       = args.state
                                               .swinging_light_start_at
                                               .ease_spline_extended args.state.tick_count,
                                                                     args.state.swinging_light_duration,
                                                                     [
                                                                       [0.0, 1.0, 1.0, 1.0],
                                                                       [1.0, 1.0, 1.0, 0.0]
                                                                     ]
    args.state.max_swing_angle ||= 45
  
    if args.state.swinging_light_start_at.elapsed_time > args.state.swinging_light_duration
      args.state.swinging_light_start_at = args.state.tick_count
      args.state.swinging_light_sign *= -1
    end
  
    args.state.swinging_light_angle = 360 + ((args.state.max_swing_angle * args.state.swinging_light_perc) * args.state.swinging_light_sign)
  end
  
  def render args
    args.outputs.background_color = [0, 0, 0]
  
    # render scene
    args.outputs[:scene].sprites << { x:        0, y:   0, w: 1280, h: 720, path: :pixel }
    args.outputs[:scene].sprites << { x: 640 - 40, y: 100, w:   80, h:  80, path: 'sprites/square/blue.png' }
    args.outputs[:scene].sprites << { x: 640 - 40, y: 200, w:   80, h:  80, path: 'sprites/square/blue.png' }
    args.outputs[:scene].sprites << { x: 640 - 40, y: 300, w:   80, h:  80, path: 'sprites/square/blue.png' }
    args.outputs[:scene].sprites << { x: 640 - 40, y: 400, w:   80, h:  80, path: 'sprites/square/blue.png' }
    args.outputs[:scene].sprites << { x: 640 - 40, y: 500, w:   80, h:  80, path: 'sprites/square/blue.png' }
  
    # render light
    swinging_light_w = 1100
    args.outputs[:lights].background_color = [0, 0, 0, 0]
    args.outputs[:lights].sprites << { x: 640 - swinging_light_w.half,
                                       y: -1300,
                                       w: swinging_light_w,
                                       h: 3000,
                                       angle_anchor_x: 0.5,
                                       angle_anchor_y: 1.0,
                                       path: "sprites/lights/mask.png",
                                       angle: args.state.swinging_light_angle }
  
    args.outputs[:lights].sprites << { x: args.inputs.mouse.x - 400,
                                       y: args.inputs.mouse.y - 400,
                                       w: 800,
                                       h: 800,
                                       path: "sprites/lights/mask.png" }
  
    # merge unlighted scene with lights
    args.outputs[:lighted_scene].sprites << { x: 0, y: 0, w: 1280, h: 720, path: :lights, blendmode_enum: 0 }
    args.outputs[:lighted_scene].sprites << { blendmode_enum: 2, x: 0, y: 0, w: 1280, h: 720, path: :scene }
  
    # output lighted scene to main canvas
    args.outputs.sprites << { x: 0, y: 0, w: 1280, h: 720, path: :lighted_scene }
  
    # render lights and scene render_targets as a mini map
    args.outputs.debug  << { x: 16,      y: (16 + 90).from_top, w: 160, h: 90, r: 255, g: 255, b: 255 }.solid!
    args.outputs.debug  << { x: 16,      y: (16 + 90).from_top, w: 160, h: 90, path: :lights }
    args.outputs.debug  << { x: 16 + 80, y: (16 + 90 + 8).from_top, text: ":lights render_target", r: 255, g: 255, b: 255, size_enum: -3, alignment_enum: 1 }
  
    args.outputs.debug  << { x: 16 + 160 + 16,      y: (16 + 90).from_top, w: 160, h: 90, r: 255, g: 255, b: 255 }.solid!
    args.outputs.debug  << { x: 16 + 160 + 16,      y: (16 + 90).from_top, w: 160, h: 90, path: :scene }
    args.outputs.debug  << { x: 16 + 160 + 16 + 80, y: (16 + 90 + 8).from_top, text: ":scene render_target", r: 255, g: 255, b: 255, size_enum: -3, alignment_enum: 1 }
  end
  
  def tick args
    render args
    calc args
  end
  
  $gtk.reset

#+end_src

*** Advanced Rendering - Triangles - main.rb
#+begin_src ruby
  # ./samples/07_advanced_rendering/13_triangles/app/main.rb
  def tick args
    args.outputs.labels << {
      x: 640,
      y: 30.from_top,
      text: "Triangle rendering is available in Indie and Pro versions (ignored in Standard Edition).",
      alignment_enum: 1
    }
  
    dragonruby_logo_width  = 128
    dragonruby_logo_height = 101
  
    row_1 = 400
    row_2 = 250
  
    args.outputs.solids << make_triangle(
      640 - dragonruby_logo_width.half - dragonruby_logo_width,
      row_1,
      640 - dragonruby_logo_width,
      row_1 + 101,
      640 + dragonruby_logo_width.half - dragonruby_logo_width,
      row_1,
      0, 128, 128,
      128
    )
  
    args.outputs.solids << {
      x:  640 - dragonruby_logo_width.half,
      y:  row_1,
      x2: 640,
      y2: row_1 + dragonruby_logo_height,
      x3: 640 + dragonruby_logo_width.half,
      y3: row_1,
    }
  
    args.outputs.sprites << {
      x:  640 - dragonruby_logo_width.half + dragonruby_logo_width,
      y:  row_1,
      x2: 640 + dragonruby_logo_width,
      y2: row_1 + 101,
      x3: 640 + dragonruby_logo_width.half + dragonruby_logo_width,
      y3: row_1,
      path: 'dragonruby.png',
      source_x:  0,
      source_y:  0,
      source_x2: dragonruby_logo_width.half,
      source_y2: dragonruby_logo_height,
      source_x3: dragonruby_logo_width,
      source_y3: 0
    }
  
    args.outputs.primitives << make_triangle(
      640 - dragonruby_logo_width.half - dragonruby_logo_width,
      row_2,
      640 - dragonruby_logo_width,
      row_2 + 101,
      640 + dragonruby_logo_width.half - dragonruby_logo_width,
      row_2,
      0, 128, 128,
      args.state.tick_count.to_radians.sin_r.abs * 255
    )
  
    args.outputs.primitives << {
      x:  640 - dragonruby_logo_width.half,
      y:  row_2,
      x2: 640,
      y2: row_2 + dragonruby_logo_height,
      x3: 640 + dragonruby_logo_width.half,
      y3: row_2,
      r:  255
    }
  
    args.outputs.primitives << {
      x:  640 - dragonruby_logo_width.half + dragonruby_logo_width,
      y:  row_2,
      x2: 640 + dragonruby_logo_width,
      y2: row_2 + 101,
      x3: 640 + dragonruby_logo_width.half + dragonruby_logo_width,
      y3: row_2,
      path: 'dragonruby.png',
      source_x:  0,
      source_y:  0,
      source_x2: dragonruby_logo_width.half,
      source_y2: dragonruby_logo_height.half +
                 dragonruby_logo_height.half * Math.sin(args.state.tick_count.to_radians).abs,
      source_x3: dragonruby_logo_width,
      source_y3: 0
    }
  end
  
  def make_triangle *opts
    x, y, x2, y2, x3, y3, r, g, b, a = opts
    {
      x: x, y: y, x2: x2, y2: y2, x3: x3, y3: y3,
      r: r || 0,
      g: g || 0,
      b: b || 0,
      a: a || 255
    }
  end

#+end_src

*** Advanced Rendering - 14 Triangles Trapezoid - main.rb
#+begin_src ruby
  # ./samples/07_advanced_rendering/14_triangles_trapezoid/app/main.rb
  def tick args
    args.outputs.labels << {
      x: 640,
      y: 30.from_top,
      text: "Triangle rendering is available in Indie and Pro versions (ignored in Standard Edition).",
      alignment_enum: 1
    }
  
    transform_scale = ((args.state.tick_count / 3).sin.abs ** 5).half
    args.outputs.sprites << [
      { x:         600,
        y:         320,
        x2:        600,
        y2:        400,
        x3:        640,
        y3:        360,
        path:      "sprites/square/blue.png",
        source_x:  0,
        source_y:  0,
        source_x2: 0,
        source_y2: 80,
        source_x3: 40,
        source_y3: 40 },
      { x:         600,
        y:         400,
        x2:        680,
        y2:        (400 - 80 * transform_scale).round,
        x3:        640,
        y3:        360,
        path:      "sprites/square/blue.png",
        source_x:  0,
        source_y:  80,
        source_x2: 80,
        source_y2: 80,
        source_x3: 40,
        source_y3: 40 },
      { x:         640,
        y:         360,
        x2:        680,
        y2:        (400 - 80 * transform_scale).round,
        x3:        680,
        y3:        (320 + 80 * transform_scale).round,
        path:      "sprites/square/blue.png",
        source_x:  40,
        source_y:  40,
        source_x2: 80,
        source_y2: 80,
        source_x3: 80,
        source_y3: 0 },
      { x:         600,
        y:         320,
        x2:        640,
        y2:        360,
        x3:        680,
        y3:        (320 + 80 * transform_scale).round,
        path:      "sprites/square/blue.png",
        source_x:  0,
        source_y:  0,
        source_x2: 40,
        source_y2: 40,
        source_x3: 80,
        source_y3: 0 }
    ]
  end

#+end_src

*** Tweening Lerping Easing Functions - Easing Functions - main.rb
#+begin_src ruby
  # ./samples/08_tweening_lerping_easing_functions/01_easing_functions/app/main.rb
  def tick args
    # STOP! Watch the following presentation first!!!!
    # Math for Game Programmers: Fast and Funky 1D Nonlinear Transformations
    # https://www.youtube.com/watch?v=mr5xkf6zSzk
  
    # You've watched the talk, yes? YES???
  
    # define starting and ending points of properties to animate
    args.state.target_x = 1180
    args.state.target_y = 620
    args.state.target_w = 100
    args.state.target_h = 100
    args.state.starting_x = 0
    args.state.starting_y = 0
    args.state.starting_w = 300
    args.state.starting_h = 300
  
    # define start time and duration of animation
    args.state.start_animate_at = 3.seconds # this is the same as writing 60 * 5 (or 300)
    args.state.duration = 2.seconds # this is the same as writing 60 * 2 (or 120)
  
    # define type of animations
    # Here are all the options you have for values you can put in the array:
    # :identity, :quad, :cube, :quart, :quint, :flip
  
    # Linear is defined as:
    # [:identity]
    #
    # Smooth start variations are:
    # [:quad]
    # [:cube]
    # [:quart]
    # [:quint]
  
    # Linear reversed, and smooth stop are the same as the animations defined above, but reversed:
    # [:flip, :identity]
    # [:flip, :quad, :flip]
    # [:flip, :cube, :flip]
    # [:flip, :quart, :flip]
    # [:flip, :quint, :flip]
  
    # You can also do custom definitions. See the bottom of the file details
    # on how to do that. I've defined a couple for you:
    # [:smoothest_start]
    # [:smoothest_stop]
  
    # CHANGE THIS LINE TO ONE OF THE LINES ABOVE TO SEE VARIATIONS
    args.state.animation_type = [:identity]
    # args.state.animation_type = [:quad]
    # args.state.animation_type = [:cube]
    # args.state.animation_type = [:quart]
    # args.state.animation_type = [:quint]
    # args.state.animation_type = [:flip, :identity]
    # args.state.animation_type = [:flip, :quad, :flip]
    # args.state.animation_type = [:flip, :cube, :flip]
    # args.state.animation_type = [:flip, :quart, :flip]
    # args.state.animation_type = [:flip, :quint, :flip]
    # args.state.animation_type = [:smoothest_start]
    # args.state.animation_type = [:smoothest_stop]
  
    # THIS IS WHERE THE MAGIC HAPPENS!
    # Numeric#ease
    progress = args.state.start_animate_at.ease(args.state.duration, args.state.animation_type)
  
    # Numeric#ease needs to called:
    # 1. On the number that represents the point in time you want to start, and takes two parameters:
    #   a. The first parameter is how long the animation should take.
    #   b. The second parameter represents the functions that need to be called.
    #
    # For example, if I wanted an animate to start 3 seconds in, and last for 10 seconds,
    # and I want to animation to start fast and end slow, I would do:
    # (60 * 3).ease(60 * 10, :flip, :quint, :flip)
  
    #        initial value           delta to the final value
    calc_x = args.state.starting_x + (args.state.target_x - args.state.starting_x) * progress
    calc_y = args.state.starting_y + (args.state.target_y - args.state.starting_y) * progress
    calc_w = args.state.starting_w + (args.state.target_w - args.state.starting_w) * progress
    calc_h = args.state.starting_h + (args.state.target_h - args.state.starting_h) * progress
  
    args.outputs.solids << [calc_x, calc_y, calc_w, calc_h, 0, 0, 0]
  
    # count down
    count_down = args.state.start_animate_at - args.state.tick_count
    if count_down > 0
      args.outputs.labels << [640, 375, "Running: #{args.state.animation_type} in...", 3, 1]
      args.outputs.labels << [640, 345, "%.2f" % count_down.fdiv(60), 3, 1]
    elsif progress >= 1
      args.outputs.labels << [640, 360, "Click screen to reset.", 3, 1]
      if args.inputs.click
        $gtk.reset
      end
    end
  end
  
  # $gtk.reset
  
  # you can make own variations of animations using this
  module Easing
    # you have access to all the built in functions: identity, flip, quad, cube, quart, quint
    def self.smoothest_start x
      quad(quint(x))
    end
  
    def self.smoothest_stop x
      flip(quad(quint(flip(x))))
    end
  
    # this is the source for the existing easing functions
    def self.identity x
      x
    end
  
    def self.flip x
      1 - x
    end
  
    def self.quad x
      x * x
    end
  
    def self.cube x
      x * x * x
    end
  
    def self.quart x
      x * x * x * x * x
    end
  
    def self.quint x
      x * x * x * x * x * x
    end
  end

#+end_src

*** Tweening Lerping Easing Functions - Cubic Bezier - main.rb
#+begin_src ruby
  # ./samples/08_tweening_lerping_easing_functions/02_cubic_bezier/app/main.rb
  def tick args
    args.outputs.background_color = [33, 33, 33]
    args.outputs.lines << bezier(100, 100,
                                 100, 620,
                                 1180, 620,
                                 1180, 100,
                                 0)
  
    args.outputs.lines << bezier(100, 100,
                                 100, 620,
                                 1180, 620,
                                 1180, 100,
                                 20)
  end
  
  
  def bezier x1, y1, x2, y2, x3, y3, x4, y4, step
    step ||= 0
    color = [200, 200, 200]
    points = points_for_bezier [x1, y1], [x2, y2], [x3, y3], [x4, y4], step
  
    points.each_cons(2).map do |p1, p2|
      [p1, p2, color]
    end
  end
  
  def points_for_bezier p1, p2, p3, p4, step
    points = []
    if step == 0
      [p1, p2, p3, p4]
    else
      t_step = 1.fdiv(step + 1)
      t = 0
      t += t_step
      points = []
      while t < 1
        points << [
          b_for_t(p1.x, p2.x, p3.x, p4.x, t),
          b_for_t(p1.y, p2.y, p3.y, p4.y, t),
        ]
        t += t_step
      end
  
      [
        p1,
        *points,
        p4
      ]
    end
  end
  
  def b_for_t v0, v1, v2, v3, t
    pow(1 - t, 3) * v0 +
    3 * pow(1 - t, 2) * t * v1 +
    3 * (1 - t) * pow(t, 2) * v2 +
    pow(t, 3) * v3
  end
  
  def pow n, to
    n ** to
  end

#+end_src

*** Tweening Lerping Easing Functions - Easing Using Spline - main.rb
#+begin_src ruby
  # ./samples/08_tweening_lerping_easing_functions/03_easing_using_spline/app/main.rb
  def tick args
    args.state.duration = 10.seconds
    args.state.spline = [
      [0.0, 0.33, 0.66, 1.0],
      [1.0, 1.0,  1.0,  1.0],
      [1.0, 0.66, 0.33, 0.0],
    ]
  
    args.state.simulation_tick = args.state.tick_count % args.state.duration
    progress = 0.ease_spline_extended args.state.simulation_tick, args.state.duration, args.state.spline
    args.outputs.borders << args.grid.rect
    args.outputs.solids << [20 + 1240 * progress,
                            20 +  680 * progress,
                            20, 20].anchor_rect(0.5, 0.5)
    args.outputs.labels << [10,
                            710,
                            "perc: #{"%.2f" % (args.state.simulation_tick / args.state.duration)} t: #{args.state.simulation_tick}"]
  end

#+end_src

*** Tweening Lerping Easing Functions - Parametric Enemy Movement - main.rb
#+begin_src ruby
  # ./samples/08_tweening_lerping_easing_functions/04_parametric_enemy_movement/app/main.rb
  def new_star args
    { x: 1280.randomize(:ratio),
      starting_y: 800,
      distance_to_travel: 900 + 100.randomize(:ratio),
      duration: 100.randomize(:ratio) + 60,
      created_at: args.state.tick_count,
      max_alpha: 128.randomize(:ratio) + 128,
      b: 255.randomize(:ratio),
      g: 200.randomize(:ratio),
      w: 1.randomize(:ratio) + 1,
      h: 1.randomize(:ratio) + 1 }
  end
  
  def new_enemy args
    { x: 1280.randomize(:ratio),
      starting_y: 800,
      distance_to_travel: -900,
      duration: 60.randomize(:ratio) + 180,
      created_at: args.state.tick_count,
      w: 32,
      h: 32,
      fire_rate: (30.randomize(:ratio) + (60 - args.state.score)).to_i }
  end
  
  def new_bullet args, starting_x, starting_y, enemy_speed
    { x: starting_x,
      starting_y: starting_y,
      distance_to_travel: -900,
      created_at: args.state.tick_count,
      duration: 900 / (enemy_speed.abs + 2.0 + (5.0 * args.state.score.fdiv(100))).abs,
      w: 5,
      h: 5 }
  end
  
  def new_player_bullet args, starting_x, starting_y, player_speed
    { x: starting_x,
      starting_y: starting_y,
      distance_to_travel: 900,
      created_at: args.state.tick_count,
      duration: 900 / (player_speed + 2.0),
      w: 5,
      h: 5 }
  end
  
  def defaults args
    args.outputs.background_color  = [0, 0, 0]
    args.state.score             ||= 0
    args.state.stars             ||= []
    args.state.enemies           ||= []
    args.state.bullets           ||= []
    args.state.player_bullets    ||= []
    args.state.max_stars           = 50
    args.state.max_enemies         = 10
    args.state.player.x          ||= 640
    args.state.player.y          ||= 100
    args.state.player.w          ||= 32
    args.state.player.h          ||= 32
  
    if args.state.tick_count == 0
      args.state.stars.clear
      args.state.max_stars.times do
        s = new_star args
        s[:created_at] += s[:duration].randomize(:ratio)
        args.state.stars << s
      end
    end
  
    if args.state.tick_count == 0
      args.state.enemies.clear
      args.state.max_enemies.times do
        s = new_enemy args
        s[:created_at] += s[:duration].randomize(:ratio)
        args.state.enemies << s
      end
    end
  end
  
  def input args
    if args.inputs.keyboard.left
      args.state.player.x -= 5
    elsif args.inputs.keyboard.right
      args.state.player.x += 5
    end
  
    if args.inputs.keyboard.up
      args.state.player.y += 5
    elsif args.inputs.keyboard.down
      args.state.player.y -= 5
    end
  
    if args.inputs.keyboard.key_down.space
      args.state.player_bullets << new_player_bullet(args,
                                                     args.state.player.x + args.state.player.w.half,
                                                     args.state.player.y + args.state.player.h, 5)
    end
  
    args.state.player.y = args.state.player.y.greater(0).lesser(720 - args.state.player.w)
    args.state.player.x = args.state.player.x.greater(0).lesser(1280 - args.state.player.h)
  end
  
  def completed? entity
    (entity[:created_at] + entity[:duration]).elapsed_time > 0
  end
  
  def calc_stars args
    if (stars_to_add = args.state.max_stars - args.state.stars.length) > 0
      stars_to_add.times { args.state.stars << new_star(args) }
    end
    args.state.stars = args.state.stars.reject { |s| completed? s }
  end
  
  def move_enemies args
    if (enemies_to_add = args.state.max_enemies - args.state.enemies.length) > 0
      enemies_to_add.times { args.state.enemies << new_enemy(args) }
    end
  
    args.state.enemies = args.state.enemies.reject { |s| completed? s }
  end
  
  def move_bullets args
    args.state.enemies.each do |e|
      if args.state.tick_count.mod_zero?(e[:fire_rate])
        args.state.bullets << new_bullet(args, e[:x] + e[:w].half, current_y(e), e[:distance_to_travel] / e[:duration])
      end
    end
  
    args.state.bullets = args.state.bullets.reject { |s| completed? s }
    args.state.player_bullets = args.state.player_bullets.reject { |s| completed? s }
  end
  
  def intersect? entity_one, entity_two
    entity_one.merge(y: current_y(entity_one))
              .intersect_rect? entity_two.merge(y: current_y(entity_two))
  end
  
  def kill args
    bullets_hitting_enemies = []
    dead_bullets = []
    dead_enemies = []
  
    args.state.player_bullets.each do |b|
      args.state.enemies.each do |e|
        if intersect? b, e
          dead_bullets << b
          dead_enemies << e
        end
      end
    end
  
    args.state.score += dead_enemies.length
  
    args.state.player_bullets.reject! { |b| dead_bullets.include? b }
    args.state.enemies.reject! { |e| dead_enemies.include? e }
  
    dead = args.state.bullets.any? do |b|
      [args.state.player.x,
       args.state.player.y,
       args.state.player.w,
       args.state.player.h].intersect_rect? b.merge(y: current_y(b))
    end
    return unless dead
    args.gtk.reset
    defaults args
  end
  
  def calc args
    calc_stars args
    move_enemies args
    move_bullets args
    kill args
  end
  
  def current_y entity
    entity[:starting_y] + (entity[:distance_to_travel] * entity[:created_at].ease(entity[:duration], :identity))
  end
  
  def render args
    args.outputs.solids << args.state.stars.map do |s|
      [s[:x],
       current_y(s),
       s[:w], s[:h], 0, s[:g], s[:b], s[:max_alpha] * s[:created_at].ease(20, :identity)]
    end
  
    args.outputs.borders << args.state.enemies.map do |s|
      [s[:x],
       current_y(s),
       s[:w], s[:h], 255, 0, 0]
    end
  
    args.outputs.borders << args.state.bullets.map do |b|
      [b[:x],
       current_y(b),
       b[:w], b[:h], 255, 0, 0]
    end
  
    args.outputs.borders << args.state.player_bullets.map do |b|
      [b[:x],
       current_y(b),
       b[:w], b[:h], 255, 255, 255]
    end
  
    args.borders << [args.state.player.x,
                     args.state.player.y,
                     args.state.player.w,
                     args.state.player.h, 255, 255, 255]
  end
  
  def tick args
    defaults args
    input args
    calc args
    render args
  end

#+end_src

*** Performance - Sprites As Hash - main.rb
#+begin_src ruby
  # ./samples/09_performance/01_sprites_as_hash/app/main.rb
  
  # Sprites represented as Hashes using the queue ~args.outputs.sprites~
  # code up, but are the "slowest" to render.
  # The reason for this is the access of the key in the Hash and also
  # because the data args.outputs.sprites is cleared every tick.
  def random_x args
    (args.grid.w.randomize :ratio) * -1
  end
  
  def random_y args
    (args.grid.h.randomize :ratio) * -1
  end
  
  def random_speed
    1 + (4.randomize :ratio)
  end
  
  def new_star args
    {
      x: (random_x args),
      y: (random_y args),
      w: 4, h: 4, path: 'sprites/tiny-star.png',
      s: random_speed
    }
  end
  
  def move_star args, star
    star.x += star[:s]
    star.y += star[:s]
    if star.x > args.grid.w || star.y > args.grid.h
      star.x = (random_x args)
      star.y = (random_y args)
      star[:s] = random_speed
    end
  end
  
  def tick args
    args.state.star_count ||= 0
  
    # sets console command when sample app initially opens
    if Kernel.global_tick_count == 0
      puts ""
      puts ""
      puts "========================================================="
      puts "* INFO: Sprites, Hashes"
      puts "* INFO: Please specify the number of sprites to render."
      args.gtk.console.set_command "reset_with count: 100"
    end
  
    # init
    if args.state.tick_count == 0
      args.state.stars = args.state.star_count.map { |i| new_star args }
    end
  
    # update
    args.state.stars.each { |s| move_star args, s }
  
    # render
    args.outputs.sprites << args.state.stars
    args.outputs.background_color = [0, 0, 0]
    args.outputs.primitives << args.gtk.current_framerate_primitives
  end
  
  # resets game, and assigns star count given by user
  def reset_with count: count
    $gtk.reset
    $gtk.args.state.star_count = count
  end

#+end_src

*** Performance - Sprites As Entities - main.rb
#+begin_src ruby
  # ./samples/09_performance/02_sprites_as_entities/app/main.rb
  # Sprites represented as Entities using the queue ~args.outputs.sprites~
  # yields nicer access apis over Hashes, but require a bit more code upfront.
  # The hash sample has to use star[:s] to get the speed of the star, but
  # an entity can use .s instead.
  def random_x args
    (args.grid.w.randomize :ratio) * -1
  end
  
  def random_y args
    (args.grid.h.randomize :ratio) * -1
  end
  
  def random_speed
    1 + (4.randomize :ratio)
  end
  
  def new_star args
    args.state.new_entity :star, {
      x: (random_x args),
      y: (random_y args),
      w: 4, h: 4,
      path: 'sprites/tiny-star.png',
      s: random_speed
    }
  end
  
  def move_star args, star
    star.x += star.s
    star.y += star.s
    if star.x > args.grid.w || star.y > args.grid.h
      star.x = (random_x args)
      star.y = (random_y args)
      star.s = random_speed
    end
  end
  
  def tick args
    args.state.star_count ||= 0
  
    # sets console command when sample app initially opens
    if Kernel.global_tick_count == 0
      puts ""
      puts ""
      puts "========================================================="
      puts "* INFO: Sprites, Open Entities"
      puts "* INFO: Please specify the number of sprites to render."
      args.gtk.console.set_command "reset_with count: 100"
    end
  
    # init
    if args.state.tick_count == 0
      args.state.stars = args.state.star_count.map { |i| new_star args }
    end
  
    # update
    args.state.stars.each { |s| move_star args, s }
  
    # render
    args.outputs.sprites << args.state.stars
    args.outputs.background_color = [0, 0, 0]
    args.outputs.primitives << args.gtk.current_framerate_primitives
  end
  
  # resets game, and assigns star count given by user
  def reset_with count: count
    $gtk.reset
    $gtk.args.state.star_count = count
  end

#+end_src

*** Performance - Sprites As Struct - main.rb
#+begin_src ruby
  # ./samples/09_performance/03_sprites_as_struct/app/main.rb
  # create a Struct variant that allows for named parameters on construction.
  class NamedStruct < Struct
    def initialize **opts
      super(*members.map { |k| opts[k] })
    end
  end
  
  # create a Star NamedStruct
  Star = NamedStruct.new(:x, :y, :w, :h, :path, :s,
                         :angle, :angle_anchor_x, :angle_anchor_y,
                         :r, :g, :b, :a,
                         :tile_x, :tile_y,
                         :tile_w, :tile_h,
                         :source_x, :source_y,
                         :source_w, :source_h,
                         :flip_horizontally, :flip_vertically,
                         :blendmode_enum)
  
  # Sprites represented as Structs. They require a little bit more code than Hashes,
  # but are the a little faster to render too.
  def random_x args
    (args.grid.w.randomize :ratio) * -1
  end
  
  def random_y args
    (args.grid.h.randomize :ratio) * -1
  end
  
  def random_speed
    1 + (4.randomize :ratio)
  end
  
  def new_star args
    Star.new x: (random_x args),
             y: (random_y args),
             w: 4, h: 4,
             path: 'sprites/tiny-star.png',
             s: random_speed
  end
  
  def move_star args, star
    star.x += star[:s]
    star.y += star[:s]
    if star.x > args.grid.w || star.y > args.grid.h
      star.x = (random_x args)
      star.y = (random_y args)
      star[:s] = random_speed
    end
  end
  
  def tick args
    args.state.star_count ||= 0
  
    # sets console command when sample app initially opens
    if Kernel.global_tick_count == 0
      puts ""
      puts ""
      puts "========================================================="
      puts "* INFO: Sprites, Structs"
      puts "* INFO: Please specify the number of sprites to render."
      args.gtk.console.set_command "reset_with count: 100"
    end
  
    # init
    if args.state.tick_count == 0
      args.state.stars = args.state.star_count.map { |i| new_star args }
    end
  
    # update
    args.state.stars.each { |s| move_star args, s }
  
    # render
    args.outputs.sprites << args.state.stars
    args.outputs.background_color = [0, 0, 0]
    args.outputs.primitives << args.gtk.current_framerate_primitives
  end
  
  # resets game, and assigns star count given by user
  def reset_with count: count
    $gtk.reset
    $gtk.args.state.star_count = count
  end

#+end_src

*** Performance - Sprites As Strict Entities - main.rb
#+begin_src ruby
  # ./samples/09_performance/04_sprites_as_strict_entities/app/main.rb
  # Sprites represented as StrictEntities using the queue ~args.outputs.sprites~
  # yields apis access similar to Entities, but all properties that can be set on the
  # entity must be predefined with a default value. Strict entities do not support the
  # addition of new properties after the fact. They are more performant than OpenEntities
  # because of this constraint.
  def random_x args
    (args.grid.w.randomize :ratio) * -1
  end
  
  def random_y args
    (args.grid.h.randomize :ratio) * -1
  end
  
  def random_speed
    1 + (4.randomize :ratio)
  end
  
  def new_star args
    args.state.new_entity_strict(:star,
                                 x: (random_x args),
                                 y: (random_y args),
                                 w: 4, h: 4,
                                 path: 'sprites/tiny-star.png',
                                 s: random_speed) do |entity|
      # invoke attr_sprite so that it responds to
      # all properties that are required to render a sprite
      entity.attr_sprite
    end
  end
  
  def move_star args, star
    star.x += star.s
    star.y += star.s
    if star.x > args.grid.w || star.y > args.grid.h
      star.x = (random_x args)
      star.y = (random_y args)
      star.s = random_speed
    end
  end
  
  def tick args
    args.state.star_count ||= 0
  
    # sets console command when sample app initially opens
    if Kernel.global_tick_count == 0
      puts ""
      puts ""
      puts "========================================================="
      puts "* INFO: Sprites, Strict Entities"
      puts "* INFO: Please specify the number of sprites to render."
      args.gtk.console.set_command "reset_with count: 100"
    end
  
    # init
    if args.state.tick_count == 0
      args.state.stars = args.state.star_count.map { |i| new_star args }
    end
  
    # update
    args.state.stars.each { |s| move_star args, s }
  
    # render
    args.outputs.sprites << args.state.stars
    args.outputs.background_color = [0, 0, 0]
    args.outputs.primitives << args.gtk.current_framerate_primitives
  end
  
  # resets game, and assigns star count given by user
  def reset_with count: count
    $gtk.reset
    $gtk.args.state.star_count = count
  end

#+end_src

*** Performance - Sprites As Classes - main.rb
#+begin_src ruby
  # ./samples/09_performance/05_sprites_as_classes/app/main.rb
  # Sprites represented as Classes using the queue ~args.outputs.sprites~.
  # gives you full control of property declaration and method invocation.
  # They are more performant than OpenEntities and StrictEntities, but more code upfront.
  class Star
    attr_sprite
  
    def initialize grid
      @grid = grid
      @x = (rand @grid.w) * -1
      @y = (rand @grid.h) * -1
      @w    = 4
      @h    = 4
      @s    = 1 + (4.randomize :ratio)
      @path = 'sprites/tiny-star.png'
    end
  
    def move
      @x += @s
      @y += @s
      @x = (rand @grid.w) * -1 if @x > @grid.right
      @y = (rand @grid.h) * -1 if @y > @grid.top
    end
  end
  
  # calls methods needed for game to run properly
  def tick args
    # sets console command when sample app initially opens
    if Kernel.global_tick_count == 0
      puts ""
      puts ""
      puts "========================================================="
      puts "* INFO: Sprites, Classes"
      puts "* INFO: Please specify the number of sprites to render."
      args.gtk.console.set_command "reset_with count: 100"
    end
  
    # init
    if args.state.tick_count == 0
      args.state.stars = args.state.star_count.map { |i| Star.new args.grid }
    end
  
    # update
    args.state.stars.each(&:move)
  
    # render
    args.outputs.sprites << args.state.stars
    args.outputs.background_color = [0, 0, 0]
    args.outputs.primitives << args.gtk.current_framerate_primitives
  end
  
  # resets game, and assigns star count given by user
  def reset_with count: count
    $gtk.reset
    $gtk.args.state.star_count = count
  end

#+end_src

*** Performance - Static Sprites As Classes - main.rb
#+begin_src ruby
  # ./samples/09_performance/06_static_sprites_as_classes/app/main.rb
  # Sprites represented as Classes using the queue ~args.outputs.static_sprites~.
  # bypasses the queue behavior of ~args.outputs.sprites~. All instances are held
  # by reference. You get better performance, but you are mutating state of held objects
  # which is less functional/data oriented.
  class Star
    attr_sprite
  
    def initialize grid
      @grid = grid
      @x = (rand @grid.w) * -1
      @y = (rand @grid.h) * -1
      @w    = 4
      @h    = 4
      @s    = 1 + (4.randomize :ratio)
      @path = 'sprites/tiny-star.png'
    end
  
    def move
      @x += @s
      @y += @s
      @x = (rand @grid.w) * -1 if @x > @grid.right
      @y = (rand @grid.h) * -1 if @y > @grid.top
    end
  end
  
  # calls methods needed for game to run properly
  def tick args
    # sets console command when sample app initially opens
    if Kernel.global_tick_count == 0
      puts ""
      puts ""
      puts "========================================================="
      puts "* INFO: Static Sprites, Classes"
      puts "* INFO: Please specify the number of sprites to render."
      args.gtk.console.set_command "reset_with count: 100"
    end
  
    # init
    if args.state.tick_count == 0
      args.state.stars = args.state.star_count.map { |i| Star.new args.grid }
      args.outputs.static_sprites << args.state.stars
    end
  
    # update
    args.state.stars.each(&:move)
  
    # render
    args.outputs.background_color = [0, 0, 0]
    args.outputs.primitives << args.gtk.current_framerate_primitives
  end
  
  # resets game, and assigns star count given by user
  def reset_with count: count
    $gtk.reset
    $gtk.args.state.star_count = count
  end

#+end_src

*** Performance - Static Sprites As Classes With Custom Drawing - main.rb
#+begin_src ruby
  # ./samples/09_performance/07_static_sprites_as_classes_with_custom_drawing/app/main.rb
  # Sprites represented as Classes, with a draw_override method, and using the queue ~args.outputs.static_sprites~.
  # is the fastest approach. This is comparable to what other game engines set as the default behavior.
  # There are tradeoffs for all this speed if the creation of a full blown class, and bypassing
  # functional/data-oriented practices.
  class Star
    def initialize grid
      @grid = grid
      @x = (rand @grid.w) * -1
      @y = (rand @grid.h) * -1
      @w    = 4
      @h    = 4
      @s    = 1 + (4.randomize :ratio)
      @path = 'sprites/tiny-star.png'
    end
  
    def move
      @x += @s
      @y += @s
      @x = (rand @grid.w) * -1 if @x > @grid.right
      @y = (rand @grid.h) * -1 if @y > @grid.top
    end
  
    # if the object that is in args.outputs.sprites (or static_sprites)
    # respond_to? :draw_override, then the method is invoked giving you
    # access to the class used to draw to the canvas.
    def draw_override ffi_draw
      # first move then draw
      move
  
      # The argument order for ffi.draw_sprite is:
      # x, y, w, h, path
      ffi_draw.draw_sprite @x, @y, @w, @h, @path
  
      # The argument order for ffi_draw.draw_sprite_2 is (pass in nil for default value):
      # x, y, w, h, path,
      # angle, alpha
  
      # The argument order for ffi_draw.draw_sprite_3 is:
      # x, y, w, h,
      # path,
      # angle,
      # alpha, red_saturation, green_saturation, blue_saturation
      # tile_x, tile_y, tile_w, tile_h,
      # flip_horizontally, flip_vertically,
      # angle_anchor_x, angle_anchor_y,
      # source_x, source_y, source_w, source_h
  
      # The argument order for ffi_draw.draw_sprite_4 is:
      # x, y, w, h,
      # path,
      # angle,
      # alpha, red_saturation, green_saturation, blue_saturation
      # tile_x, tile_y, tile_w, tile_h,
      # flip_horizontally, flip_vertically,
      # angle_anchor_x, angle_anchor_y,
      # source_x, source_y, source_w, source_h,
      # blendmode_enum
    end
  end
  
  # calls methods needed for game to run properly
  def tick args
    # sets console command when sample app initially opens
    if Kernel.global_tick_count == 0
      puts ""
      puts ""
      puts "========================================================="
      puts "* INFO: Static Sprites, Classes, Draw Override"
      puts "* INFO: Please specify the number of sprites to render."
      args.gtk.console.set_command "reset_with count: 100"
    end
  
    # init
    if args.state.tick_count == 0
      args.state.stars = args.state.star_count.map { |i| Star.new args.grid }
      args.outputs.static_sprites << args.state.stars
    end
  
    # render framerate
    args.outputs.background_color = [0, 0, 0]
    args.outputs.primitives << args.gtk.current_framerate_primitives
  end
  
  # resets game, and assigns star count given by user
  def reset_with count: count
    $gtk.reset
    $gtk.args.state.star_count = count
  end

#+end_src

*** Performance - Collision Limits - main.rb
#+begin_src ruby
  # ./samples/09_performance/08_collision_limits/app/main.rb
  =begin
  
   Reminders:
   - find_all: Finds all elements of a collection that meet certain requirements.
     In this sample app, we're finding all bodies that intersect with the center body.
  
   - args.outputs.solids: An array. The values generate a solid.
     The parameters are [X, Y, WIDTH, HEIGHT, RED, GREEN, BLUE]
     For more information about solids, go to mygame/documentation/03-solids-and-borders.md.
  
   - args.outputs.labels: An array. The values generate a label.
     The parameters are [X, Y, TEXT, SIZE, ALIGNMENT, RED, GREEN, BLUE, ALPHA, FONT STYLE]
     For more information about labels, go to mygame/documentation/02-labels.md.
  
   - ARRAY#intersect_rect?: Returns true or false depending on if two rectangles intersect.
  
  =end
  
  # This code demonstrates moving objects that loop around once they exceed the scope of the screen,
  # which has dimensions of 1280 by 720, and also detects collisions between objects called "bodies".
  
  def body_count num
    $gtk.args.state.other_bodies = num.map { [1280 * rand, 720 * rand, 10, 10] } # other_bodies set using num collection
  end
  
  def tick args
  
    # Center body's values are set using an array
    # Map is used to set values of 2000 other bodies
    # All bodies that intersect with center body are stored in collisions collection
    args.state.center_body  ||= [640 - 100, 360 - 100, 200, 200] # calculations done to place body in center
    args.state.other_bodies ||= 2000.map { [1280 * rand, 720 * rand, 10, 10] } # 2000 bodies given random position on screen
  
    # finds all bodies that intersect with center body, stores them in collisions
    collisions = args.state.other_bodies.find_all { |b| b.intersect_rect? args.state.center_body }
  
    args.borders << args.state.center_body # outputs center body as a black border
  
    # transparency changes based on number of collisions; the more collisions, the redder (more transparent) the box becomes
    args.solids  << [args.state.center_body, 255, 0, 0, collisions.length * 5] # center body is red solid
    args.solids  << args.state.other_bodies # other bodies are output as (black) solids, as well
  
    args.labels  << [10, 30, args.gtk.current_framerate] # outputs frame rate in bottom left corner
  
    # Bodies are returned to bottom left corner if positions exceed scope of screen
    args.state.other_bodies.each do |b| # for each body in the other_bodies collection
      b.x += 5 # x and y are both incremented by 5
      b.y += 5
      b.x = 0 if b.x > 1280 # x becomes 0 if star exceeds scope of screen (goes too far right)
      b.y = 0 if b.y > 720 # y becomes 0 if star exceeds scope of screen (goes too far up)
    end
  end
  
  # Resets the game.
  $gtk.reset

#+end_src

*** Performance - Collision Limits Many To Many - main.rb
#+begin_src ruby
  # ./samples/09_performance/09_collision_limits_many_to_many/app/main.rb
  class Square
    attr :x, :y, :w, :h
  
    def initialize grid
      @grid = grid
      @x = (rand @grid.w)
      @y = (rand @grid.h)
      @w    = 20
      @h    = 20
      @s    = 1 + (4.randomize :ratio)
      @path = 'sprites/square/blue.png'
    end
  
    def mark_collisions all
      # be sure to do an optimized compilation -O3
  
      # using FFI function
  
      if all[self]
        @path = 'sprites/square/red.png'
      else
        @path = 'sprites/square/blue.png'
      end
    end
  
    def draw_override ffi_draw
      ffi_draw.draw_sprite @x, @y, @w, @h, @path
    end
  end
  
  class Game
    attr_gtk
  
    def tick
      if Kernel.global_tick_count == 0
        puts ""
        puts ""
        puts "========================================================="
        puts "* INFO: Many to Many Collisions"
        puts "* INFO: Please specify the number of sprites to check collisions on."
        args.gtk.console.set_command "reset_with count: 100"
      end
  
      if args.state.tick_count == 0
        args.state.stars = args.state.star_count.map { |i| Square.new args.grid }
        args.outputs.static_sprites << args.state.stars
      end
  
      state.all_collisions = GTK::Geometry.find_collisions args.state.stars
      Fn.each_send args.state.stars, self, :mark_collision
  
      args.outputs.background_color = [0, 0, 0]
      args.outputs.primitives << args.gtk.current_framerate_primitives
    end
  
    def mark_collision star
      star.mark_collisions state.all_collisions
    end
  
    def reset_with count: count
      $gtk.reset
      $gtk.args.state.star_count = count
    end
  end
  
  def tick args
    $game ||= Game.new
    $game.args = args and $game.tick
  end
  
  def reset_with count: count
    $game.reset_with count: count
  end

#+end_src

*** Advanced Debugging - Logging - main.rb
#+begin_src ruby
  # ./samples/10_advanced_debugging/00_logging/app/main.rb
  def tick args
    args.outputs.background_color = [255, 255, 255, 0]
    if args.state.tick_count == 0
      args.gtk.log_spam "log level spam"
      args.gtk.log_debug "log level debug"
      args.gtk.log_info "log level info"
      args.gtk.log_warn "log level warn"
      args.gtk.log_error "log level error"
      args.gtk.log_unfiltered "log level unfiltered"
      puts "This is a puts call"
      args.gtk.console.show
    end
  
    if args.state.tick_count == 60
      puts "This is a puts call on tick 60"
    elsif args.state.tick_count == 120
      puts "This is a puts call on tick 120"
    end
  end

#+end_src

*** Advanced Debugging - Trace Debugging - main.rb
#+begin_src ruby
  # ./samples/10_advanced_debugging/01_trace_debugging/app/main.rb
  class Game
    attr_gtk
  
    def method1 num
      method2 num
    end
  
    def method2 num
      method3 num
    end
  
    def method3 num
      method4 num
    end
  
    def method4 num
      if num == 1
        puts "UNLUCKY #{num}."
        state.unlucky_count += 1
        if state.unlucky_count > 3
          raise "NAT 1 finally occurred. Check app/trace.txt for all method invocation history."
        end
      else
        puts "LUCKY #{num}."
      end
    end
  
    def tick
      state.roll_history ||= []
      state.roll_history << rand(20) + 1
      state.countdown ||= 600
      state.countdown  -= 1
      state.unlucky_count ||= 0
      outputs.labels << [640, 360, "A dice roll of 1 will cause an exception.", 0, 1]
      if state.countdown > 0
        outputs.labels << [640, 340, "Dice roll countdown: #{state.countdown}", 0, 1]
      else
        state.attempts ||= 0
        state.attempts  += 1
        outputs.labels << [640, 340, "ROLLING! #{state.attempts}", 0, 1]
      end
      return if state.countdown > 0
      method1 state.roll_history[-1]
    end
  end
  
  $game = Game.new
  
  def tick args
    trace! $game # <------------------- TRACING ENABLED FOR THIS OBJECT
    $game.args = args
    $game.tick
  end

#+end_src

*** Advanced Debugging - Trace Debugging Classes - main.rb
#+begin_src ruby
  # ./samples/10_advanced_debugging/02_trace_debugging_classes/app/main.rb
  class Foobar
    def initialize
      trace! # Trace is added to the constructor.
    end
  
    def clicky args
      return unless args.inputs.mouse.click
      try_rand rand
    end
  
    def try_rand num
      return if num < 0.9
      raise "Exception finally occurred. Take a look at logs/trace.txt #{num}."
    end
  end
  
  def tick args
    args.labels << [640, 360, "Start clicking. Eventually an exception will be thrown. Then look at logs/trace.txt.", 0, 1]
    args.state.foobar = Foobar.new if args.tick_count
    return unless args.state.foobar
    args.state.foobar.clicky args
  end

#+end_src

*** Advanced Debugging - Unit Tests - benchmark_api_tests.rb
#+begin_src ruby
  # ./samples/10_advanced_debugging/03_unit_tests/benchmark_api_tests.rb
  def test_benchmark_api args, assert
    result = args.gtk.benchmark iterations: 100,
                                only_one: -> () {
                                  r = 0
                                  (1..100).each do |i|
                                    r += 1
                                  end
                                }
  
    assert.equal! result.first_place.name, :only_one
  
    result = args.gtk.benchmark iterations: 100,
                                iterations_100: -> () {
                                  r = 0
                                  (1..100).each do |i|
                                    r += 1
                                  end
                                },
                                iterations_50: -> () {
                                  r = 0
                                  (1..50).each do |i|
                                    r += 1
                                  end
                                }
  
    assert.equal! result.first_place.name, :iterations_50
  
    result = args.gtk.benchmark iterations: 1,
                                iterations_100: -> () {
                                  r = 0
                                  (1..100).each do |i|
                                    r += 1
                                  end
                                },
                                iterations_50: -> () {
                                  r = 0
                                  (1..50).each do |i|
                                    r += 1
                                  end
                                }
  
    assert.equal! result.too_small_to_measure, true
  end

#+end_src

*** Advanced Debugging - Unit Tests - exception_raising_tests.rb
#+begin_src ruby
  # ./samples/10_advanced_debugging/03_unit_tests/exception_raising_tests.rb
  begin :shared
    class ExceptionalClass
      def initialize exception_to_throw = nil
        raise exception_to_throw if exception_to_throw
      end
    end
  end
  
  def test_exception_in_newing_object args, assert
    begin
      ExceptionalClass.new TypeError
      raise "Exception wasn't thrown!"
    rescue Exception => e
      assert.equal! e.class, TypeError, "Exceptions within constructor should be retained."
    end
  end
  
  $gtk.reset 100
  $gtk.log_level = :off

#+end_src

*** Advanced Debugging - Unit Tests - fn_tests.rb
#+begin_src ruby
  # ./samples/10_advanced_debugging/03_unit_tests/fn_tests.rb
  def infinity
    1 / 0
  end
  
  def neg_infinity
    -1 / 0
  end
  
  def nan
    0.0 / 0
  end
  
  def test_add args, assert
    assert.equal! (args.fn.add), 0
    assert.equal! (args.fn.+), 0
    assert.equal! (args.fn.+ 1, 2, 3), 6
    assert.equal! (args.fn.+ 0), 0
    assert.equal! (args.fn.+ 0, nil), 0
    assert.equal! (args.fn.+ 0, nan), nil
    assert.equal! (args.fn.+ 0, nil, infinity), nil
    assert.equal! (args.fn.+ [1, 2, 3, [4, 5, 6]]), 21
    assert.equal! (args.fn.+ [nil, [4, 5, 6]]), 15
  end
  
  def test_sub args, assert
    neg_infinity = infinity * -1
    assert.equal! (args.fn.+), 0
    assert.equal! (args.fn.- 1, 2, 3), -4
    assert.equal! (args.fn.- 4), -4
    assert.equal! (args.fn.- 4, nan), nil
    assert.equal! (args.fn.- 0, nil), 0
    assert.equal! (args.fn.- 0, nil, infinity), nil
    assert.equal! (args.fn.- [0, 1, 2, 3, [4, 5, 6]]), -21
    assert.equal! (args.fn.- [nil, 0, [4, 5, 6]]), -15
  end
  
  def test_div args, assert
    assert.equal! (args.fn.div), 1
    assert.equal! (args.fn./), 1
    assert.equal! (args.fn./ 6, 3), 2
    assert.equal! (args.fn./ 6, infinity), nil
    assert.equal! (args.fn./ 6, nan), nil
    assert.equal! (args.fn./ infinity), nil
    assert.equal! (args.fn./ 0), nil
    assert.equal! (args.fn./ 6, [3]), 2
  end
  
  def test_idiv args, assert
    assert.equal! (args.fn.idiv), 1
    assert.equal! (args.fn.idiv 7, 3), 2
    assert.equal! (args.fn.idiv 6, infinity), nil
    assert.equal! (args.fn.idiv 6, nan), nil
    assert.equal! (args.fn.idiv infinity), nil
    assert.equal! (args.fn.idiv 0), nil
    assert.equal! (args.fn.idiv 7, [3]), 2
  end
  
  def test_mul args, assert
    assert.equal! (args.fn.mul), 1
    assert.equal! (args.fn.*), 1
    assert.equal! (args.fn.* 7, 3), 21
    assert.equal! (args.fn.* 6, nan), nil
    assert.equal! (args.fn.* 6, infinity), nil
    assert.equal! (args.fn.* infinity), nil
    assert.equal! (args.fn.* 0), 0
    assert.equal! (args.fn.* 7, [3]), 21
  end
  
  def test_lt args, assert
    assert.equal! (args.fn.lt 1), 1
    assert.equal! (args.fn.lt), nil
    assert.equal! (args.fn.lt infinity), nil
    assert.equal! (args.fn.lt nan), nil
    assert.equal! (args.fn.lt 10, 9, 8), 8
    assert.equal! (args.fn.< 10, 9, 8), 8
    assert.equal! (args.fn.< [10, 9, [8]]), 8
    assert.equal! (args.fn.< 10, 10), nil
  end
  
  def test_lte args, assert
    assert.equal! (args.fn.lte 1), 1
    assert.equal! (args.fn.lte), nil
    assert.equal! (args.fn.lte infinity), nil
    assert.equal! (args.fn.lte nan), nil
    assert.equal! (args.fn.lte 10, 9, 8), 8
    assert.equal! (args.fn.lte 10, 10), 10
    assert.equal! (args.fn.lte  10, 9, [8]), 8
    assert.equal! (args.fn.<=  10, 9, 8), 8
  end
  
  def test_gt args, assert
    assert.equal! (args.fn.gt 1), 1
    assert.equal! (args.fn.gt), nil
    assert.equal! (args.fn.gt infinity), nil
    assert.equal! (args.fn.gt nan), nil
    assert.equal! (args.fn.gt 8, 9, 10), 10
    assert.equal! (args.fn.gt [8, 9, [10]]), 10
    assert.equal! (args.fn.gt 10, 10), nil
    assert.equal! (args.fn.gt 10, 10), nil
    assert.equal! (args.fn.gt 10, 9), nil
    assert.equal! (args.fn.>  8, 9, 10), 10
  end
  
  def test_gte args, assert
    assert.equal! (args.fn.gte 1), 1
    assert.equal! (args.fn.gte), nil
    assert.equal! (args.fn.gte infinity), nil
    assert.equal! (args.fn.gte nan), nil
    assert.equal! (args.fn.gte 8, 9, 10), 10
    assert.equal! (args.fn.gte 10, 10), 10
    assert.equal! (args.fn.gte 8, 9, [10]), 10
    assert.equal! (args.fn.gte 10, 9), nil
    assert.equal! (args.fn.>=  8, 9, 10), 10
  end
  
  
  def test_acopy args, assert
    orig  = [1, 2, 3]
    clone = args.fn.acopy orig
    assert.equal! clone, [1, 2, 3]
    assert.equal! clone, orig
    assert.not_equal! clone.object_id, orig.object_id
  end
  
  def test_aget args, assert
    assert.equal! (args.fn.aget [:a, :b, :c], 1), :b
    assert.equal! (args.fn.aget [:a, :b, :c], nil), nil
    assert.equal! (args.fn.aget nil, 1), nil
  end
  
  def test_alength args, assert
    assert.equal! (args.fn.alength [:a, :b, :c]), 3
    assert.equal! (args.fn.alength nil), nil
  end
  
  def test_amap args, assert
    inc = lambda { |i| i + 1 }
    ary = [1, 2, 3]
    assert.equal! (args.fn.amap ary, inc), [2, 3, 4]
    assert.equal! (args.fn.amap nil, inc), nil
    assert.equal! (args.fn.amap ary, nil), nil
    assert.equal! (args.fn.amap ary, inc).class, Array
  end
  
  def test_and args, assert
    assert.equal! (args.fn.and 1, 2, 3, 4), 4
    assert.equal! (args.fn.and 1, 2, nil, 4), nil
    assert.equal! (args.fn.and), true
  end
  
  def test_or args, assert
    assert.equal! (args.fn.or 1, 2, 3, 4), 1
    assert.equal! (args.fn.or 1, 2, nil, 4), 1
    assert.equal! (args.fn.or), nil
    assert.equal! (args.fn.or nil, nil, false, 5, 10), 5
  end
  
  def test_eq_eq args, assert
    assert.equal! (args.fn.eq?), true
    assert.equal! (args.fn.eq? 1, 0), false
    assert.equal! (args.fn.eq? 1, 1, 1), true
    assert.equal! (args.fn.== 1, 1, 1), true
    assert.equal! (args.fn.== nil, nil), true
  end
  
  def test_apply args, assert
    assert.equal! (args.fn.and [nil, nil, nil]), [nil, nil, nil]
    assert.equal! (args.fn.apply [nil, nil, nil], args.fn.method(:and)), nil
    and_lambda = lambda {|*xs| args.fn.and(*xs)}
    assert.equal! (args.fn.apply [nil, nil, nil], and_lambda), nil
  end
  
  def test_areduce args, assert
    assert.equal! (args.fn.areduce [1, 2, 3], 0, lambda { |i, a| i + a }), 6
  end
  
  def test_array_hash args, assert
    assert.equal! (args.fn.array_hash :a, 1, :b, 2), { a: 1, b: 2 }
    assert.equal! (args.fn.array_hash), { }
  end

#+end_src

*** Advanced Debugging - Unit Tests - gen_docs.rb
#+begin_src ruby
  # ./samples/10_advanced_debugging/03_unit_tests/gen_docs.rb
  # ./dragonruby mygame --eval samples/99_zz_gtk_unit_tests/gen_docs.rb --no-tick
  Kernel.export_docs!

#+end_src

*** Advanced Debugging - Unit Tests - geometry_tests.rb
#+begin_src ruby
  # ./samples/10_advanced_debugging/03_unit_tests/geometry_tests.rb
  begin :shared
    def primitive_representations x, y, w, h
      [
        [x, y, w, h],
        { x: x, y: y, w: w, h: h },
        RectForTest.new(x, y, w, h)
      ]
    end
  
    class RectForTest
      attr_sprite
  
      def initialize x, y, w, h
        @x = x
        @y = y
        @w = w
        @h = h
      end
  
      def to_s
        "RectForTest: #{[x, y, w, h]}"
      end
    end
  end
  
  begin :intersect_rect?
    def test_intersect_rect_point args, assert
      assert.true! [16, 13].intersect_rect?([13, 12, 4, 4]), "point intersects with rect."
    end
  
    def test_intersect_rect args, assert
      intersecting = primitive_representations(0, 0, 100, 100) +
                     primitive_representations(20, 20, 20, 20)
  
      intersecting.product(intersecting).each do |rect_one, rect_two|
        assert.true! rect_one.intersect_rect?(rect_two),
                     "intersect_rect? assertion failed for #{rect_one}, #{rect_two} (expected true)."
      end
  
      not_intersecting = [
        [ 0, 0, 5, 5],
        { x: 10, y: 10, w: 5, h: 5 },
        RectForTest.new(20, 20, 5, 5)
      ]
  
      not_intersecting.product(not_intersecting)
        .reject { |rect_one, rect_two| rect_one == rect_two }
        .each do |rect_one, rect_two|
        assert.false! rect_one.intersect_rect?(rect_two),
                      "intersect_rect? assertion failed for #{rect_one}, #{rect_two} (expected false)."
      end
    end
  end
  
  begin :inside_rect?
    def assert_inside_rect outer: nil, inner: nil, expected: nil, assert: nil
      assert.true! inner.inside_rect?(outer) == expected,
                   "inside_rect? assertion failed for outer: #{outer} inner: #{inner} (expected #{expected})."
    end
  
    def test_inside_rect args, assert
      outer_rects = primitive_representations(0, 0, 10, 10)
      inner_rects = primitive_representations(1, 1, 5, 5)
      primitive_representations(0, 0, 10, 10).product(primitive_representations(1, 1, 5, 5))
        .each do |outer, inner|
        assert_inside_rect outer: outer, inner: inner,
                           expected: true, assert: assert
      end
    end
  end
  
  begin :angle_to
    def test_angle_to args, assert
      origins = primitive_representations(0, 0, 0, 0)
      rights = primitive_representations(1, 0, 0, 0)
      aboves = primitive_representations(0, 1, 0, 0)
  
      origins.product(aboves).each do |origin, above|
        assert.equal! origin.angle_to(above), 90,
                      "A point directly above should be 90 degrees."
  
        assert.equal! above.angle_from(origin), 90,
                      "A point coming from above should be 90 degrees."
      end
  
      origins.product(rights).each do |origin, right|
        assert.equal! origin.angle_to(right) % 360, 0,
                      "A point directly to the right should be 0 degrees."
  
        assert.equal! right.angle_from(origin) % 360, 0,
                      "A point coming from the right should be 0 degrees."
  
      end
    end
  end
  
  begin :scale_rect
    def test_scale_rect args, assert
      assert.equal! [0, 0, 100, 100].scale_rect(0.5, 0.5),
                    [25.0, 25.0, 50.0, 50.0]
  
      assert.equal! [0, 0, 100, 100].scale_rect(0.5),
                    [0.0, 0.0, 50.0, 50.0]
  
      assert.equal! [0, 0, 100, 100].scale_rect_extended(percentage_x: 0.5, percentage_y: 0.5, anchor_x: 0.5, anchor_y: 0.5),
                    [25.0, 25.0, 50.0, 50.0]
  
      assert.equal! [0, 0, 100, 100].scale_rect_extended(percentage_x: 0.5, percentage_y: 0.5, anchor_x: 0, anchor_y: 0),
                    [0.0, 0.0, 50.0, 50.0]
    end
  end
  
  $gtk.reset 100
  $gtk.log_level = :off

#+end_src

*** Advanced Debugging - Unit Tests - http_tests.rb
#+begin_src ruby
  # ./samples/10_advanced_debugging/03_unit_tests/http_tests.rb
  def try_assert_or_schedule args, assert
    if $result[:complete]
      log_info "Request completed! Verifying."
      if $result[:http_response_code] != 200
        log_info "The request yielded a result of #{$result[:http_response_code]} instead of 200."
        exit
      end
      log_info ":try_assert_or_schedule succeeded!"
    else
      args.gtk.schedule_callback Kernel.tick_count + 10 do
        try_assert_or_schedule args, assert
      end
    end
  end
  
  def test_http args, assert
    $result = $gtk.http_get 'http://dragonruby.org'
    try_assert_or_schedule args, assert
  end
  
  $gtk.reset 100
  $gtk.log_level = :off

#+end_src

*** Advanced Debugging - Unit Tests - nil_coercion_tests.rb
#+begin_src ruby
  # ./samples/10_advanced_debugging/03_unit_tests/nil_coercion_tests.rb
  # numbers
  def test_open_entity_add_number args, assert
    assert.nil! args.state.i_value
    args.state.i_value += 5
    assert.equal! args.state.i_value, 5
  
    assert.nil! args.state.f_value
    args.state.f_value += 5.5
    assert.equal! args.state.f_value, 5.5
  end
  
  def test_open_entity_subtract_number args, assert
    assert.nil! args.state.i_value
    args.state.i_value -= 5
    assert.equal! args.state.i_value, -5
  
    assert.nil! args.state.f_value
    args.state.f_value -= 5.5
    assert.equal! args.state.f_value, -5.5
  end
  
  def test_open_entity_multiply_number args, assert
    assert.nil! args.state.i_value
    args.state.i_value *= 5
    assert.equal! args.state.i_value, 0
  
    assert.nil! args.state.f_value
    args.state.f_value *= 5.5
    assert.equal! args.state.f_value, 0
  end
  
  def test_open_entity_divide_number args, assert
    assert.nil! args.state.i_value
    args.state.i_value /= 5
    assert.equal! args.state.i_value, 0
  
    assert.nil! args.state.f_value
    args.state.f_value /= 5.5
    assert.equal! args.state.f_value, 0
  end
  
  # array
  def test_open_entity_add_array args, assert
    assert.nil! args.state.values
    args.state.values += [:a, :b, :c]
    assert.equal! args.state.values, [:a, :b, :c]
  end
  
  def test_open_entity_subtract_array args, assert
    assert.nil! args.state.values
    args.state.values -= [:a, :b, :c]
    assert.equal! args.state.values, []
  end
  
  def test_open_entity_shovel_array args, assert
    assert.nil! args.state.values
    args.state.values << :a
    assert.equal! args.state.values, [:a]
  end
  
  def test_open_entity_enumerate args, assert
    assert.nil! args.state.values
    args.state.values = args.state.values.map_with_index { |i| i }
    assert.equal! args.state.values, []
  
    assert.nil! args.state.values_2
    args.state.values_2 = args.state.values_2.map { |i| i }
    assert.equal! args.state.values_2, []
  
    assert.nil! args.state.values_3
    args.state.values_3 = args.state.values_3.flat_map { |i| i }
    assert.equal! args.state.values_3, []
  end
  
  # hashes
  def test_open_entity_indexer args, assert
    GTK::Entity.__reset_id__!
    assert.nil! args.state.values
    args.state.values[:test] = :value
    assert.equal! args.state.values.to_s, { entity_id: 1, entity_name: :values, entity_keys_by_ref: {}, test: :value }.to_s
  end
  
  # bug
  def test_open_entity_nil_bug args, assert
    GTK::Entity.__reset_id__!
    args.state.foo.a
    args.state.foo.b
    @hello[:foobar]
    assert.nil! args.state.foo.a, "a was not nil."
    # the line below fails
    # assert.nil! args.state.foo.b, "b was not nil."
  end

#+end_src

*** Advanced Debugging - Unit Tests - object_to_primitive_tests.rb
#+begin_src ruby
  # ./samples/10_advanced_debugging/03_unit_tests/object_to_primitive_tests.rb
  class PlayerSpriteForTest
  end
  
  def test_array_to_sprite args, assert
    array = [[0, 0, 100, 100, "test.png"]].sprites
    puts "No exception was thrown. Sweet!"
  end
  
  def test_class_to_sprite args, assert
    array = [PlayerSprite.new].sprites
    assert.true! array.first.is_a?(PlayerSprite)
    puts "No exception was thrown. Sweet!"
  end
  
  $gtk.reset 100
  $gtk.log_level = :off

#+end_src

*** Advanced Debugging - Unit Tests - parsing_tests.rb
#+begin_src ruby
  # ./samples/10_advanced_debugging/03_unit_tests/parsing_tests.rb
  def test_parse_json args, assert
    result = args.gtk.parse_json '{ "name": "John Doe", "aliases": ["JD"] }'
    assert.equal! result, { "name"=>"John Doe", "aliases"=>["JD"] }, "Parsing JSON failed."
  end
  
  def test_parse_xml args, assert
    result = args.gtk.parse_xml <<-S
  <Person id="100">
    <Name>John Doe</Name>
  </Person>
  S
  
   expected = {:type=>:element,
               :name=>nil,
               :children=>[{:type=>:element,
                            :name=>"Person",
                            :children=>[{:type=>:element,
                                         :name=>"Name",
                                         :children=>[{:type=>:content,
                                                      :data=>"John Doe"}]}],
                            :attributes=>{"id"=>"100"}}]}
  
   assert.equal! result, expected, "Parsing xml failed."
  end
  
  $gtk.reset 100
  $gtk.log_level = :off

#+end_src

*** Advanced Debugging - Unit Tests - pretty_format_tests.rb
#+begin_src ruby
  # ./samples/10_advanced_debugging/03_unit_tests/pretty_format_tests.rb
  def H opts
    opts
  end
  
  def A *opts
    opts
  end
  
  def assert_format args, assert, hash, expected
    actual = args.fn.pretty_format hash
    assert.are_equal! actual, expected
  end
  
  def test_pretty_print args, assert
    # =============================
    # hash with single value
    # =============================
    input = (H first_name: "John")
    expected = <<-S
  {:first_name "John"}
  S
    (assert_format args, assert, input, expected)
  
    # =============================
    # hash with two values
    # =============================
    input = (H first_name: "John", last_name: "Smith")
    expected = <<-S
  {:first_name "John"
   :last_name "Smith"}
  S
  
    (assert_format args, assert, input, expected)
  
    # =============================
    # hash with inner hash
    # =============================
    input = (H first_name: "John",
               last_name: "Smith",
               middle_initial: "I",
               so: (H first_name: "Pocahontas",
                      last_name: "Tsenacommacah"),
               friends: (A (H first_name: "Side", last_name: "Kick"),
                           (H first_name: "Tim", last_name: "Wizard")))
    expected = <<-S
  {:first_name "John"
   :last_name "Smith"
   :middle_initial "I"
   :so {:first_name "Pocahontas"
        :last_name "Tsenacommacah"}
   :friends [{:first_name "Side"
              :last_name "Kick"}
             {:first_name "Tim"
              :last_name "Wizard"}]}
  S
  
    (assert_format args, assert, input, expected)
  
    # =============================
    # array with one value
    # =============================
    input = (A 1)
    expected = <<-S
  [1]
  S
    (assert_format args, assert, input, expected)
  
    # =============================
    # array with multiple values
    # =============================
    input = (A 1, 2, 3)
    expected = <<-S
  [1
   2
   3]
  S
    (assert_format args, assert, input, expected)
  
    # =============================
    # array with multiple values hashes
    # =============================
    input = (A (H first_name: "Side", last_name: "Kick"),
               (H first_name: "Tim", last_name: "Wizard"))
    expected = <<-S
  [{:first_name "Side"
    :last_name "Kick"}
   {:first_name "Tim"
    :last_name "Wizard"}]
  S
  
    (assert_format args, assert, input, expected)
  end
  
  def test_nested_nested args, assert
    # =============================
    # nested array in nested hash
    # =============================
    input = (H type: :root,
               text: "Root",
               children: (A (H level: 1,
                               text: "Level 1",
                               children: (A (H level: 2,
                                               text: "Level 2",
                                               children: [])))))
  
    expected = <<-S
  {:type :root
   :text "Root"
   :children [{:level 1
               :text "Level 1"
               :children [{:level 2
                           :text "Level 2"
                           :children []}]}]}
  
  S
  
    (assert_format args, assert, input, expected)
  end
  
  def test_scene args, assert
    script = <<-S
  * Scene 1
  ** Narrator
  They say happy endings don't exist.
  ** Narrator
  They say true love is a lie.
  S
    input = parse_org args, script
    puts (args.fn.pretty_format input)
  end

#+end_src

*** Advanced Debugging - Unit Tests - require_tests.rb
#+begin_src ruby
  # ./samples/10_advanced_debugging/03_unit_tests/require_tests.rb
  def write_src path, src
    $gtk.write_file path, src
  end
  
  write_src 'app/unit_testing_game.rb', <<-S
  module UnitTesting
    class Game
    end
  end
  S
  
  write_src 'lib/unit_testing_lib.rb', <<-S
  module UnitTesting
    class Lib
    end
  end
  S
  
  write_src 'app/nested/unit_testing_nested.rb', <<-S
  module UnitTesting
    class Nested
    end
  end
  S
  
  require 'app/unit_testing_game.rb'
  require 'app/nested/unit_testing_nested.rb'
  require 'lib/unit_testing_lib.rb'
  
  def test_require args, assert
    UnitTesting::Game.new
    UnitTesting::Lib.new
    UnitTesting::Nested.new
    $gtk.exec 'rm ./mygame/app/unit_testing_game.rb'
    $gtk.exec 'rm ./mygame/app/nested/unit_testing_nested.rb'
    $gtk.exec 'rm ./mygame/lib/unit_testing_lib.rb'
    assert.ok!
  end

#+end_src

*** Advanced Debugging - Unit Tests - serialize_deserialize_tests.rb
#+begin_src ruby
  # ./samples/10_advanced_debugging/03_unit_tests/serialize_deserialize_tests.rb
  def test_serialize args, assert
    GTK::Entity.__reset_id__!
    args.state.player_one = "test"
    result = args.gtk.serialize_state args.state
    assert.equal! result, "{:entity_id=>4, :entity_keys_by_ref=>{}, :tick_count=>-1, :player_one=>\"test\"}"
  
    GTK::Entity.__reset_id__!
    args.gtk.write_file 'state.txt', ''
    result = args.gtk.serialize_state 'state.txt', args.state
    assert.equal! result, "{:entity_id=>4, :entity_keys_by_ref=>{}, :tick_count=>-1, :player_one=>\"test\"}"
  end
  
  def test_deserialize args, assert
    GTK::Entity.__reset_id__!
    result = args.gtk.deserialize_state '{:entity_id=>3, :tick_count=>-1, :player_one=>"test"}'
    assert.equal! result.player_one, "test"
  
    GTK::Entity.__reset_id__!
    args.gtk.write_file 'state.txt',  '{:entity_id=>3, :tick_count=>-1, :player_one=>"test"}'
    result = args.gtk.deserialize_state 'state.txt'
    assert.equal! result.player_one, "test"
  end
  
  def test_very_large_serialization args, assert
    GTK::Entity.__reset_id__!
    size = 3000
    size.map_with_index do |i|
      args.state.send("k#{i}=".to_sym, i)
    end
  
    result = args.gtk.serialize_state args.state
    assert.true! (args.gtk.console.log.join.include? "unlikely a string this large will deserialize correctly")
  end
  
  def test_strict_entity_serialization args, assert
    GTK::Entity.__reset_id__!
    args.state.player_one = args.state.new_entity(:player, name: "Ryu")
    args.state.player_two = args.state.new_entity_strict(:player_strict, name: "Ken")
  
    serialized_state = args.gtk.serialize_state args.state
    assert.equal! serialized_state, '{:entity_id=>1, :entity_keys_by_ref=>{}, :tick_count=>-1, :player_one=>{:entity_id=>1, :entity_name=>:player, :entity_keys_by_ref=>{}, :entity_type=>:player, :created_at=>-1, :global_created_at=>-1, :name=>"Ryu"}, :player_two=>{:entity_id=>3, :entity_name=>:player_strict, :entity_type=>:player_strict, :created_at=>-1, :global_created_at_elapsed=>-1, :entity_strict=>true, :entity_keys_by_ref=>{:entity_type=>:entity_name, :global_created_at_elapsed=>:created_at}, :name=>"Ken"}}'
  
    GTK::Entity.__reset_id__!
    deserialize_state = args.gtk.deserialize_state serialized_state
  
    assert.equal! args.state.player_one.name, deserialize_state.player_one.name
    assert.true! args.state.player_one.is_a? GTK::OpenEntity
  
    assert.equal! args.state.player_two.name, deserialize_state.player_two.name
    assert.true! args.state.player_two.is_a? GTK::StrictEntity
  end
  
  def test_strict_entity_serialization_with_nil args, assert
    GTK::Entity.__reset_id__!
    args.state.player_one = args.state.new_entity(:player, name: "Ryu")
    args.state.player_two = args.state.new_entity_strict(:player_strict, name: "Ken", blood_type: nil)
  
    serialized_state = args.gtk.serialize_state args.state
    assert.equal! serialized_state, '{:entity_id=>7, :entity_keys_by_ref=>{}, :tick_count=>-1, :player_one=>{:entity_id=>1, :entity_name=>:player, :entity_keys_by_ref=>{}, :entity_type=>:player, :created_at=>-1, :global_created_at=>-1, :name=>"Ryu"}, :player_two=>{:entity_id=>2, :entity_name=>:player_strict, :entity_type=>:player_strict, :created_at=>-1, :global_created_at_elapsed=>-1, :entity_strict=>true, :entity_keys_by_ref=>{:entity_type=>:entity_name, :global_created_at_elapsed=>:created_at}, :name=>"Ken", :blood_type=>nil}}'
  
    GTK::Entity.__reset_id__!
    deserialized_state = args.gtk.deserialize_state serialized_state
  
    assert.equal! args.state.player_one.name, deserialized_state.player_one.name
    assert.true! args.state.player_one.is_a? GTK::OpenEntity
  
    assert.equal! args.state.player_two.name, deserialized_state.player_two.name
    assert.equal! args.state.player_two.blood_type, deserialized_state.player_two.blood_type
    assert.equal! deserialized_state.player_two.blood_type, nil
    assert.true! args.state.player_two.is_a? GTK::StrictEntity
  
    deserialized_state.player_two.blood_type = :O
    assert.equal! deserialized_state.player_two.blood_type, :O
  end
  
  def test_multiple_strict_entities args, assert
    GTK::Entity.__reset_id__!
    args.state.player = args.state.new_entity_strict(:player_one, name: "Ryu")
    args.state.enemy = args.state.new_entity_strict(:enemy, name: "Bison", other_property: 'extra mean')
  
    serialized_state = args.gtk.serialize_state args.state
  
    GTK::Entity.__reset_id__!
    deserialized_state = args.gtk.deserialize_state serialized_state
  
    assert.equal! deserialized_state.player.name, "Ryu"
    assert.equal! deserialized_state.enemy.other_property, "extra mean"
  end
  
  def test_by_reference_state args, assert
    GTK::Entity.__reset_id__!
    args.state.a = { name: "Jane Doe" }
    args.state.b = args.state.a
    assert.equal! args.state.a.object_id, args.state.b.object_id
    serialized_state = args.gtk.serialize_state args.state
  
    GTK::Entity.__reset_id__!
    deserialized_state = args.gtk.deserialize_state serialized_state
    assert.equal! deserialized_state.a.object_id, deserialized_state.b.object_id
  end
  
  def test_by_reference_state_strict_entities args, assert
    GTK::Entity.__reset_id__!
    args.state.a = { name: "Jane Doe" }
    args.state.strict_entity = args.state.new_entity_strict(:couple) do |e|
      e.one = args.state.new_entity_strict(:person, name: "Jane")
      e.two = e.one
    end
    assert.equal! args.state.strict_entity.one, args.state.strict_entity.two
    serialized_state = args.gtk.serialize_state args.state
  
    GTK::Entity.__reset_id__!
    deserialized_state = args.gtk.deserialize_state serialized_state
    assert.equal! deserialized_state.strict_entity.one, deserialized_state.strict_entity.two
  end
  
  def test_serialization_excludes_thrash_count args, assert
    GTK::Entity.__reset_id__!
    args.state.player.name = "Ryu"
    # force a nil pun
    if args.state.player.age > 30
    end
    assert.equal! args.state.player.as_hash[:__thrash_count__][:>], 1
    result = args.gtk.serialize_state args.state
    assert.false! (result.include? "__thrash_count__"),
                  "The __thrash_count__ key exists in state when it shouldn't have."
  end

#+end_src

*** Advanced Debugging - Unit Tests - state_serialization_experimental_tests.rb
#+begin_src ruby
  # ./samples/10_advanced_debugging/03_unit_tests/state_serialization_experimental_tests.rb
  MAX_CODE_GEN_LENGTH = 50
  
  # NOTE: This is experimental/advanced stuff.
  def needs_partitioning? target
    target[:value].to_s.length > MAX_CODE_GEN_LENGTH
  end
  
  def partition target
    return [] unless needs_partitioning? target
    if target[:value].is_a? GTK::OpenEntity
      target[:value] = target[:value].hash
    end
  
    results = []
    idx = 0
    left, right = target[:value].partition do
      idx += 1
      idx.even?
    end
    left, right = Hash[left], Hash[right]
    left = { value: left }
    right = { value: right}
    [left, right]
  end
  
  def add_partition target, path, aggregate, final_result
    partitions = partition target
    partitions.each do |part|
      if needs_partitioning? part
        if part[:value].keys.length == 1
          first_key = part[:value].keys[0]
          new_part = { value: part[:value][first_key] }
          path.push first_key
          add_partition new_part, path, aggregate, final_result
          path.pop
        else
          add_partition part, path, aggregate, final_result
        end
      else
        final_result << { value: { __path__: [*path] } }
        final_result << { value: part[:value] }
      end
    end
  end
  
  def state_to_string state
    parts_queue = []
    final_queue = []
    add_partition({ value: state.hash },
                  [],
                  parts_queue,
                  final_queue)
    final_queue.reject {|i| i[:value].keys.length == 0}.map do |i|
      i[:value].to_s
    end.join("\n#==================================================#\n")
  end
  
  def state_from_string string
    Kernel.eval("$load_data = {}")
    lines = string.split("\n#==================================================#\n")
    lines.each do |l|
      puts "todo: #{l}"
    end
  
    GTK::OpenEntity.parse_from_hash $load_data
  end
  
  def test_save_and_load args, assert
    args.state.item_1.name = "Jane"
    string = state_to_string args.state
    state = state_from_string string
    assert.equal! args.state.item_1.name, state.item_1.name
  end
  
  def test_save_and_load_big args, assert
    size = 1000
    size.map_with_index do |i|
      args.state.send("k#{i}=".to_sym, i)
    end
  
    string = state_to_string args.state
    state = state_from_string string
    size.map_with_index do |i|
      assert.equal! args.state.send("k#{i}".to_sym), state.send("k#{i}".to_sym)
      assert.equal! args.state.send("k#{i}".to_sym), i
      assert.equal! state.send("k#{i}".to_sym), i
    end
  end
  
  def test_save_and_load_big_nested args, assert
    args.state.player_one.friend.nested_hash.k0 = 0
    args.state.player_one.friend.nested_hash.k1 = 1
    args.state.player_one.friend.nested_hash.k2 = 2
    args.state.player_one.friend.nested_hash.k3 = 3
    args.state.player_one.friend.nested_hash.k4 = 4
    args.state.player_one.friend.nested_hash.k5 = 5
    args.state.player_one.friend.nested_hash.k6 = 6
    args.state.player_one.friend.nested_hash.k7 = 7
    args.state.player_one.friend.nested_hash.k8 = 8
    args.state.player_one.friend.nested_hash.k9 = 9
    string = state_to_string args.state
    state = state_from_string string
  end
  
  $gtk.reset 100
  $gtk.log_level = :off

#+end_src

*** Advanced Debugging - Unit Tests - suggest_autocompletion_tests.rb
#+begin_src ruby
  # ./samples/10_advanced_debugging/03_unit_tests/suggest_autocompletion_tests.rb
  def default_suggest_autocompletion args
    {
      index: 4,
      text: "args.",
      __meta__: {
        other_options: [
          {
            index: Fixnum,
            file: "app/main.rb"
          }
        ]
      }
    }
  end
  
  def assert_completion source, *expected
    results = suggest_autocompletion text:  (source.strip.gsub  ":cursor", ""),
                                     index: (source.strip.index ":cursor")
  
    puts results
  end
  
  def test_args_completion args, assert
    $gtk.write_file_root "autocomplete.txt", ($gtk.suggest_autocompletion text: <<-S, index: 128).join("\n")
  require 'app/game.rb'
  
  def tick args
    args.gtk.suppress_mailbox = false
    $game ||= Game.new
    $game.args = args
    $game.args.
    $game.tick
  end
  S
  
    puts "contents:"
    puts ($gtk.read_file "autocomplete.txt")
  end

#+end_src

*** Http - Retrieve Images - main.rb
#+begin_src ruby
  # ./samples/11_http/01_retrieve_images/app/main.rb
  $gtk.register_cvar 'app.warn_seconds', "seconds to wait before starting", :uint, 11
  
  def tick args
    args.outputs.background_color = [0, 0, 0]
  
    # Show a warning at the start.
    args.state.warning_debounce ||= args.cvars['app.warn_seconds'].value * 60
    if args.state.warning_debounce > 0
      args.state.warning_debounce -= 1
      args.outputs.labels << [640, 600, "This app shows random images from the Internet.", 10, 1, 255, 255, 255]
      args.outputs.labels << [640, 500, "Quit in the next few seconds if this is a problem.", 10, 1, 255, 255, 255]
      args.outputs.labels << [640, 350, "#{(args.state.warning_debounce / 60.0).to_i}", 10, 1, 255, 255, 255]
      return
    end
  
    args.state.download_debounce ||= 0   # start immediately, reset to non zero later.
    args.state.photos ||= []
  
    # Put a little pause between each download.
    if args.state.download.nil?
      if args.state.download_debounce > 0
        args.state.download_debounce -= 1
      else
        args.state.download = $gtk.http_get 'https://picsum.photos/200/300.jpg'
      end
    end
  
    if !args.state.download.nil?
      if args.state.download[:complete]
        if args.state.download[:http_response_code] == 200
          fname = "sprites/#{args.state.photos.length}.jpg"
          $gtk.write_file fname, args.state.download[:response_data]
          args.state.photos << [ 100 + rand(1080), 500 - rand(480), fname, rand(80) - 40 ]
        end
        args.state.download = nil
        args.state.download_debounce = (rand(3) + 2) * 60
      end
    end
  
    # draw any downloaded photos...
    args.state.photos.each { |i|
      args.outputs.primitives << [i[0], i[1], 200, 300, i[2], i[3]].sprite
    }
  
    # Draw a download progress bar...
    args.outputs.primitives << [0, 0, 1280, 30, 0, 0, 0, 255].solid
    if !args.state.download.nil?
      br = args.state.download[:response_read]
      total = args.state.download[:response_total]
      if total != 0
        pct = br.to_f / total.to_f
        args.outputs.primitives << [0, 0, 1280 * pct, 30, 0, 0, 255, 255].solid
      end
    end
  end

#+end_src

*** Http - In Game Web Server Http Get - main.rb
#+begin_src ruby
  # ./samples/11_http/02_in_game_web_server_http_get/app/main.rb
  def tick args
    args.state.port ||= 3000
    args.state.reqnum ||= 0
    # by default the embedded webserver runs on port 9001 (the port number is over 9000) and is disabled in a production build
    # to enable the http server in a production build, you need to manually start
    # the server up:
    args.gtk.start_server! port: args.state.port, enable_in_prod: true
    args.outputs.background_color = [0, 0, 0]
    args.outputs.labels << [640, 600, "Point your web browser at http://localhost:#{args.state.port}/", 10, 1, 255, 255, 255]
  
    args.inputs.http_requests.each { |req|
      puts("METHOD: #{req.method}");
      puts("URI: #{req.uri}");
      puts("HEADERS:");
      req.headers.each { |k,v| puts("  #{k}: #{v}") }
  
      if (req.uri == '/')
        # headers and body can be nil if you don't care about them.
        # If you don't set the Content-Type, it will default to
        #  "text/html; charset=utf-8".
        # Don't set Content-Length; we'll ignore it and calculate it for you
        args.state.reqnum += 1
        req.respond 200, "<html><head><title>hello</title></head><body><h1>This #{req.method} was request number #{args.state.reqnum}!</h1></body></html>\n", { 'X-DRGTK-header' => 'Powered by DragonRuby!' }
      else
        req.reject
      end
    }
  end

#+end_src

*** Http - In Game Web Server Http Post - main.rb
#+begin_src ruby
  # ./samples/11_http/03_in_game_web_server_http_post/app/main.rb
  def tick args
    # defaults
    args.state.post_button      = args.layout.rect(row: 0, col: 0, w: 5, h: 1).merge(text: "execute http_post")
    args.state.post_body_button = args.layout.rect(row: 1, col: 0, w: 5, h: 1).merge(text: "execute http_post_body")
    args.state.request_to_s ||= ""
    args.state.request_body ||= ""
  
    # render
    args.state.post_button.yield_self do |b|
      args.outputs.borders << b
      args.outputs.labels  << b.merge(text: b.text,
                                      y:    b.y + 30,
                                      x:    b.x + 10)
    end
  
    args.state.post_body_button.yield_self do |b|
      args.outputs.borders << b
      args.outputs.labels  << b.merge(text: b.text,
                                      y:    b.y + 30,
                                      x:    b.x + 10)
    end
  
    draw_label args, 0,  6, "Request:", args.state.request_to_s
    draw_label args, 0, 14, "Request Body Unaltered:", args.state.request_body
  
    # input
    if args.inputs.mouse.click
      # ============= HTTP_POST =============
      if (args.inputs.mouse.inside_rect? args.state.post_button)
        # ========= DATA TO SEND ===========
        form_fields = { "userId" => "#{Time.now.to_i}" }
        # ==================================
  
        args.gtk.http_post "http://localhost:9001/testing",
                           form_fields,
                           ["Content-Type: application/x-www-form-urlencoded"]
  
        args.gtk.notify! "http_post"
      end
  
      # ============= HTTP_POST_BODY =============
      if (args.inputs.mouse.inside_rect? args.state.post_body_button)
        # =========== DATA TO SEND ==============
        json = "{ \"userId\": \"#{Time.now.to_i}\"}"
        # ==================================
  
        args.gtk.http_post_body "http://localhost:9001/testing",
                                json,
                                ["Content-Type: application/json", "Content-Length: #{json.length}"]
  
        args.gtk.notify! "http_post_body"
      end
    end
  
    # calc
    args.inputs.http_requests.each do |r|
      puts "#{r}"
      if r.uri == "/testing"
        puts r
        args.state.request_to_s = "#{r}"
        args.state.request_body = r.raw_body
        r.respond 200, "ok"
      end
    end
  end
  
  def draw_label args, row, col, header, text
    label_pos = args.layout.rect(row: row, col: col, w: 0, h: 0)
    args.outputs.labels << "#{header}\n\n#{text}".wrapped_lines(80).map_with_index do |l, i|
      { x: label_pos.x, y: label_pos.y - (i * 15), text: l, size_enum: -2 }
    end
  end

#+end_src

*** C Extensions - Basics - main.rb
#+begin_src ruby
  # ./samples/12_c_extensions/01_basics/app/main.rb
  $gtk.ffi_misc.gtk_dlopen("ext")
  include FFI::CExt
  
  def tick args
    args.outputs.labels  << [640, 500, "mouse.x = #{args.mouse.x.to_i}", 5, 1]
    args.outputs.labels  << [640, 460, "square(mouse.x) = #{square(args.mouse.x.to_i)}", 5, 1]
    args.outputs.labels  << [640, 420, "mouse.y = #{args.mouse.y.to_i}", 5, 1]
    args.outputs.labels  << [640, 380, "square(mouse.y) = #{square(args.mouse.y.to_i)}", 5, 1]
  end
  

#+end_src

*** C Extensions - Intermediate - main.rb
#+begin_src ruby
  # ./samples/12_c_extensions/02_intermediate/app/main.rb
  $gtk.ffi_misc.gtk_dlopen("ext")
  include FFI::RE
  
  def split_words(input)
    words = []
    last = IntPointer.new
    re = re_compile("\\w+")
    first = re_matchp(re, input, last)
    while first != -1
      words << input.slice(first, last.value)
      input = input.slice(last.value + first, input.length)
      first = re_matchp(re, input, last)
    end
    words
  end
  
  def tick args
    args.outputs.labels  << [640, 500, split_words("hello, dragonriders!").join(' '), 5, 1]
  end

#+end_src

*** C Extensions - Native Pixel Arrays - main.rb
#+begin_src ruby
  # ./samples/12_c_extensions/03_native_pixel_arrays/app/main.rb
  $gtk.ffi_misc.gtk_dlopen("ext")
  include FFI::CExt
  
  def tick args
    args.state.rotation ||= 0
  
    update_scanner_texture   # this calls into a C extension!
  
    # New/changed pixel arrays get uploaded to the GPU before we render
    #  anything. At that point, they can be scaled, rotated, and otherwise
    #  used like any other sprite.
    w = 100
    h = 100
    x = (1280 - w) / 2
    y = (720 - h) / 2
    args.outputs.background_color = [64, 0, 128]
    args.outputs.primitives << [x, y, w, h, :scanner, args.state.rotation].sprite
    args.state.rotation += 1
  
    args.outputs.primitives << args.gtk.current_framerate_primitives
  end
  

#+end_src

*** C Extensions - Handcrafted Extension - main.rb
#+begin_src ruby
  # ./samples/12_c_extensions/04_handcrafted_extension/app/main.rb
  $gtk.ffi_misc.gtk_dlopen("ext")
  include FFI::CExt
  
  puts Adder.new.add_all(1, 2, 3, [4, 5, 6.0])
  
  def tick args
  end

#+end_src

*** C Extensions - Handcrafted Extension - license.txt
#+begin_src ruby
  # ./samples/12_c_extensions/04_handcrafted_extension/license.txt
  Copyright 2022 DragonRuby LLC
  
  MIT License
  
  Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
  
  The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
  
  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

#+end_src

*** Path Finding Algorithms - Breadth First Search - main.rb
#+begin_src ruby
  # ./samples/13_path_finding_algorithms/01_breadth_first_search/app/main.rb
  # A visual demonstration of a breadth first search
  # Inspired by https://www.redblobgames.com/pathfinding/a-star/introduction.html
  
  # An animation that can respond to user input in real time
  
  # A breadth first search expands in all directions one step at a time
  # The frontier is a queue of cells to be expanded from
  # The visited hash allows quick lookups of cells that have been expanded from
  # The walls hash allows quick lookup of whether a cell is a wall
  
  # The breadth first search starts by adding the red star to the frontier array
  # and marking it as visited
  # Each step a cell is removed from the front of the frontier array (queue)
  # Unless the neighbor is a wall or visited, it is added to the frontier array
  # The neighbor is then marked as visited
  
  # The frontier is blue
  # Visited cells are light brown
  # Walls are camo green
  # Even when walls are visited, they will maintain their wall color
  
  # The star can be moved by clicking and dragging
  # Walls can be added and removed by clicking and dragging
  
  class BreadthFirstSearch
    attr_gtk
  
    def initialize(args)
      # Variables to edit the size and appearance of the grid
      # Freely customizable to user's liking
      args.state.grid.width     = 30
      args.state.grid.height    = 15
      args.state.grid.cell_size = 40
  
      # Stores which step of the animation is being rendered
      # When the user moves the star or messes with the walls,
      # the breadth first search is recalculated up to this step
      args.state.anim_steps = 0
  
      # At some step the animation will end,
      # and further steps won't change anything (the whole grid will be explored)
      # This step is roughly the grid's width * height
      # When anim_steps equals max_steps no more calculations will occur
      # and the slider will be at the end
      args.state.max_steps  = args.state.grid.width * args.state.grid.height
  
      # Whether the animation should play or not
      # If true, every tick moves anim_steps forward one
      # Pressing the stepwise animation buttons will pause the animation
      args.state.play       = true
  
      # The location of the star and walls of the grid
      # They can be modified to have a different initial grid
      # Walls are stored in a hash for quick look up when doing the search
      args.state.star       = [0, 0]
      args.state.walls      = {
        [3, 3] => true,
        [3, 4] => true,
        [3, 5] => true,
        [3, 6] => true,
        [3, 7] => true,
        [3, 8] => true,
        [3, 9] => true,
        [3, 10] => true,
        [3, 11] => true,
        [4, 3] => true,
        [4, 4] => true,
        [4, 5] => true,
        [4, 6] => true,
        [4, 7] => true,
        [4, 8] => true,
        [4, 9] => true,
        [4, 10] => true,
        [4, 11] => true,
  
        [13, 0] => true,
        [13, 1] => true,
        [13, 2] => true,
        [13, 3] => true,
        [13, 4] => true,
        [13, 5] => true,
        [13, 6] => true,
        [13, 7] => true,
        [13, 8] => true,
        [13, 9] => true,
        [13, 10] => true,
        [14, 0] => true,
        [14, 1] => true,
        [14, 2] => true,
        [14, 3] => true,
        [14, 4] => true,
        [14, 5] => true,
        [14, 6] => true,
        [14, 7] => true,
        [14, 8] => true,
        [14, 9] => true,
        [14, 10] => true,
  
        [21, 8] => true,
        [21, 9] => true,
        [21, 10] => true,
        [21, 11] => true,
        [21, 12] => true,
        [21, 13] => true,
        [21, 14] => true,
        [22, 8] => true,
        [22, 9] => true,
        [22, 10] => true,
        [22, 11] => true,
        [22, 12] => true,
        [22, 13] => true,
        [22, 14] => true,
        [23, 8] => true,
        [23, 9] => true,
        [24, 8] => true,
        [24, 9] => true,
        [25, 8] => true,
        [25, 9] => true,
      }
  
      # Variables that are used by the breadth first search
      # Storing cells that the search has visited, prevents unnecessary steps
      # Expanding the frontier of the search in order makes the search expand
      # from the center outward
      args.state.visited    = {}
      args.state.frontier   = []
  
  
      # What the user is currently editing on the grid
      # Possible values are: :none, :slider, :star, :remove_wall, :add_wall
  
      # We store this value, because we want to remember the value even when
      # the user's cursor is no longer over what they're interacting with, but
      # they are still clicking down on the mouse.
      args.state.click_and_drag = :none
  
      # Store the rects of the buttons that control the animation
      # They are here for user customization
      # Editing these might require recentering the text inside them
      # Those values can be found in the render_button methods
      args.state.buttons.left   = [450, 600, 50, 50]
      args.state.buttons.center = [500, 600, 200, 50]
      args.state.buttons.right  = [700, 600, 50, 50]
  
      # The variables below are related to the slider
      # They allow the user to customize them
      # They also give a central location for the render and input methods to get
      # information from
      # x & y are the coordinates of the leftmost part of the slider line
      args.state.slider.x = 400
      args.state.slider.y = 675
      # This is the width of the line
      args.state.slider.w = 360
      # This is the offset for the circle
      # Allows the center of the circle to be on the line,
      # as opposed to the upper right corner
      args.state.slider.offset = 20
      # This is the spacing between each of the notches on the slider
      # Notches are places where the circle can rest on the slider line
      # There needs to be a notch for each step before the maximum number of steps
      args.state.slider.spacing = args.state.slider.w.to_f / args.state.max_steps.to_f
    end
  
    # This method is called every frame/tick
    # Every tick, the current state of the search is rendered on the screen,
    # User input is processed, and
    # The next step in the search is calculated
    def tick
      render
      input
      # If animation is playing, and max steps have not been reached
      # Move the search a step forward
      if state.play && state.anim_steps < state.max_steps
        # Variable that tells the program what step to recalculate up to
        state.anim_steps += 1
        calc
      end
    end
  
    # Draws everything onto the screen
    def render
      render_buttons
      render_slider
  
      render_background
      render_visited
      render_frontier
      render_walls
      render_star
    end
  
    # The methods below subdivide the task of drawing everything to the screen
  
    # Draws the buttons that control the animation step and state
    def render_buttons
      render_left_button
      render_center_button
      render_right_button
    end
  
    # Draws the button which steps the search backward
    # Shows the user where to click to move the search backward
    def render_left_button
      # Draws the gray button, and a black border
      # The border separates the buttons visually
      outputs.solids  << [buttons.left, gray]
      outputs.borders << [buttons.left, black]
  
      # Renders an explanatory label in the center of the button
      # Explains to the user what the button does
      # If the button size is changed, the label might need to be edited as well
      # to keep the label in the center of the button
      label_x = buttons.left.x + 20
      label_y = buttons.left.y + 35
      outputs.labels  << [label_x, label_y, "<"]
    end
  
    def render_center_button
      # Draws the gray button, and a black border
      # The border separates the buttons visually
      outputs.solids  << [buttons.center, gray]
      outputs.borders << [buttons.center, black]
  
      # Renders an explanatory label in the center of the button
      # Explains to the user what the button does
      # If the button size is changed, the label might need to be edited as well
      # to keep the label in the center of the button
      label_x    = buttons.center.x + 37
      label_y    = buttons.center.y + 35
      label_text = state.play ? "Pause Animation" : "Play Animation"
      outputs.labels << [label_x, label_y, label_text]
    end
  
    def render_right_button
      # Draws the gray button, and a black border
      # The border separates the buttons visually
      outputs.solids  << [buttons.right, gray]
      outputs.borders << [buttons.right, black]
  
      # Renders an explanatory label in the center of the button
      # Explains to the user what the button does
      label_x = buttons.right.x + 20
      label_y = buttons.right.y + 35
      outputs.labels  << [label_x, label_y, ">"]
    end
  
    # Draws the slider so the user can move it and see the progress of the search
    def render_slider
      # Using primitives hides the line under the white circle of the slider
      # Draws the line
      outputs.primitives << [slider.x, slider.y, slider.x + slider.w, slider.y].line
      # The circle needs to be offset so that the center of the circle
      # overlaps the line instead of the upper right corner of the circle
      # The circle's x value is also moved based on the current seach step
      circle_x = (slider.x - slider.offset) + (state.anim_steps * slider.spacing)
      circle_y = (slider.y - slider.offset)
      circle_rect = [circle_x, circle_y, 37, 37]
      outputs.primitives << [circle_rect, 'circle-white.png'].sprite
    end
  
    # Draws what the grid looks like with nothing on it
    def render_background
      render_unvisited
      render_grid_lines
    end
  
    # Draws a rectangle the size of the entire grid to represent unvisited cells
    def render_unvisited
      outputs.solids << [scale_up([0, 0, grid.width, grid.height]), unvisited_color]
    end
  
    # Draws grid lines to show the division of the grid into cells
    def render_grid_lines
      for x in 0..grid.width
        outputs.lines << vertical_line(x)
      end
  
      for y in 0..grid.height
        outputs.lines << horizontal_line(y)
      end
    end
  
    # Easy way to draw vertical lines given an index
    def vertical_line column
      scale_up([column, 0, column, grid.height])
    end
  
    # Easy way to draw horizontal lines given an index
    def horizontal_line row
      scale_up([0, row, grid.width, row])
    end
  
    # Draws the area that is going to be searched from
    # The frontier is the most outward parts of the search
    def render_frontier
      outputs.solids << state.frontier.map do |cell|
        [scale_up([cell.x, cell.y]), frontier_color]
      end
    end
  
    # Draws the walls
    def render_walls
      outputs.solids << state.walls.map do |wall|
        [scale_up([wall.x, wall.y]), wall_color]
      end
    end
  
    # Renders cells that have been searched in the appropriate color
    def render_visited
      outputs.solids << state.visited.map do |cell|
        [scale_up([cell.x, cell.y]), visited_color]
      end
    end
  
    # Renders the star
    def render_star
      outputs.sprites << [scale_up(state.star), 'star.png']
    end
  
    # In code, the cells are represented as 1x1 rectangles
    # When drawn, the cells are larger than 1x1 rectangles
    # This method is used to scale up cells, and lines
    # Objects are scaled up according to the grid.cell_size variable
    # This allows for easy customization of the visual scale of the grid
    def scale_up(cell)
      # Prevents the original value of cell from being edited
      cell = cell.clone
  
      # If cell is just an x and y coordinate
      if cell.size == 2
        # Add a width and height of 1
        cell << 1
        cell << 1
      end
  
      # Scale all the values up
      cell.map! { |value| value * grid.cell_size }
  
      # Returns the scaled up cell
      cell
    end
  
    # This method processes user input every tick
    # This method allows the user to use the buttons, slider, and edit the grid
    # There are 2 types of input:
    #   Button Input
    #   Click and Drag Input
    #
    #   Button Input is used for the backward step and forward step buttons
    #   Input is detected by mouse up within the bounds of the rect
    #
    #   Click and Drag Input is used for moving the star, adding walls,
    #   removing walls, and the slider
    #
    #   When the mouse is down on the star, the click_and_drag variable is set to :star
    #   While click_and_drag equals :star, the cursor's position is used to calculate the
    #   appropriate drag behavior
    #
    #   When the mouse goes up click_and_drag is set to :none
    #
    #   A variable has to be used because the star has to continue being edited even
    #   when the cursor is no longer over the star
    #
    #   Similar things occur for the other Click and Drag inputs
    def input
      # Checks whether any of the buttons are being clicked
      input_buttons
  
      # The detection and processing of click and drag inputs are separate
      # The program has to remember that the user is dragging an object
      # even when the mouse is no longer over that object
      detect_click_and_drag
      process_click_and_drag
    end
  
    # Detects and Process input for each button
    def input_buttons
      input_left_button
      input_center_button
      input_next_step_button
    end
  
    # Checks if the previous step button is clicked
    # If it is, it pauses the animation and moves the search one step backward
    def input_left_button
      if left_button_clicked?
        state.play = false
        state.anim_steps -= 1
        recalculate
      end
    end
  
    # Controls the play/pause button
    # Inverses whether the animation is playing or not when clicked
    def input_center_button
      if center_button_clicked? or inputs.keyboard.key_down.space
        state.play = !state.play
      end
    end
  
    # Checks if the next step button is clicked
    # If it is, it pauses the animation and moves the search one step forward
    def input_next_step_button
      if right_button_clicked?
        state.play = false
        state.anim_steps += 1
        calc
      end
    end
  
    # Determines what the user is editing and stores the value
    # Storing the value allows the user to continue the same edit as long as the
    # mouse left click is held
    def detect_click_and_drag
      if inputs.mouse.up
        state.click_and_drag = :none
      elsif star_clicked?
        state.click_and_drag = :star
      elsif wall_clicked?
        state.click_and_drag = :remove_wall
      elsif grid_clicked?
        state.click_and_drag = :add_wall
      elsif slider_clicked?
        state.click_and_drag = :slider
      end
    end
  
    # Processes click and drag based on what the user is currently dragging
    def process_click_and_drag
      if state.click_and_drag == :star
        input_star
      elsif state.click_and_drag == :remove_wall
        input_remove_wall
      elsif state.click_and_drag == :add_wall
        input_add_wall
      elsif state.click_and_drag == :slider
        input_slider
      end
    end
  
    # Moves the star to the grid closest to the mouse
    # Only recalculates the search if the star changes position
    # Called whenever the user is editing the star (puts mouse down on star)
    def input_star
      old_star = state.star.clone
      state.star = cell_closest_to_mouse
      unless old_star == state.star
        recalculate
      end
    end
  
    # Removes walls that are under the cursor
    def input_remove_wall
      # The mouse needs to be inside the grid, because we only want to remove walls
      # the cursor is directly over
      # Recalculations should only occur when a wall is actually deleted
      if mouse_inside_grid?
        if state.walls.has_key?(cell_closest_to_mouse)
          state.walls.delete(cell_closest_to_mouse)
          recalculate
        end
      end
    end
  
    # Adds walls at cells under the cursor
    def input_add_wall
      if mouse_inside_grid?
        unless state.walls.has_key?(cell_closest_to_mouse)
          state.walls[cell_closest_to_mouse] = true
          recalculate
        end
      end
    end
  
    # This method is called when the user is editing the slider
    # It pauses the animation and moves the white circle to the closest integer point
    # on the slider
    # Changes the step of the search to be animated
    def input_slider
      state.play = false
      mouse_x = inputs.mouse.point.x
  
      # Bounds the mouse_x to the closest x value on the slider line
      mouse_x = slider.x if mouse_x < slider.x
      mouse_x = slider.x + slider.w if mouse_x > slider.x + slider.w
  
      # Sets the current search step to the one represented by the mouse x value
      # The slider's circle moves due to the render_slider method using anim_steps
      state.anim_steps = ((mouse_x - slider.x) / slider.spacing).to_i
  
      recalculate
    end
  
    # Whenever the user edits the grid,
    # The search has to be recalculated upto the current step
    # with the current grid as the initial state of the grid
    def recalculate
      # Resets the search
      state.frontier = []
      state.visited = {}
  
      # Moves the animation forward one step at a time
      state.anim_steps.times { calc }
    end
  
  
    # This method moves the search forward one step
    # When the animation is playing it is called every tick
    # And called whenever the current step of the animation needs to be recalculated
  
    # Moves the search forward one step
    # Parameter called_from_tick is true if it is called from the tick method
    # It is false when the search is being recalculated after user editing the grid
    def calc
  
      # The setup to the search
      # Runs once when the there is no frontier or visited cells
      if state.frontier.empty? && state.visited.empty?
        state.frontier << state.star
        state.visited[state.star] = true
      end
  
      # A step in the search
      unless state.frontier.empty?
        # Takes the next frontier cell
        new_frontier = state.frontier.shift
        # For each of its neighbors
        adjacent_neighbors(new_frontier).each do |neighbor|
          # That have not been visited and are not walls
          unless state.visited.has_key?(neighbor) || state.walls.has_key?(neighbor)
            # Add them to the frontier and mark them as visited
            state.frontier << neighbor
            state.visited[neighbor] = true
          end
        end
      end
    end
  
  
    # Returns a list of adjacent cells
    # Used to determine what the next cells to be added to the frontier are
    def adjacent_neighbors(cell)
      neighbors = []
  
      neighbors << [cell.x, cell.y + 1] unless cell.y == grid.height - 1
      neighbors << [cell.x + 1, cell.y] unless cell.x == grid.width - 1
      neighbors << [cell.x, cell.y - 1] unless cell.y == 0
      neighbors << [cell.x - 1, cell.y] unless cell.x == 0
  
      neighbors
    end
  
    # When the user grabs the star and puts their cursor to the far right
    # and moves up and down, the star is supposed to move along the grid as well
    # Finding the cell closest to the mouse helps with this
    def cell_closest_to_mouse
      # Closest cell to the mouse
      x = (inputs.mouse.point.x / grid.cell_size).to_i
      y = (inputs.mouse.point.y / grid.cell_size).to_i
      # Bound x and y to the grid
      x = grid.width - 1 if x > grid.width - 1
      y = grid.height - 1 if y > grid.height - 1
      # Return closest cell
      [x, y]
    end
  
    # These methods detect when the buttons are clicked
    def left_button_clicked?
      inputs.mouse.up && inputs.mouse.point.inside_rect?(buttons.left)
    end
  
    def center_button_clicked?
      inputs.mouse.up && inputs.mouse.point.inside_rect?(buttons.center)
    end
  
    def right_button_clicked?
      inputs.mouse.up && inputs.mouse.point.inside_rect?(buttons.right)
    end
  
    # Signal that the user is going to be moving the slider
    # Is the mouse down on the circle of the slider?
    def slider_clicked?
      circle_x = (slider.x - slider.offset) + (state.anim_steps * slider.spacing)
      circle_y = (slider.y - slider.offset)
      circle_rect = [circle_x, circle_y, 37, 37]
      inputs.mouse.down && inputs.mouse.point.inside_rect?(circle_rect)
    end
  
    # Signal that the user is going to be moving the star
    def star_clicked?
      inputs.mouse.down && inputs.mouse.point.inside_rect?(scale_up(state.star))
    end
  
    # Signal that the user is going to be removing walls
    def wall_clicked?
      inputs.mouse.down && mouse_inside_a_wall?
    end
  
    # Signal that the user is going to be adding walls
    def grid_clicked?
      inputs.mouse.down && mouse_inside_grid?
    end
  
    # Returns whether the mouse is inside of a wall
    # Part of the condition that checks whether the user is removing a wall
    def mouse_inside_a_wall?
      state.walls.each_key do | wall |
        return true if inputs.mouse.point.inside_rect?(scale_up([wall.x, wall.y]))
      end
  
      false
    end
  
    # Returns whether the mouse is inside of a grid
    # Part of the condition that checks whether the user is adding a wall
    def mouse_inside_grid?
      inputs.mouse.point.inside_rect?(scale_up([0, 0, grid.width, grid.height]))
    end
  
  
    # These methods provide handy aliases to colors
  
    # Light brown
    def unvisited_color
      [221, 212, 213]
    end
  
    # Black
    def grid_line_color
      [255, 255, 255]
    end
  
    # Dark Brown
    def visited_color
      [204, 191, 179]
    end
  
    # Blue
    def frontier_color
      [103, 136, 204]
    end
  
    # Camo Green
    def wall_color
      [134, 134, 120]
    end
  
    # Button Background
    def gray
      [190, 190, 190]
    end
  
    # Button Outline
    def black
      [0, 0, 0]
    end
  
    # These methods make the code more concise
    def grid
      state.grid
    end
  
    def buttons
      state.buttons
    end
  
    def slider
      state.slider
    end
  end
  
  # Method that is called by DragonRuby periodically
  # Used for updating animations and calculations
  def tick args
  
    # Pressing r will reset the application
    if args.inputs.keyboard.key_down.r
      args.gtk.reset
      reset
      return
    end
  
    # Every tick, new args are passed, and the Breadth First Search tick is called
    $breadth_first_search ||= BreadthFirstSearch.new(args)
    $breadth_first_search.args = args
    $breadth_first_search.tick
  end
  
  
  def reset
    $breadth_first_search = nil
  end

#+end_src

*** Path Finding Algorithms - Detailed Breadth First Search - main.rb
#+begin_src ruby
  # ./samples/13_path_finding_algorithms/02_detailed_breadth_first_search/app/main.rb
  # A visual demonstration of a breadth first search
  # Inspired by https://www.redblobgames.com/pathfinding/a-star/introduction.html
  
  # An animation that can respond to user input in real time
  
  # A breadth first search expands in all directions one step at a time
  # The frontier is a queue of cells to be expanded from
  # The visited hash allows quick lookups of cells that have been expanded from
  # The walls hash allows quick lookup of whether a cell is a wall
  
  # The breadth first search starts by adding the red star to the frontier array
  # and marking it as visited
  # Each step a cell is removed from the front of the frontier array (queue)
  # Unless the neighbor is a wall or visited, it is added to the frontier array
  # The neighbor is then marked as visited
  
  # The frontier is blue
  # Visited cells are light brown
  # Walls are camo green
  # Even when walls are visited, they will maintain their wall color
  
  # This search numbers the order in which new cells are explored
  # The next cell from where the search will continue is highlighted yellow
  # And the cells that will be considered for expansion are in semi-transparent green
  
  # The star can be moved by clicking and dragging
  # Walls can be added and removed by clicking and dragging
  
  class DetailedBreadthFirstSearch
    attr_gtk
  
    def initialize(args)
      # Variables to edit the size and appearance of the grid
      # Freely customizable to user's liking
      args.state.grid.width     = 9
      args.state.grid.height    = 4
      args.state.grid.cell_size = 90
  
      # Stores which step of the animation is being rendered
      # When the user moves the star or messes with the walls,
      # the breadth first search is recalculated up to this step
      args.state.anim_steps = 0 
  
      # At some step the animation will end,
      # and further steps won't change anything (the whole grid will be explored)
      # This step is roughly the grid's width * height
      # When anim_steps equals max_steps no more calculations will occur
      # and the slider will be at the end
      args.state.max_steps  = args.state.grid.width * args.state.grid.height 
  
      # The location of the star and walls of the grid
      # They can be modified to have a different initial grid
      # Walls are stored in a hash for quick look up when doing the search
      args.state.star       = [3, 2]
      args.state.walls      = {}    
  
      # Variables that are used by the breadth first search
      # Storing cells that the search has visited, prevents unnecessary steps
      # Expanding the frontier of the search in order makes the search expand
      # from the center outward
      args.state.visited    = {}
      args.state.frontier   = []
      args.state.cell_numbers = []
  
  
  
      # What the user is currently editing on the grid
      # Possible values are: :none, :slider, :star, :remove_wall, :add_wall
  
      # We store this value, because we want to remember the value even when
      # the user's cursor is no longer over what they're interacting with, but
      # they are still clicking down on the mouse.
      args.state.click_and_drag = :none 
  
      # The x, y, w, h values for the buttons
      # Allow easy movement of the buttons location
      # A centralized location to get values to detect input and draw the buttons
      # Editing these values might mean needing to edit the label offsets
      # which can be found in the appropriate render button methods
      args.state.buttons.left  = [450, 600, 160, 50]
      args.state.buttons.right = [610, 600, 160, 50]
  
      # The variables below are related to the slider
      # They allow the user to customize them
      # They also give a central location for the render and input methods to get
      # information from
      # x & y are the coordinates of the leftmost part of the slider line
      args.state.slider.x = 400
      args.state.slider.y = 675
      # This is the width of the line
      args.state.slider.w = 360
      # This is the offset for the circle
      # Allows the center of the circle to be on the line,
      # as opposed to the upper right corner
      args.state.slider.offset = 20
      # This is the spacing between each of the notches on the slider
      # Notches are places where the circle can rest on the slider line
      # There needs to be a notch for each step before the maximum number of steps
      args.state.slider.spacing = args.state.slider.w.to_f / args.state.max_steps.to_f
    end
  
    # This method is called every frame/tick
    # Every tick, the current state of the search is rendered on the screen,
    # User input is processed, and
    def tick
      render 
      input  
    end
  
    # This method is called from tick and renders everything every tick
    def render
      render_buttons
      render_slider
  
      render_background       
      render_visited 
      render_frontier
      render_walls
      render_star
  
      render_highlights
      render_cell_numbers
    end
  
    # The methods below subdivide the task of drawing everything to the screen
  
    # Draws the buttons that move the search backward or forward
    # These buttons are rendered so the user knows where to click to move the search
    def render_buttons
      render_left_button
      render_right_button
    end
  
    # Renders the button which steps the search backward
    # Shows the user where to click to move the search backward
    def render_left_button
      # Draws the gray button, and a black border
      # The border separates the buttons visually
      outputs.solids  << [buttons.left, gray]
      outputs.borders << [buttons.left, black]
  
      # Renders an explanatory label in the center of the button
      # Explains to the user what the button does
      label_x = buttons.left.x + 05
      label_y = buttons.left.y + 35
      outputs.labels  << [label_x, label_y, "< Step backward"]
    end
  
    # Renders the button which steps the search forward
    # Shows the user where to click to move the search forward
    def render_right_button
      # Draws the gray button, and a black border
      # The border separates the buttons visually
      outputs.solids  << [buttons.right, gray]
      outputs.borders << [buttons.right, black]
  
      # Renders an explanatory label in the center of the button
      # Explains to the user what the button does
      label_x = buttons.right.x + 10
      label_y = buttons.right.y + 35
      outputs.labels  << [label_x, label_y, "Step forward >"]
    end
  
    # Draws the slider so the user can move it and see the progress of the search
    def render_slider
      # Using primitives hides the line under the white circle of the slider
      # Draws the line
      outputs.primitives << [slider.x, slider.y, slider.x + slider.w, slider.y].line
      # The circle needs to be offset so that the center of the circle
      # overlaps the line instead of the upper right corner of the circle
      # The circle's x value is also moved based on the current seach step
      circle_x = (slider.x - slider.offset) + (state.anim_steps * slider.spacing)
      circle_y = (slider.y - slider.offset)
      circle_rect = [circle_x, circle_y, 37, 37]
      outputs.primitives << [circle_rect, 'circle-white.png'].sprite
    end
  
    # Draws what the grid looks like with nothing on it
    # Which is a bunch of unvisited cells
    # Drawn first so other things can draw on top of it
    def render_background
      render_unvisited  
  
      # The grid lines make the cells appear separate
      render_grid_lines 
    end
  
    # Draws a rectangle the size of the entire grid to represent unvisited cells
    # Unvisited cells are the default cell
    def render_unvisited
      background = [0, 0, grid.width, grid.height]
      outputs.solids << [scale_up(background), unvisited_color]
    end
  
    # Draws grid lines to show the division of the grid into cells
    def render_grid_lines
      for x in 0..grid.width
        outputs.lines << [scale_up(vertical_line(x)), grid_line_color]
      end
  
      for y in 0..grid.height
        outputs.lines << [scale_up(horizontal_line(y)), grid_line_color]
      end
    end
  
    # Easy way to get a vertical line given an index
    def vertical_line column
      [column, 0, column, grid.height] 
    end
  
    # Easy way to get a horizontal line given an index
    def horizontal_line row
      [0, row, grid.width, row]
    end
  
    # Draws the area that is going to be searched from
    # The frontier is the most outward parts of the search
    def render_frontier
      state.frontier.each do |cell| 
        outputs.solids << [scale_up(cell), frontier_color]
      end
    end
  
    # Draws the walls
    def render_walls
      state.walls.each_key do |wall|
        outputs.solids << [scale_up(wall), wall_color]
      end
    end
  
    # Renders cells that have been searched in the appropriate color
    def render_visited
      state.visited.each_key do |cell| 
        outputs.solids << [scale_up(cell), visited_color]
      end
    end
  
    # Renders the star
    def render_star
      outputs.sprites << [scale_up(state.star), 'star.png']
    end 
  
    # Cells have a number rendered in them based on when they were explored
    # This is based off of their index in the cell_numbers array
    # Cells are added to this array the same time they are added to the frontier array
    def render_cell_numbers
      state.cell_numbers.each_with_index do |cell, index|
        # Math that approx centers the number in the cell
        label_x = (cell.x * grid.cell_size) + grid.cell_size / 2 - 5
        label_y = (cell.y * grid.cell_size) + (grid.cell_size / 2) + 5
  
        outputs.labels << [label_x, label_y, (index + 1).to_s]
      end
    end
  
    # The next frontier to be expanded is highlighted yellow
    # Its adjacent non-wall neighbors have their border highlighted green
    # This is to show the user how the search expands
    def render_highlights
      return if state.frontier.empty?
  
      # Highlight the next frontier to be expanded yellow
      next_frontier = state.frontier[0]
      outputs.solids << [scale_up(next_frontier), highlighter_yellow]
  
      # Neighbors have a semi-transparent green layer over them
      # Unless the neighbor is a wall
      adjacent_neighbors(next_frontier).each do |neighbor|
        unless state.walls.has_key?(neighbor)
          outputs.solids << [scale_up(neighbor), highlighter_green, 70]
        end
      end
    end
  
  
    # Cell Size is used when rendering to allow the grid to be scaled up or down
    # Cells in the frontier array and visited hash and walls hash are stored as x & y
    # Scaling up cells and lines when rendering allows omitting of width and height
    def scale_up(cell)
      # Prevents the original value of cell from being edited
      cell = cell.clone
  
      # If cell is just an x and y coordinate
      if cell.size == 2
        # Add a width and height of 1
        cell << 1
        cell << 1
      end
  
      # Scale all the values up
      cell.map! { |value| value * grid.cell_size }
  
      # Returns the scaled up cell
      cell
    end
  
  
    # This method processes user input every tick
    # This method allows the user to use the buttons, slider, and edit the grid
    # There are 2 types of input:
    #   Button Input
    #   Click and Drag Input
    #
    #   Button Input is used for the backward step and forward step buttons
    #   Input is detected by mouse up within the bounds of the rect
    #
    #   Click and Drag Input is used for moving the star, adding walls,
    #   removing walls, and the slider
    #
    #   When the mouse is down on the star, the click_and_drag variable is set to :star
    #   While click_and_drag equals :star, the cursor's position is used to calculate the
    #   appropriate drag behavior
    #
    #   When the mouse goes up click_and_drag is set to :none
    #
    #   A variable has to be used because the star has to continue being edited even
    #   when the cursor is no longer over the star
    #
    #   Similar things occur for the other Click and Drag inputs
    def input
      # Processes inputs for the buttons
      input_buttons
  
      # Detects which if any click and drag input is occurring
      detect_click_and_drag          
  
      # Does the appropriate click and drag input based on the click_and_drag variable
      process_click_and_drag         
    end
  
    # Detects and Process input for each button
    def input_buttons
      input_left_button 
      input_right_button     
    end
  
    # Checks if the previous step button is clicked
    # If it is, it pauses the animation and moves the search one step backward
    def input_left_button 
      if left_button_clicked?
        unless state.anim_steps == 0
          state.anim_steps -= 1
          recalculate
        end
      end
    end
  
    # Checks if the next step button is clicked
    # If it is, it pauses the animation and moves the search one step forward
    def input_right_button
      if right_button_clicked?
        unless state.anim_steps == state.max_steps
          state.anim_steps += 1           
          # Although normally recalculate would be called here
          # because the right button only moves the search forward
          # We can just do that
          calc
        end
      end
    end
  
    # Whenever the user edits the grid,
    # The search has to be recalculated upto the current step
  
    def recalculate
      # Resets the search
      state.frontier = [] 
      state.visited = {} 
      state.cell_numbers = []
  
      # Moves the animation forward one step at a time
      state.anim_steps.times { calc } 
    end
  
  
    # Determines what the user is clicking and planning on dragging
    # Click and drag input is initiated by a click on the appropriate item
    # and ended by mouse up
    # Storing the value allows the user to continue the same edit as long as the
    # mouse left click is held
    def detect_click_and_drag
      if inputs.mouse.up                  
        state.click_and_drag = :none          
      elsif star_clicked?                 
        state.click_and_drag = :star          
      elsif wall_clicked?                 
        state.click_and_drag = :remove_wall   
      elsif grid_clicked?                 
        state.click_and_drag = :add_wall      
      elsif slider_clicked?               
        state.click_and_drag = :slider        
      end
    end
  
    # Processes input based on what the user is currently dragging
    def process_click_and_drag
      if state.click_and_drag == :slider          
        input_slider                          
      elsif state.click_and_drag == :star         
        input_star                            
      elsif state.click_and_drag == :remove_wall  
        input_remove_wall                     
      elsif state.click_and_drag == :add_wall     
        input_add_wall                        
      end
    end
  
    # This method is called when the user is dragging the slider
    # It moves the current animation step to the point represented by the slider
    def input_slider
      mouse_x = inputs.mouse.point.x
  
      # Bounds the mouse_x to the closest x value on the slider line
      mouse_x = slider.x if mouse_x < slider.x 
      mouse_x = slider.x + slider.w if mouse_x > slider.x + slider.w 
  
      # Sets the current search step to the one represented by the mouse x value
      # The slider's circle moves due to the render_slider method using anim_steps
      state.anim_steps = ((mouse_x - slider.x) / slider.spacing).to_i
  
      recalculate 
    end
  
    # Moves the star to the grid closest to the mouse
    # Only recalculates the search if the star changes position
    # Called whenever the user is dragging the star 
    def input_star
      old_star = state.star.clone 
      state.star = cell_closest_to_mouse 
      unless old_star == state.star 
        recalculate 
      end
    end
  
    # Removes walls that are under the cursor
    def input_remove_wall
      # The mouse needs to be inside the grid, because we only want to remove walls
      # the cursor is directly over
      # Recalculations should only occur when a wall is actually deleted
      if mouse_inside_grid? 
        if state.walls.has_key?(cell_closest_to_mouse)
          state.walls.delete(cell_closest_to_mouse) 
          recalculate 
        end
      end
    end
  
    # Adds walls at cells under the cursor
    def input_add_wall
      # Adds a wall to the hash
      # We can use the grid closest to mouse, because the cursor is inside the grid
      if mouse_inside_grid? 
        unless state.walls.has_key?(cell_closest_to_mouse)
          state.walls[cell_closest_to_mouse] = true 
          recalculate 
        end
      end
    end
  
    # This method moves the search forward one step
    # When the animation is playing it is called every tick
    # And called whenever the current step of the animation needs to be recalculated
  
    # Moves the search forward one step
    # Parameter called_from_tick is true if it is called from the tick method
    # It is false when the search is being recalculated after user editing the grid
    def calc
      # The setup to the search
      # Runs once when the there is no frontier or visited cells
      if state.frontier.empty? && state.visited.empty?  
        state.frontier << state.star                   
        state.visited[state.star] = true              
      end
  
      # A step in the search
      unless state.frontier.empty? 
        # Takes the next frontier cell
        new_frontier = state.frontier.shift 
        # For each of its neighbors
        adjacent_neighbors(new_frontier).each do |neighbor| 
          # That have not been visited and are not walls
          unless state.visited.has_key?(neighbor) || state.walls.has_key?(neighbor) 
            # Add them to the frontier and mark them as visited
            state.frontier << neighbor 
            state.visited[neighbor] = true 
  
            # Also assign them a frontier number
            state.cell_numbers << neighbor
          end
        end
      end
    end
    
  
    # Returns a list of adjacent cells
    # Used to determine what the next cells to be added to the frontier are
    def adjacent_neighbors cell
      neighbors = [] 
  
      neighbors << [cell.x, cell.y + 1] unless cell.y == grid.height - 1 
      neighbors << [cell.x + 1, cell.y] unless cell.x == grid.width - 1 
      neighbors << [cell.x, cell.y - 1] unless cell.y == 0 
      neighbors << [cell.x - 1, cell.y] unless cell.x == 0 
  
      neighbors 
    end
  
    # When the user grabs the star and puts their cursor to the far right
    # and moves up and down, the star is supposed to move along the grid as well
    # Finding the grid closest to the mouse helps with this
    def cell_closest_to_mouse
      x = (inputs.mouse.point.x / grid.cell_size).to_i 
      y = (inputs.mouse.point.y / grid.cell_size).to_i 
      x = grid.width - 1 if x > grid.width - 1 
      y = grid.height - 1 if y > grid.height - 1 
      [x, y] 
    end
  
  
    # These methods detect when the buttons are clicked
    def left_button_clicked?
      (inputs.mouse.up && inputs.mouse.point.inside_rect?(buttons.left)) || inputs.keyboard.key_up.left
    end
  
    def right_button_clicked?
      (inputs.mouse.up && inputs.mouse.point.inside_rect?(buttons.right)) || inputs.keyboard.key_up.right
    end
  
    # Signal that the user is going to be moving the slider
    def slider_clicked?
      circle_x = (slider.x - slider.offset) + (state.anim_steps * slider.spacing)
      circle_y = (slider.y - slider.offset)
      circle_rect = [circle_x, circle_y, 37, 37]
      inputs.mouse.down && inputs.mouse.point.inside_rect?(circle_rect)
    end
  
    # Signal that the user is going to be moving the star
    def star_clicked?
      inputs.mouse.down && inputs.mouse.point.inside_rect?(scale_up(state.star))
    end
  
    # Signal that the user is going to be removing walls
    def wall_clicked?
      inputs.mouse.down && mouse_inside_a_wall?
    end
  
    # Signal that the user is going to be adding walls
    def grid_clicked?
      inputs.mouse.down && mouse_inside_grid?
    end
  
    # Returns whether the mouse is inside of a wall
    # Part of the condition that checks whether the user is removing a wall
    def mouse_inside_a_wall?
      state.walls.each_key do | wall |
        return true if inputs.mouse.point.inside_rect?(scale_up(wall))
      end
  
      false
    end
  
    # Returns whether the mouse is inside of a grid
    # Part of the condition that checks whether the user is adding a wall
    def mouse_inside_grid?
      inputs.mouse.point.inside_rect?(scale_up([0, 0, grid.width, grid.height]))
    end
  
    # These methods provide handy aliases to colors
  
    # Light brown
    def unvisited_color
      [221, 212, 213] 
    end
  
    # Black
    def grid_line_color
      [255, 255, 255] 
    end
  
    # Dark Brown
    def visited_color
      [204, 191, 179] 
    end
  
    # Blue
    def frontier_color
      [103, 136, 204] 
    end
  
    # Camo Green
    def wall_color
      [134, 134, 120] 
    end
  
    # Next frontier to be expanded
    def highlighter_yellow
      [214, 231, 125]
    end
  
    # The neighbors of the next frontier to be expanded
    def highlighter_green
      [65, 191, 127]
    end
  
    # Button background
    def gray
      [190, 190, 190]
    end
  
    # Button outline
    def black
      [0, 0, 0]
    end
  
    # These methods make the code more concise
    def grid
      state.grid
    end
  
    def buttons
      state.buttons
    end
  
    def slider
      state.slider
    end
  end
  
  
  def tick args
    # Pressing r resets the program
    if args.inputs.keyboard.key_down.r
      args.gtk.reset
      reset
      return
    end
  
    $detailed_breadth_first_search ||= DetailedBreadthFirstSearch.new(args)
    $detailed_breadth_first_search.args = args
    $detailed_breadth_first_search.tick
  end
  
  
  def reset
    $detailed_breadth_first_search = nil
  end

#+end_src

*** Path Finding Algorithms - Breadcrumbs - main.rb
#+begin_src ruby
  # ./samples/13_path_finding_algorithms/03_breadcrumbs/app/main.rb
  class Breadcrumbs
    attr_gtk
  
    # This method is called every frame/tick
    # Every tick, the current state of the search is rendered on the screen,
    # User input is processed, and
    # The next step in the search is calculated
    def tick
      defaults
      # If the grid has not been searched
      if search.came_from.empty?
        calc
        # Calc Path
      end
      render
      input
    end
  
    def defaults
      # Variables to edit the size and appearance of the grid
      # Freely customizable to user's liking
      grid.width     ||= 30
      grid.height    ||= 15
      grid.cell_size ||= 40
      grid.rect      ||= [0, 0, grid.width, grid.height]
  
      # The location of the star and walls of the grid
      # They can be modified to have a different initial grid
      # Walls are stored in a hash for quick look up when doing the search
      grid.star   ||= [2, 8]
      grid.target ||= [10, 5]
      grid.walls  ||= {
        [3, 3] => true,
        [3, 4] => true,
        [3, 5] => true,
        [3, 6] => true,
        [3, 7] => true,
        [3, 8] => true,
        [3, 9] => true,
        [3, 10] => true,
        [3, 11] => true,
        [4, 3] => true,
        [4, 4] => true,
        [4, 5] => true,
        [4, 6] => true,
        [4, 7] => true,
        [4, 8] => true,
        [4, 9] => true,
        [4, 10] => true,
        [4, 11] => true,
        [13, 0] => true,
        [13, 1] => true,
        [13, 2] => true,
        [13, 3] => true,
        [13, 4] => true,
        [13, 5] => true,
        [13, 6] => true,
        [13, 7] => true,
        [13, 8] => true,
        [13, 9] => true,
        [13, 10] => true,
        [14, 0] => true,
        [14, 1] => true,
        [14, 2] => true,
        [14, 3] => true,
        [14, 4] => true,
        [14, 5] => true,
        [14, 6] => true,
        [14, 7] => true,
        [14, 8] => true,
        [14, 9] => true,
        [14, 10] => true,
        [21, 8] => true,
        [21, 9] => true,
        [21, 10] => true,
        [21, 11] => true,
        [21, 12] => true,
        [21, 13] => true,
        [21, 14] => true,
        [22, 8] => true,
        [22, 9] => true,
        [22, 10] => true,
        [22, 11] => true,
        [22, 12] => true,
        [22, 13] => true,
        [22, 14] => true,
        [23, 8] => true,
        [23, 9] => true,
        [24, 8] => true,
        [24, 9] => true,
        [25, 8] => true,
        [25, 9] => true,
      }
  
      # Variables that are used by the breadth first search
      # Storing cells that the search has visited, prevents unnecessary steps
      # Expanding the frontier of the search in order makes the search expand
      # from the center outward
  
      # The cells from which the search is to expand
      search.frontier              ||= []
      # A hash of where each cell was expanded from
      # The key is a cell, and the value is the cell it came from
      search.came_from             ||= {}
      # Cells that are part of the path from the target to the star
      search.path                  ||= {}
  
      # What the user is currently editing on the grid
      # We store this value, because we want to remember the value even when
      # the user's cursor is no longer over what they're interacting with, but
      # they are still clicking down on the mouse.
      state.current_input ||= :none
    end
  
    def calc
      # Setup the search to start from the star
      search.frontier << grid.star
      search.came_from[grid.star] = nil
  
      # Until there are no more cells to expand from
      until search.frontier.empty?
        # Takes the next frontier cell
        new_frontier = search.frontier.shift
        # For each of its neighbors
        adjacent_neighbors(new_frontier).each do |neighbor|
          # That have not been visited and are not walls
          unless search.came_from.has_key?(neighbor) || grid.walls.has_key?(neighbor)
            # Add them to the frontier and mark them as visited in the first grid
            # Unless the target has been visited
            # Add the neighbor to the frontier and remember which cell it came from
            search.frontier << neighbor
            search.came_from[neighbor] = new_frontier
          end
        end
      end
    end
  
  
    # Draws everything onto the screen
    def render
      render_background
      # render_heat_map
      render_walls
      # render_path
      # render_labels
      render_arrows
      render_star
      render_target
      unless grid.walls.has_key?(grid.target)
        render_trail
      end
    end
  
    def render_trail(current_cell=grid.target)
      return if current_cell == grid.star
      parent_cell = search.came_from[current_cell]
      if current_cell && parent_cell
        outputs.lines << [(current_cell.x + 0.5) * grid.cell_size, (current_cell.y + 0.5) * grid.cell_size,
        (parent_cell.x + 0.5) * grid.cell_size, (parent_cell.y + 0.5) * grid.cell_size, purple]
  
      end
      render_trail(parent_cell)
    end
  
    def render_arrows
      search.came_from.each do |child, parent|
        if parent && child
          arrow_cell = [(child.x + parent.x) / 2, (child.y + parent.y) / 2]
          if parent.x > child.x # If the parent cell is to the right of the child cell
            outputs.sprites << [scale_up(arrow_cell), 'arrow.png', 0] # Point the arrow to the right
          elsif parent.x < child.x # If the parent cell is to the right of the child cell
            outputs.sprites << [scale_up(arrow_cell), 'arrow.png', 180] # Point the arrow to the right
          elsif parent.y > child.y # If the parent cell is to the right of the child cell
            outputs.sprites << [scale_up(arrow_cell), 'arrow.png', 90] # Point the arrow to the right
          elsif parent.y < child.y # If the parent cell is to the right of the child cell
            outputs.sprites << [scale_up(arrow_cell), 'arrow.png', 270] # Point the arrow to the right
          end
        end
      end
    end
  
    # The methods below subdivide the task of drawing everything to the screen
  
    # Draws what the grid looks like with nothing on it
    def render_background
      render_unvisited
      render_grid_lines
    end
  
    # Draws both grids
    def render_unvisited
      outputs.solids << [scale_up(grid.rect), unvisited_color]
    end
  
    # Draws grid lines to show the division of the grid into cells
    def render_grid_lines
      for x in 0..grid.width
        outputs.lines << vertical_line(x)
      end
  
      for y in 0..grid.height
        outputs.lines << horizontal_line(y)
      end
    end
  
    # Easy way to draw vertical lines given an index
    def vertical_line column
      scale_up([column, 0, column, grid.height])
    end
  
    # Easy way to draw horizontal lines given an index
    def horizontal_line row
      scale_up([0, row, grid.width, row])
    end
  
    # Draws the walls on both grids
    def render_walls
      grid.walls.each_key do |wall|
        outputs.solids << [scale_up(wall), wall_color]
      end
    end
  
    # Renders the star on both grids
    def render_star
      outputs.sprites << [scale_up(grid.star), 'star.png']
    end
  
    # Renders the target on both grids
    def render_target
      outputs.sprites << [scale_up(grid.target), 'target.png']
    end
  
    # Labels the grids
    def render_labels
      outputs.labels << [200, 625, "Without early exit"]
    end
  
    # Renders the path based off of the search.path hash
    def render_path
      # If the star and target are disconnected there will only be one path
      # The path should not render in that case
      unless search.path.size == 1
        search.path.each_key do | cell |
          # Renders path on both grids
          outputs.solids << [scale_up(cell), path_color]
        end
      end
    end
  
    # Calculates the path from the target to the star after the search is over
    # Relies on the came_from hash
    # Fills the search.path hash, which is later rendered on screen
    def calc_path
      endpoint = grid.target
      while endpoint
        search.path[endpoint] = true
        endpoint = search.came_from[endpoint]
      end
    end
  
    # In code, the cells are represented as 1x1 rectangles
    # When drawn, the cells are larger than 1x1 rectangles
    # This method is used to scale up cells, and lines
    # Objects are scaled up according to the grid.cell_size variable
    # This allows for easy customization of the visual scale of the grid
    def scale_up(cell)
      # Prevents the original value of cell from being edited
      cell = cell.clone
  
      # If cell is just an x and y coordinate
      if cell.size == 2
        # Add a width and height of 1
        cell << 1
        cell << 1
      end
  
      # Scale all the values up
      cell.map! { |value| value * grid.cell_size }
  
      # Returns the scaled up cell
      cell
    end
  
    # This method processes user input every tick
    # Any method with "1" is related to the first grid
    # Any method with "2" is related to the second grid
    def input
      # The program has to remember that the user is dragging an object
      # even when the mouse is no longer over that object
      # So detecting input and processing input is separate
      # detect_input
      # process_input
      if inputs.mouse.up
        state.current_input = :none
      elsif star_clicked?
        state.current_input = :star
      end
  
      if mouse_inside_grid?
        unless grid.target == cell_closest_to_mouse
          grid.target = cell_closest_to_mouse
        end
        if state.current_input == :star
          unless grid.star == cell_closest_to_mouse
            grid.star = cell_closest_to_mouse
          end
        end
      end
    end
  
    # Determines what the user is editing and stores the value
    # Storing the value allows the user to continue the same edit as long as the
    # mouse left click is held
    def detect_input
      # When the mouse is up, nothing is being edited
      if inputs.mouse.up
        state.current_input = :none
      # When the star in the no second grid is clicked
      elsif star_clicked?
        state.current_input = :star
      # When the target in the no second grid is clicked
      elsif target_clicked?
        state.current_input = :target
      # When a wall in the first grid is clicked
      elsif wall_clicked?
        state.current_input = :remove_wall
      # When the first grid is clicked
      elsif grid_clicked?
        state.current_input = :add_wall
      end
    end
  
    # Processes click and drag based on what the user is currently dragging
    def process_input
      if state.current_input == :star
        input_star
      elsif state.current_input == :target
        input_target
      elsif state.current_input == :remove_wall
        input_remove_wall
      elsif state.current_input == :add_wall
        input_add_wall
      end
    end
  
    # Moves the star to the cell closest to the mouse in the first grid
    # Only resets the search if the star changes position
    # Called whenever the user is editing the star (puts mouse down on star)
    def input_star
      old_star = grid.star.clone
      grid.star = cell_closest_to_mouse
      unless old_star == grid.star
        reset_search
      end
    end
  
    # Moves the target to the grid closest to the mouse in the first grid
    # Only reset_searchs the search if the target changes position
    # Called whenever the user is editing the target (puts mouse down on target)
    def input_target
      old_target = grid.target.clone
      grid.target = cell_closest_to_mouse
      unless old_target == grid.target
        reset_search
      end
    end
  
    # Removes walls in the first grid that are under the cursor
    def input_remove_wall
      # The mouse needs to be inside the grid, because we only want to remove walls
      # the cursor is directly over
      # Recalculations should only occur when a wall is actually deleted
      if mouse_inside_grid?
        if grid.walls.has_key?(cell_closest_to_mouse)
          grid.walls.delete(cell_closest_to_mouse)
          reset_search
        end
      end
    end
  
    # Adds a wall in the first grid in the cell the mouse is over
    def input_add_wall
      if mouse_inside_grid?
        unless grid.walls.has_key?(cell_closest_to_mouse)
          grid.walls[cell_closest_to_mouse] = true
          reset_search
        end
      end
    end
  
  
    # Whenever the user edits the grid,
    # The search has to be reset_searchd upto the current step
    # with the current grid as the initial state of the grid
    def reset_search
      # Reset_Searchs the search
      search.frontier  = []
      search.came_from = {}
      search.path      = {}
    end
  
  
    # Returns a list of adjacent cells
    # Used to determine what the next cells to be added to the frontier are
    def adjacent_neighbors(cell)
      neighbors = []
  
      # Gets all the valid neighbors into the array
      # From southern neighbor, clockwise
      neighbors << [cell.x, cell.y - 1] unless cell.y == 0
      neighbors << [cell.x - 1, cell.y] unless cell.x == 0
      neighbors << [cell.x, cell.y + 1] unless cell.y == grid.height - 1
      neighbors << [cell.x + 1, cell.y] unless cell.x == grid.width - 1
  
      # Sorts the neighbors so the rendered path is a zigzag path
      # Cells in a diagonal direction are given priority
      # Comment this line to see the difference
      neighbors = neighbors.sort_by { |neighbor_x, neighbor_y|  proximity_to_star(neighbor_x, neighbor_y) }
  
      neighbors
    end
  
    # Finds the vertical and horizontal distance of a cell from the star
    # and returns the larger value
    # This method is used to have a zigzag pattern in the rendered path
    # A cell that is [5, 5] from the star,
    # is explored before over a cell that is [0, 7] away.
    # So, if possible, the search tries to go diagonal (zigzag) first
    def proximity_to_star(x, y)
      distance_x = (grid.star.x - x).abs
      distance_y = (grid.star.y - y).abs
  
      if distance_x > distance_y
        return distance_x
      else
        return distance_y
      end
    end
  
    # When the user grabs the star and puts their cursor to the far right
    # and moves up and down, the star is supposed to move along the grid as well
    # Finding the cell closest to the mouse helps with this
    def cell_closest_to_mouse
      # Closest cell to the mouse in the first grid
      x = (inputs.mouse.point.x / grid.cell_size).to_i
      y = (inputs.mouse.point.y / grid.cell_size).to_i
      # Bound x and y to the grid
      x = grid.width - 1 if x > grid.width - 1
      y = grid.height - 1 if y > grid.height - 1
      # Return closest cell
      [x, y]
    end
  
    # Signal that the user is going to be moving the star from the first grid
    def star_clicked?
      inputs.mouse.down && inputs.mouse.point.inside_rect?(scale_up(grid.star))
    end
  
    # Signal that the user is going to be moving the target from the first grid
    def target_clicked?
      inputs.mouse.down && inputs.mouse.point.inside_rect?(scale_up(grid.target))
    end
  
    # Signal that the user is going to be adding walls from the first grid
    def grid_clicked?
      inputs.mouse.down && mouse_inside_grid?
    end
  
    # Returns whether the mouse is inside of the first grid
    # Part of the condition that checks whether the user is adding a wall
    def mouse_inside_grid?
      inputs.mouse.point.inside_rect?(scale_up(grid.rect))
    end
  
    # These methods provide handy aliases to colors
  
    # Light brown
    def unvisited_color
      [221, 212, 213]
      # [255, 255, 255]
    end
  
    # Camo Green
    def wall_color
      [134, 134, 120]
    end
  
    # Pastel White
    def path_color
      [231, 230, 228]
    end
  
    def red
      [255, 0, 0]
    end
  
    def purple
      [149, 64, 191]
    end
  
    # Makes code more concise
    def grid
      state.grid
    end
  
    def search
      state.search
    end
  end
  
  # Method that is called by DragonRuby periodically
  # Used for updating animations and calculations
  def tick args
  
    # Pressing r will reset the application
    if args.inputs.keyboard.key_down.r
      args.gtk.reset
      reset
      return
    end
  
    # Every tick, new args are passed, and the Breadth First Search tick is called
    $breadcrumbs ||= Breadcrumbs.new
    $breadcrumbs.args = args
    $breadcrumbs.tick
  end
  
  
  def reset
    $breadcrumbs = nil
  end
  
   #  # Representation of how far away visited cells are from the star
   #  # Replaces the render_visited method
   #  # Visually demonstrates the effectiveness of early exit for pathfinding
   #  def render_heat_map
   #    # THIS CODE NEEDS SOME FIXING DUE TO REFACTORING
   #    search.came_from.each_key do | cell |
   #      distance = (grid.star.x - visited_cell.x).abs + (state.star.y - visited_cell.y).abs
   #      max_distance = grid.width + grid.height
   #      alpha = 255.to_i * distance.to_i / max_distance.to_i
   #      outputs.solids << [scale_up(visited_cell), red, alpha]
   #      # outputs.solids << [early_exit_scale_up(visited_cell), red, alpha]
   #    end
   #  end

#+end_src

*** Path Finding Algorithms - Early Exit - main.rb
#+begin_src ruby
  # ./samples/13_path_finding_algorithms/04_early_exit/app/main.rb
  # Comparison of a breadth first search with and without early exit
  # Inspired by https://www.redblobgames.com/pathfinding/a-star/introduction.html
  
  # Demonstrates the exploration difference caused by early exit
  # Also demonstrates how breadth first search is used for path generation
  
  # The left grid is a breadth first search without early exit
  # The right grid is a breadth first search with early exit
  # The red squares represent how far the search expanded
  # The darker the red, the farther the search proceeded
  # Comparison of the heat map reveals how much searching can be saved by early exit
  # The white path shows path generation via breadth first search
  class EarlyExitBreadthFirstSearch
    attr_gtk
  
    # This method is called every frame/tick
    # Every tick, the current state of the search is rendered on the screen,
    # User input is processed, and
    # The next step in the search is calculated
    def tick
      defaults
      # If the grid has not been searched
      if state.visited.empty?
        # Complete the search
        state.max_steps.times { step }
        # And calculate the path
        calc_path
      end
      render
      input
    end
  
    def defaults
      # Variables to edit the size and appearance of the grid
      # Freely customizable to user's liking
      grid.width     ||= 15
      grid.height    ||= 15
      grid.cell_size ||= 40
      grid.rect      ||= [0, 0, grid.width, grid.height]
  
      # At some step the animation will end,
      # and further steps won't change anything (the whole grid.widthill be explored)
      # This step is roughly the grid's width * height
      # When anim_steps equals max_steps no more calculations will occur
      # and the slider will be at the end
      state.max_steps  ||= args.state.grid.width * args.state.grid.height
  
      # The location of the star and walls of the grid
      # They can be modified to have a different initial grid
      # Walls are stored in a hash for quick look up when doing the search
      state.star   ||= [2, 8]
      state.target ||= [10, 5]
      state.walls  ||= {}
  
      # Variables that are used by the breadth first search
      # Storing cells that the search has visited, prevents unnecessary steps
      # Expanding the frontier of the search in order makes the search expand
      # from the center outward
  
      # Visited cells in the first grid
      state.visited               ||= {}
      # Visited cells in the second grid
      state.early_exit_visited    ||= {}
      # The cells from which the search is to expand
      state.frontier              ||= []
      # A hash of where each cell was expanded from
      # The key is a cell, and the value is the cell it came from
      state.came_from             ||= {}
      # Cells that are part of the path from the target to the star
      state.path                  ||= {}
  
      # What the user is currently editing on the grid
      # We store this value, because we want to remember the value even when
      # the user's cursor is no longer over what they're interacting with, but
      # they are still clicking down on the mouse.
      state.current_input ||= :none
    end
  
    # Draws everything onto the screen
    def render
      render_background
      render_heat_map
      render_walls
      render_path
      render_star
      render_target
      render_labels
    end
  
    # The methods below subdivide the task of drawing everything to the screen
  
    # Draws what the grid looks like with nothing on it
    def render_background
      render_unvisited
      render_grid_lines
    end
  
    # Draws both grids
    def render_unvisited
      outputs.solids << [scale_up(grid.rect), unvisited_color]
      outputs.solids << [early_exit_scale_up(grid.rect), unvisited_color]
    end
  
    # Draws grid lines to show the division of the grid into cells
    def render_grid_lines
      for x in 0..grid.width
        outputs.lines << vertical_line(x)
        outputs.lines << early_exit_vertical_line(x)
      end
  
      for y in 0..grid.height
        outputs.lines << horizontal_line(y)
        outputs.lines << early_exit_horizontal_line(y)
      end
    end
  
    # Easy way to draw vertical lines given an index
    def vertical_line column
      scale_up([column, 0, column, grid.height])
    end
  
    # Easy way to draw horizontal lines given an index
    def horizontal_line row
      scale_up([0, row, grid.width, row])
    end
  
    # Easy way to draw vertical lines given an index
    def early_exit_vertical_line column
      scale_up([column + grid.width + 1, 0, column + grid.width + 1, grid.height])
    end
  
    # Easy way to draw horizontal lines given an index
    def early_exit_horizontal_line row
      scale_up([grid.width + 1, row, grid.width + grid.width + 1, row])
    end
  
    # Draws the walls on both grids
    def render_walls
      state.walls.each_key do |wall|
        outputs.solids << [scale_up(wall), wall_color]
        outputs.solids << [early_exit_scale_up(wall), wall_color]
      end
    end
  
    # Renders the star on both grids
    def render_star
      outputs.sprites << [scale_up(state.star), 'star.png']
      outputs.sprites << [early_exit_scale_up(state.star), 'star.png']
    end
  
    # Renders the target on both grids
    def render_target
      outputs.sprites << [scale_up(state.target), 'target.png']
      outputs.sprites << [early_exit_scale_up(state.target), 'target.png']
    end
  
    # Labels the grids
    def render_labels
      outputs.labels << [200, 625, "Without early exit"]
      outputs.labels << [875, 625, "With early exit"]
    end
  
    # Renders the path based off of the state.path hash
    def render_path
      # If the star and target are disconnected there will only be one path
      # The path should not render in that case
      unless state.path.size == 1
        state.path.each_key do | cell |
          # Renders path on both grids
          outputs.solids << [scale_up(cell), path_color]
          outputs.solids << [early_exit_scale_up(cell), path_color]
        end
      end
    end
  
    # Calculates the path from the target to the star after the search is over
    # Relies on the came_from hash
    # Fills the state.path hash, which is later rendered on screen
    def calc_path
      endpoint = state.target
      while endpoint
        state.path[endpoint] = true
        endpoint = state.came_from[endpoint]
      end
    end
  
    # Representation of how far away visited cells are from the star
    # Replaces the render_visited method
    # Visually demonstrates the effectiveness of early exit for pathfinding
    def render_heat_map
      state.visited.each_key do | visited_cell |
        distance = (state.star.x - visited_cell.x).abs + (state.star.y - visited_cell.y).abs
        max_distance = grid.width + grid.height
        alpha = 255.to_i * distance.to_i / max_distance.to_i
        outputs.solids << [scale_up(visited_cell), red, alpha]
        # outputs.solids << [early_exit_scale_up(visited_cell), red, alpha]
      end
  
      state.early_exit_visited.each_key do | visited_cell |
        distance = (state.star.x - visited_cell.x).abs + (state.star.y - visited_cell.y).abs
        max_distance = grid.width + grid.height
        alpha = 255.to_i * distance.to_i / max_distance.to_i
        outputs.solids << [early_exit_scale_up(visited_cell), red, alpha]
      end
    end
  
    # Translates the given cell grid.width + 1 to the right and then scales up
    # Used to draw cells for the second grid
    # This method does not work for lines,
    # so separate methods exist for the grid lines
    def early_exit_scale_up(cell)
      cell_clone = cell.clone
      cell_clone.x += grid.width + 1
      scale_up(cell_clone)
    end
  
    # In code, the cells are represented as 1x1 rectangles
    # When drawn, the cells are larger than 1x1 rectangles
    # This method is used to scale up cells, and lines
    # Objects are scaled up according to the grid.cell_size variable
    # This allows for easy customization of the visual scale of the grid
    def scale_up(cell)
      # Prevents the original value of cell from being edited
      cell = cell.clone
  
      # If cell is just an x and y coordinate
      if cell.size == 2
        # Add a width and height of 1
        cell << 1
        cell << 1
      end
  
      # Scale all the values up
      cell.map! { |value| value * grid.cell_size }
  
      # Returns the scaled up cell
      cell
    end
  
    # This method processes user input every tick
    # Any method with "1" is related to the first grid
    # Any method with "2" is related to the second grid
    def input
      # The program has to remember that the user is dragging an object
      # even when the mouse is no longer over that object
      # So detecting input and processing input is separate
      detect_input
      process_input
    end
  
    # Determines what the user is editing and stores the value
    # Storing the value allows the user to continue the same edit as long as the
    # mouse left click is held
    def detect_input
      # When the mouse is up, nothing is being edited
      if inputs.mouse.up
        state.current_input = :none
      # When the star in the no second grid is clicked
      elsif star_clicked?
        state.current_input = :star
      # When the star in the second grid is clicked
      elsif star2_clicked?
        state.current_input = :star2
      # When the target in the no second grid is clicked
      elsif target_clicked?
        state.current_input = :target
      # When the target in the second grid is clicked
      elsif target2_clicked?
        state.current_input = :target2
      # When a wall in the first grid is clicked
      elsif wall_clicked?
        state.current_input = :remove_wall
      # When a wall in the second grid is clicked
      elsif wall2_clicked?
        state.current_input = :remove_wall2
      # When the first grid is clicked
      elsif grid_clicked?
        state.current_input = :add_wall
      # When the second grid is clicked
      elsif grid2_clicked?
        state.current_input = :add_wall2
      end
    end
  
    # Processes click and drag based on what the user is currently dragging
    def process_input
      if state.current_input == :star
        input_star
      elsif state.current_input == :star2
        input_star2
      elsif state.current_input == :target
        input_target
      elsif state.current_input == :target2
        input_target2
      elsif state.current_input == :remove_wall
        input_remove_wall
      elsif state.current_input == :remove_wall2
        input_remove_wall2
      elsif state.current_input == :add_wall
        input_add_wall
      elsif state.current_input == :add_wall2
        input_add_wall2
      end
    end
  
    # Moves the star to the cell closest to the mouse in the first grid
    # Only resets the search if the star changes position
    # Called whenever the user is editing the star (puts mouse down on star)
    def input_star
      old_star = state.star.clone
      state.star = cell_closest_to_mouse
      unless old_star == state.star
        reset_search
      end
    end
  
    # Moves the star to the cell closest to the mouse in the second grid
    # Only resets the search if the star changes position
    # Called whenever the user is editing the star (puts mouse down on star)
    def input_star2
      old_star = state.star.clone
      state.star = cell_closest_to_mouse2
      unless old_star == state.star
        reset_search
      end
    end
  
    # Moves the target to the grid closest to the mouse in the first grid
    # Only reset_searchs the search if the target changes position
    # Called whenever the user is editing the target (puts mouse down on target)
    def input_target
      old_target = state.target.clone
      state.target = cell_closest_to_mouse
      unless old_target == state.target
        reset_search
      end
    end
  
    # Moves the target to the cell closest to the mouse in the second grid
    # Only reset_searchs the search if the target changes position
    # Called whenever the user is editing the target (puts mouse down on target)
    def input_target2
      old_target = state.target.clone
      state.target = cell_closest_to_mouse2
      unless old_target == state.target
        reset_search
      end
    end
  
    # Removes walls in the first grid that are under the cursor
    def input_remove_wall
      # The mouse needs to be inside the grid, because we only want to remove walls
      # the cursor is directly over
      # Recalculations should only occur when a wall is actually deleted
      if mouse_inside_grid?
        if state.walls.has_key?(cell_closest_to_mouse)
          state.walls.delete(cell_closest_to_mouse)
          reset_search
        end
      end
    end
  
    # Removes walls in the second grid that are under the cursor
    def input_remove_wall2
      # The mouse needs to be inside the grid, because we only want to remove walls
      # the cursor is directly over
      # Recalculations should only occur when a wall is actually deleted
      if mouse_inside_grid2?
        if state.walls.has_key?(cell_closest_to_mouse2)
          state.walls.delete(cell_closest_to_mouse2)
          reset_search
        end
      end
    end
  
    # Adds a wall in the first grid in the cell the mouse is over
    def input_add_wall
      if mouse_inside_grid?
        unless state.walls.has_key?(cell_closest_to_mouse)
          state.walls[cell_closest_to_mouse] = true
          reset_search
        end
      end
    end
  
  
    # Adds a wall in the second grid in the cell the mouse is over
    def input_add_wall2
      if mouse_inside_grid2?
        unless state.walls.has_key?(cell_closest_to_mouse2)
          state.walls[cell_closest_to_mouse2] = true
          reset_search
        end
      end
    end
  
    # Whenever the user edits the grid,
    # The search has to be reset_searchd upto the current step
    # with the current grid as the initial state of the grid
    def reset_search
      # Reset_Searchs the search
      state.frontier  = []
      state.visited   = {}
      state.early_exit_visited   = {}
      state.came_from = {}
      state.path      = {}
    end
  
    # Moves the search forward one step
    def step
      # The setup to the search
      # Runs once when there are no visited cells
      if state.visited.empty?
        state.visited[state.star] = true
        state.early_exit_visited[state.star] = true
        state.frontier << state.star
        state.came_from[state.star] = nil
      end
  
      # A step in the search
      unless state.frontier.empty?
        # Takes the next frontier cell
        new_frontier = state.frontier.shift
        # For each of its neighbors
        adjacent_neighbors(new_frontier).each do |neighbor|
          # That have not been visited and are not walls
          unless state.visited.has_key?(neighbor) || state.walls.has_key?(neighbor)
            # Add them to the frontier and mark them as visited in the first grid
            state.visited[neighbor] = true
            # Unless the target has been visited
            unless state.visited.has_key?(state.target)
              # Mark the neighbor as visited in the second grid as well
              state.early_exit_visited[neighbor] = true
            end
  
            # Add the neighbor to the frontier and remember which cell it came from
            state.frontier << neighbor
            state.came_from[neighbor] = new_frontier
          end
        end
      end
    end
  
  
    # Returns a list of adjacent cells
    # Used to determine what the next cells to be added to the frontier are
    def adjacent_neighbors(cell)
      neighbors = []
  
      # Gets all the valid neighbors into the array
      # From southern neighbor, clockwise
      neighbors << [cell.x, cell.y - 1] unless cell.y == 0
      neighbors << [cell.x - 1, cell.y] unless cell.x == 0
      neighbors << [cell.x, cell.y + 1] unless cell.y == grid.height - 1
      neighbors << [cell.x + 1, cell.y] unless cell.x == grid.width - 1
  
      # Sorts the neighbors so the rendered path is a zigzag path
      # Cells in a diagonal direction are given priority
      # Comment this line to see the difference
      neighbors = neighbors.sort_by { |neighbor_x, neighbor_y|  proximity_to_star(neighbor_x, neighbor_y) }
  
      neighbors
    end
  
    # Finds the vertical and horizontal distance of a cell from the star
    # and returns the larger value
    # This method is used to have a zigzag pattern in the rendered path
    # A cell that is [5, 5] from the star,
    # is explored before over a cell that is [0, 7] away.
    # So, if possible, the search tries to go diagonal (zigzag) first
    def proximity_to_star(x, y)
      distance_x = (state.star.x - x).abs
      distance_y = (state.star.y - y).abs
  
      if distance_x > distance_y
        return distance_x
      else
        return distance_y
      end
    end
  
    # When the user grabs the star and puts their cursor to the far right
    # and moves up and down, the star is supposed to move along the grid as well
    # Finding the cell closest to the mouse helps with this
    def cell_closest_to_mouse
      # Closest cell to the mouse in the first grid
      x = (inputs.mouse.point.x / grid.cell_size).to_i
      y = (inputs.mouse.point.y / grid.cell_size).to_i
      # Bound x and y to the grid
      x = grid.width - 1 if x > grid.width - 1
      y = grid.height - 1 if y > grid.height - 1
      # Return closest cell
      [x, y]
    end
  
    # When the user grabs the star and puts their cursor to the far right
    # and moves up and down, the star is supposed to move along the grid as well
    # Finding the cell closest to the mouse in the second grid helps with this
    def cell_closest_to_mouse2
      # Closest cell grid to the mouse in the second
      x = (inputs.mouse.point.x / grid.cell_size).to_i
      y = (inputs.mouse.point.y / grid.cell_size).to_i
      # Translate the cell to the first grid
      x -= grid.width + 1
      # Bound x and y to the first grid
      x = grid.width - 1 if x > grid.width - 1
      y = grid.height - 1 if y > grid.height - 1
      # Return closest cell
      [x, y]
    end
  
    # Signal that the user is going to be moving the star from the first grid
    def star_clicked?
      inputs.mouse.down && inputs.mouse.point.inside_rect?(scale_up(state.star))
    end
  
    # Signal that the user is going to be moving the star from the second grid
    def star2_clicked?
      inputs.mouse.down && inputs.mouse.point.inside_rect?(early_exit_scale_up(state.star))
    end
  
    # Signal that the user is going to be moving the target from the first grid
    def target_clicked?
      inputs.mouse.down && inputs.mouse.point.inside_rect?(scale_up(state.target))
    end
  
    # Signal that the user is going to be moving the target from the second grid
    def target2_clicked?
      inputs.mouse.down && inputs.mouse.point.inside_rect?(early_exit_scale_up(state.target))
    end
  
    # Signal that the user is going to be removing walls from the first grid
    def wall_clicked?
      inputs.mouse.down && mouse_inside_wall?
    end
  
    # Signal that the user is going to be removing walls from the second grid
    def wall2_clicked?
      inputs.mouse.down && mouse_inside_wall2?
    end
  
    # Signal that the user is going to be adding walls from the first grid
    def grid_clicked?
      inputs.mouse.down && mouse_inside_grid?
    end
  
    # Signal that the user is going to be adding walls from the second grid
    def grid2_clicked?
      inputs.mouse.down && mouse_inside_grid2?
    end
  
    # Returns whether the mouse is inside of a wall in the first grid
    # Part of the condition that checks whether the user is removing a wall
    def mouse_inside_wall?
      state.walls.each_key do | wall |
        return true if inputs.mouse.point.inside_rect?(scale_up(wall))
      end
  
      false
    end
  
    # Returns whether the mouse is inside of a wall in the second grid
    # Part of the condition that checks whether the user is removing a wall
    def mouse_inside_wall2?
      state.walls.each_key do | wall |
        return true if inputs.mouse.point.inside_rect?(early_exit_scale_up(wall))
      end
  
      false
    end
  
    # Returns whether the mouse is inside of the first grid
    # Part of the condition that checks whether the user is adding a wall
    def mouse_inside_grid?
      inputs.mouse.point.inside_rect?(scale_up(grid.rect))
    end
  
    # Returns whether the mouse is inside of the second grid
    # Part of the condition that checks whether the user is adding a wall
    def mouse_inside_grid2?
      inputs.mouse.point.inside_rect?(early_exit_scale_up(grid.rect))
    end
  
    # These methods provide handy aliases to colors
  
    # Light brown
    def unvisited_color
      [221, 212, 213]
    end
  
    # Camo Green
    def wall_color
      [134, 134, 120]
    end
  
    # Pastel White
    def path_color
      [231, 230, 228]
    end
  
    def red
      [255, 0, 0]
    end
  
    # Makes code more concise
    def grid
      state.grid
    end
  end
  
  # Method that is called by DragonRuby periodically
  # Used for updating animations and calculations
  def tick args
  
    # Pressing r will reset the application
    if args.inputs.keyboard.key_down.r
      args.gtk.reset
      reset
      return
    end
  
    # Every tick, new args are passed, and the Breadth First Search tick is called
    $early_exit_breadth_first_search ||= EarlyExitBreadthFirstSearch.new
    $early_exit_breadth_first_search.args = args
    $early_exit_breadth_first_search.tick
  end
  
  
  def reset
    $early_exit_breadth_first_search = nil
  end

#+end_src

*** Path Finding Algorithms - Dijkstra - main.rb
#+begin_src ruby
  # ./samples/13_path_finding_algorithms/05_dijkstra/app/main.rb
  # Demonstrates how Dijkstra's Algorithm allows movement costs to be considered
  
  # Inspired by https://www.redblobgames.com/pathfinding/a-star/introduction.html
  
  # The first grid is a breadth first search with an early exit.
  # It shows a heat map of all the cells that were visited by the search and their relative distance.
  
  # The second grid is an implementation of Dijkstra's algorithm.
  # Light green cells have 5 times the movement cost of regular cells.
  # The heat map will darken based on movement cost.
  
  # Dark green cells are walls, and the search cannot go through them.
  class Movement_Costs
    attr_gtk
  
    # This method is called every frame/tick
    # Every tick, the current state of the search is rendered on the screen,
    # User input is processed, and
    # The next step in the search is calculated
    def tick
      defaults
      render
      input
      calc
    end
  
    def defaults
      # Variables to edit the size and appearance of the grid
      # Freely customizable to user's liking
      grid.width     ||= 10
      grid.height    ||= 10
      grid.cell_size ||= 60
      grid.rect      ||= [0, 0, grid.width, grid.height]
  
      # The location of the star and walls of the grid
      # They can be modified to have a different initial grid
      # Walls are stored in a hash for quick look up when doing the search
      state.star   ||= [1, 5]
      state.target ||= [8, 4]
      state.walls  ||= {[1, 1] => true, [2, 1] => true, [3, 1] => true, [1, 2] => true, [2, 2] => true, [3, 2] => true}
      state.hills  ||= {
        [4, 1] => true,
        [5, 1] => true,
        [4, 2] => true,
        [5, 2] => true,
        [6, 2] => true,
        [4, 3] => true,
        [5, 3] => true,
        [6, 3] => true,
        [3, 4] => true,
        [4, 4] => true,
        [5, 4] => true,
        [6, 4] => true,
        [7, 4] => true,
        [3, 5] => true,
        [4, 5] => true,
        [5, 5] => true,
        [6, 5] => true,
        [7, 5] => true,
        [4, 6] => true,
        [5, 6] => true,
        [6, 6] => true,
        [7, 6] => true,
        [4, 7] => true,
        [5, 7] => true,
        [6, 7] => true,
        [4, 8] => true,
        [5, 8] => true,
      }
  
      # What the user is currently editing on the grid
      # We store this value, because we want to remember the value even when
      # the user's cursor is no longer over what they're interacting with, but
      # they are still clicking down on the mouse.
      state.user_input ||= :none
  
      # Values that are used for the breadth first search
      # Keeping track of what cells were visited prevents counting cells multiple times
      breadth_first_search.visited    ||= {}
      # The cells from which the breadth first search will expand
      breadth_first_search.frontier   ||= []
      # Keeps track of which cell all cells were searched from
      # Used to recreate the path from the target to the star
      breadth_first_search.came_from  ||= {}
  
      # Keeps track of the movement cost so far to be at a cell
      # Allows the costs of new cells to be quickly calculated
      # Also doubles as a way to check if cells have already been visited
      dijkstra_search.cost_so_far ||= {}
      # The cells from which the Dijkstra search will expand
      dijkstra_search.frontier    ||= []
      # Keeps track of which cell all cells were searched from
      # Used to recreate the path from the target to the star
      dijkstra_search.came_from   ||= {}
    end
  
    # Draws everything onto the screen
    def render
      render_background
  
      render_heat_maps
  
      render_star
      render_target
      render_hills
      render_walls
  
      render_paths
    end
    # The methods below subdivide the task of drawing everything to the screen
  
    # Draws what the grid looks like with nothing on it
    def render_background
      render_unvisited
      render_grid_lines
      render_labels
    end
  
    # Draws two rectangles the size of the grid in the default cell color
    # Used as part of the background
    def render_unvisited
      outputs.solids << [scale_up(grid.rect), unvisited_color]
      outputs.solids << [move_and_scale_up(grid.rect), unvisited_color]
    end
  
    # Draws grid lines to show the division of the grid into cells
    def render_grid_lines
      for x in 0..grid.width
        outputs.lines << vertical_line(x)
        outputs.lines << shifted_vertical_line(x)
      end
  
      for y in 0..grid.height
        outputs.lines << horizontal_line(y)
        outputs.lines << shifted_horizontal_line(y)
      end
    end
  
    # Easy way to draw vertical lines given an index for the first grid
    def vertical_line column
      scale_up([column, 0, column, grid.height])
    end
  
    # Easy way to draw horizontal lines given an index for the second grid
    def horizontal_line row
      scale_up([0, row, grid.width, row])
    end
  
    # Easy way to draw vertical lines given an index for the first grid
    def shifted_vertical_line column
      scale_up([column + grid.width + 1, 0, column + grid.width + 1, grid.height])
    end
  
    # Easy way to draw horizontal lines given an index for the second grid
    def shifted_horizontal_line row
      scale_up([grid.width + 1, row, grid.width + grid.width + 1, row])
    end
  
    # Labels the grids
    def render_labels
      outputs.labels << [175, 650, "Number of steps", 3]
      outputs.labels << [925, 650, "Distance", 3]
    end
  
    def render_paths
      render_breadth_first_search_path
      render_dijkstra_path
    end
  
    def render_heat_maps
      render_breadth_first_search_heat_map
      render_dijkstra_heat_map
    end
  
    # Renders the breadth first search on the first grid
    def render_breadth_first_search
    end
  
    # This heat map shows the cells explored by the breadth first search and how far they are from the star.
    def render_breadth_first_search_heat_map
      # For each cell explored
      breadth_first_search.visited.each_key do | visited_cell |
        # Find its distance from the star
        distance = (state.star.x - visited_cell.x).abs + (state.star.y - visited_cell.y).abs
        max_distance = grid.width + grid.height
        # Get it as a percent of the maximum distance and scale to 255 for use as an alpha value
        alpha = 255.to_i * distance.to_i / max_distance.to_i
        outputs.solids << [scale_up(visited_cell), red, alpha]
      end
    end
  
    def render_breadth_first_search_path
      # If the search found the target
      if breadth_first_search.visited.has_key?(state.target)
        # Start from the target
        endpoint = state.target
        # And the cell it came from
        next_endpoint = breadth_first_search.came_from[endpoint]
        while endpoint and next_endpoint
          # Draw a path between these two cells
          path = get_path_between(endpoint, next_endpoint)
          outputs.solids << [scale_up(path), path_color]
          # And get the next pair of cells
          endpoint = next_endpoint
          next_endpoint = breadth_first_search.came_from[endpoint]
          # Continue till there are no more cells
        end
      end
    end
  
    # Renders the Dijkstra search on the second grid
    def render_dijkstra
    end
  
    def render_dijkstra_heat_map
      dijkstra_search.cost_so_far.each do |visited_cell, cost|
        max_cost = (grid.width + grid.height) #* 5
        alpha = 255.to_i * cost.to_i / max_cost.to_i
        outputs.solids << [move_and_scale_up(visited_cell), red, alpha]
      end
    end
  
    def render_dijkstra_path
      # If the search found the target
      if dijkstra_search.came_from.has_key?(state.target)
        # Get the target and the cell it came from
        endpoint = state.target
        next_endpoint = dijkstra_search.came_from[endpoint]
        while endpoint and next_endpoint
          # Draw a path between them
          path = get_path_between(endpoint, next_endpoint)
          outputs.solids << [move_and_scale_up(path), path_color]
  
          # Shift one cell down the path
          endpoint = next_endpoint
          next_endpoint = dijkstra_search.came_from[endpoint]
  
          # Repeat till the end of the path
        end
      end
    end
  
    # Renders the star on both grids
    def render_star
      outputs.sprites << [scale_up(state.star), 'star.png']
      outputs.sprites << [move_and_scale_up(state.star), 'star.png']
    end
  
    # Renders the target on both grids
    def render_target
      outputs.sprites << [scale_up(state.target), 'target.png']
      outputs.sprites << [move_and_scale_up(state.target), 'target.png']
    end
  
    def render_hills
      state.hills.each_key do |hill|
        outputs.solids << [scale_up(hill), hill_color]
        outputs.solids << [move_and_scale_up(hill), hill_color]
      end
    end
  
    # Draws the walls on both grids
    def render_walls
      state.walls.each_key do |wall|
        outputs.solids << [scale_up(wall), wall_color]
        outputs.solids << [move_and_scale_up(wall), wall_color]
      end
    end
  
    def get_path_between(cell_one, cell_two)
      path = nil
      if cell_one.x == cell_two.x
        if cell_one.y < cell_two.y
          path = [cell_one.x + 0.3, cell_one.y + 0.3, 0.4, 1.4]
        else
          path = [cell_two.x + 0.3, cell_two.y + 0.3, 0.4, 1.4]
        end
      else
        if cell_one.x < cell_two.x
          path = [cell_one.x + 0.3, cell_one.y + 0.3, 1.4, 0.4]
        else
          path = [cell_two.x + 0.3, cell_two.y + 0.3, 1.4, 0.4]
        end
      end
      path
    end
  
    # Representation of how far away visited cells are from the star
    # Replaces the render_visited method
    # Visually demonstrates the effectiveness of early exit for pathfinding
    def render_breadth_first_search_heat_map
      breadth_first_search.visited.each_key do | visited_cell |
        distance = (state.star.x - visited_cell.x).abs + (state.star.y - visited_cell.y).abs
        max_distance = grid.width + grid.height
        alpha = 255.to_i * distance.to_i / max_distance.to_i
        outputs.solids << [scale_up(visited_cell), red, alpha]
      end
    end
  
    # Translates the given cell grid.width + 1 to the right and then scales up
    # Used to draw cells for the second grid
    # This method does not work for lines,
    # so separate methods exist for the grid lines
    def move_and_scale_up(cell)
      cell_clone = cell.clone
      cell_clone.x += grid.width + 1
      scale_up(cell_clone)
    end
  
    # In code, the cells are represented as 1x1 rectangles
    # When drawn, the cells are larger than 1x1 rectangles
    # This method is used to scale up cells, and lines
    # Objects are scaled up according to the grid.cell_size variable
    # This allows for easy customization of the visual scale of the grid
    def scale_up(cell)
      # Prevents the original value of cell from being edited
      cell = cell.clone
  
      # If cell is just an x and y coordinate
      if cell.size == 2
        # Add a width and height of 1
        cell << 1
        cell << 1
      end
  
      # Scale all the values up
      cell.map! { |value| value * grid.cell_size }
  
      # Returns the scaled up cell
      cell
    end
  
    # Handles user input every tick so the grid can be edited
    # Separate input detection and processing is needed
    # For example: Adding walls is started by clicking down on a hill,
    # but the mouse doesn't need to remain over hills to add walls
    def input
      # If the mouse was lifted this tick
      if inputs.mouse.up
        # Set current input to none
        state.user_input = :none
      end
  
      # If the mouse was clicked this tick
      if inputs.mouse.down
        # Determine what the user is editing and edit the state.user_input variable
        determine_input
      end
  
      # Process user input based on user_input variable and current mouse position
      process_input
    end
  
    # Determines what the user is editing and stores the value
    # This method is called the tick the mouse is clicked
    # Storing the value allows the user to continue the same edit as long as the
    # mouse left click is held
    def determine_input
      # If the mouse is over the star in the first grid
      if mouse_over_star?
        # The user is editing the star from the first grid
        state.user_input = :star
      # If the mouse is over the star in the second grid
      elsif mouse_over_star2?
        # The user is editing the star from the second grid
        state.user_input = :star2
      # If the mouse is over the target in the first grid
      elsif mouse_over_target?
        # The user is editing the target from the first grid
        state.user_input = :target
      # If the mouse is over the target in the second grid
      elsif mouse_over_target2?
        # The user is editing the target from the second grid
        state.user_input = :target2
      # If the mouse is over a wall in the first grid
      elsif mouse_over_wall?
        # The user is removing a wall from the first grid
        state.user_input = :remove_wall
      # If the mouse is over a wall in the second grid
      elsif mouse_over_wall2?
        # The user is removing a wall from the second grid
        state.user_input = :remove_wall2
      # If the mouse is over a hill in the first grid
      elsif mouse_over_hill?
        # The user is adding a wall from the first grid
        state.user_input = :add_wall
      # If the mouse is over a hill in the second grid
      elsif mouse_over_hill2?
        # The user is adding a wall from the second grid
        state.user_input = :add_wall2
      # If the mouse is over the first grid
      elsif mouse_over_grid?
        # The user is adding a hill from the first grid
        state.user_input = :add_hill
      # If the mouse is over the second grid
      elsif mouse_over_grid2?
        # The user is adding a hill from the second grid
        state.user_input = :add_hill2
      end
    end
  
    # Processes click and drag based on what the user is currently dragging
    def process_input
      if state.user_input == :star
        input_star
      elsif state.user_input == :star2
        input_star2
      elsif state.user_input == :target
        input_target
      elsif state.user_input == :target2
        input_target2
      elsif state.user_input == :remove_wall
        input_remove_wall
      elsif state.user_input == :remove_wall2
        input_remove_wall2
      elsif state.user_input == :add_hill
        input_add_hill
      elsif state.user_input == :add_hill2
        input_add_hill2
      elsif state.user_input == :add_wall
        input_add_wall
      elsif state.user_input == :add_wall2
        input_add_wall2
      end
    end
  
    # Calculates the two searches
    def calc
      # If the searches have not started
      if breadth_first_search.visited.empty?
        # Calculate the two searches
        calc_breadth_first
        calc_dijkstra
      end
    end
  
  
    def calc_breadth_first
      # Sets up the Breadth First Search
      breadth_first_search.visited[state.star]   = true
      breadth_first_search.frontier              << state.star
      breadth_first_search.came_from[state.star] = nil
  
      until breadth_first_search.frontier.empty?
        return if breadth_first_search.visited.has_key?(state.target)
        # A step in the search
        # Takes the next frontier cell
        new_frontier = breadth_first_search.frontier.shift
        # For each of its neighbors
        adjacent_neighbors(new_frontier).each do | neighbor |
          # That have not been visited and are not walls
          unless breadth_first_search.visited.has_key?(neighbor) || state.walls.has_key?(neighbor)
            # Add them to the frontier and mark them as visited in the first grid
            breadth_first_search.visited[neighbor] = true
            breadth_first_search.frontier << neighbor
            # Remember which cell the neighbor came from
            breadth_first_search.came_from[neighbor] = new_frontier
          end
        end
      end
    end
  
    # Calculates the Dijkstra Search from the beginning to the end
  
    def calc_dijkstra
      # The initial values for the Dijkstra search
      dijkstra_search.frontier                << [state.star, 0]
      dijkstra_search.came_from[state.star]   = nil
      dijkstra_search.cost_so_far[state.star] = 0
  
      # Until their are no more cells to be explored
      until dijkstra_search.frontier.empty?
        # Get the next cell to be explored from
        # We get the first element of the array which is the cell. The second element is the priority.
        current = dijkstra_search.frontier.shift[0]
  
        # Stop the search if we found the target
        return if current == state.target
  
        # For each of the neighbors
        adjacent_neighbors(current).each do | neighbor |
          # Unless this cell is a wall or has already been explored.
          unless dijkstra_search.came_from.has_key?(neighbor) or state.walls.has_key?(neighbor)
            # Calculate the movement cost of getting to this cell and memo
            new_cost = dijkstra_search.cost_so_far[current] + cost(neighbor)
            dijkstra_search.cost_so_far[neighbor] = new_cost
  
            # Add this neighbor to the cells too be explored
            dijkstra_search.frontier << [neighbor, new_cost]
            dijkstra_search.came_from[neighbor] = current
          end
        end
  
        # Sort the frontier so exploration occurs that have a low cost so far.
        # My implementation of a priority queue
        dijkstra_search.frontier = dijkstra_search.frontier.sort_by {|cell, priority| priority}
      end
    end
  
    def cost(cell)
      if state.hills.has_key?(cell)
        return 5
      else
        return 1
      end
    end
  
  
  
  
    # Moves the star to the cell closest to the mouse in the first grid
    # Only resets the search if the star changes position
    # Called whenever the user is editing the star (puts mouse down on star)
    def input_star
      old_star = state.star.clone
      unless cell_closest_to_mouse == state.target
        state.star = cell_closest_to_mouse
      end
      unless old_star == state.star
        reset_search
      end
    end
  
    # Moves the star to the cell closest to the mouse in the second grid
    # Only resets the search if the star changes position
    # Called whenever the user is editing the star (puts mouse down on star)
    def input_star2
      old_star = state.star.clone
      unless cell_closest_to_mouse2 == state.target
        state.star = cell_closest_to_mouse2
      end
      unless old_star == state.star
        reset_search
      end
    end
  
    # Moves the target to the grid closest to the mouse in the first grid
    # Only reset_searchs the search if the target changes position
    # Called whenever the user is editing the target (puts mouse down on target)
    def input_target
      old_target = state.target.clone
      unless cell_closest_to_mouse == state.star
        state.target = cell_closest_to_mouse
      end
      unless old_target == state.target
        reset_search
      end
    end
  
    # Moves the target to the cell closest to the mouse in the second grid
    # Only reset_searchs the search if the target changes position
    # Called whenever the user is editing the target (puts mouse down on target)
    def input_target2
      old_target = state.target.clone
      unless cell_closest_to_mouse2 == state.star
        state.target = cell_closest_to_mouse2
      end
      unless old_target == state.target
        reset_search
      end
    end
  
    # Removes walls in the first grid that are under the cursor
    def input_remove_wall
      # The mouse needs to be inside the grid, because we only want to remove walls
      # the cursor is directly over
      # Recalculations should only occur when a wall is actually deleted
      if mouse_over_grid?
        if state.walls.has_key?(cell_closest_to_mouse) or state.hills.has_key?(cell_closest_to_mouse)
          state.walls.delete(cell_closest_to_mouse)
          state.hills.delete(cell_closest_to_mouse)
          reset_search
        end
      end
    end
  
    # Removes walls in the second grid that are under the cursor
    def input_remove_wall2
      # The mouse needs to be inside the grid, because we only want to remove walls
      # the cursor is directly over
      # Recalculations should only occur when a wall is actually deleted
      if mouse_over_grid2?
        if state.walls.has_key?(cell_closest_to_mouse2) or state.hills.has_key?(cell_closest_to_mouse2)
          state.walls.delete(cell_closest_to_mouse2)
          state.hills.delete(cell_closest_to_mouse2)
          reset_search
        end
      end
    end
  
    # Adds a hill in the first grid in the cell the mouse is over
    def input_add_hill
      if mouse_over_grid?
        unless state.hills.has_key?(cell_closest_to_mouse)
          state.hills[cell_closest_to_mouse] = true
          reset_search
        end
      end
    end
  
  
    # Adds a hill in the second grid in the cell the mouse is over
    def input_add_hill2
      if mouse_over_grid2?
        unless state.hills.has_key?(cell_closest_to_mouse2)
          state.hills[cell_closest_to_mouse2] = true
          reset_search
        end
      end
    end
  
    # Adds a wall in the first grid in the cell the mouse is over
    def input_add_wall
      if mouse_over_grid?
        unless state.walls.has_key?(cell_closest_to_mouse)
          state.hills.delete(cell_closest_to_mouse)
          state.walls[cell_closest_to_mouse] = true
          reset_search
        end
      end
    end
  
    # Adds a wall in the second grid in the cell the mouse is over
    def input_add_wall2
      if mouse_over_grid2?
        unless state.walls.has_key?(cell_closest_to_mouse2)
          state.hills.delete(cell_closest_to_mouse2)
          state.walls[cell_closest_to_mouse2] = true
          reset_search
        end
      end
    end
  
    # Whenever the user edits the grid,
    # The search has to be reset_searchd upto the current step
    # with the current grid as the initial state of the grid
    def reset_search
      breadth_first_search.visited    = {}
      breadth_first_search.frontier   = []
      breadth_first_search.came_from  = {}
  
      dijkstra_search.frontier    = []
      dijkstra_search.came_from   = {}
      dijkstra_search.cost_so_far = {}
    end
  
  
  
    # Returns a list of adjacent cells
    # Used to determine what the next cells to be added to the frontier are
    def adjacent_neighbors(cell)
      neighbors = []
  
      # Gets all the valid neighbors into the array
      # From southern neighbor, clockwise
      neighbors << [cell.x    , cell.y - 1] unless cell.y == 0
      neighbors << [cell.x - 1, cell.y    ] unless cell.x == 0
      neighbors << [cell.x    , cell.y + 1] unless cell.y == grid.height - 1
      neighbors << [cell.x + 1, cell.y    ] unless cell.x == grid.width - 1
  
      # Sorts the neighbors so the rendered path is a zigzag path
      # Cells in a diagonal direction are given priority
      # Comment this line to see the difference
      neighbors = neighbors.sort_by { |neighbor_x, neighbor_y|  proximity_to_star(neighbor_x, neighbor_y) }
  
      neighbors
    end
  
    # Finds the vertical and horizontal distance of a cell from the star
    # and returns the larger value
    # This method is used to have a zigzag pattern in the rendered path
    # A cell that is [5, 5] from the star,
    # is explored before over a cell that is [0, 7] away.
    # So, if possible, the search tries to go diagonal (zigzag) first
    def proximity_to_star(x, y)
      distance_x = (state.star.x - x).abs
      distance_y = (state.star.y - y).abs
  
      if distance_x > distance_y
        return distance_x
      else
        return distance_y
      end
    end
  
    # When the user grabs the star and puts their cursor to the far right
    # and moves up and down, the star is supposed to move along the grid as well
    # Finding the cell closest to the mouse helps with this
    def cell_closest_to_mouse
      # Closest cell to the mouse in the first grid
      x = (inputs.mouse.point.x / grid.cell_size).to_i
      y = (inputs.mouse.point.y / grid.cell_size).to_i
      # Bound x and y to the grid
      x = grid.width - 1 if x > grid.width - 1
      y = grid.height - 1 if y > grid.height - 1
      # Return closest cell
      [x, y]
    end
  
    # When the user grabs the star and puts their cursor to the far right
    # and moves up and down, the star is supposed to move along the grid as well
    # Finding the cell closest to the mouse in the second grid helps with this
    def cell_closest_to_mouse2
      # Closest cell grid to the mouse in the second
      x = (inputs.mouse.point.x / grid.cell_size).to_i
      y = (inputs.mouse.point.y / grid.cell_size).to_i
      # Translate the cell to the first grid
      x -= grid.width + 1
      # Bound x and y to the first grid
      x = 0 if x < 0
      y = 0 if y < 0
      x = grid.width - 1 if x > grid.width - 1
      y = grid.height - 1 if y > grid.height - 1
      # Return closest cell
      [x, y]
    end
  
    # Signal that the user is going to be moving the star from the first grid
    def mouse_over_star?
      inputs.mouse.point.inside_rect?(scale_up(state.star))
    end
  
    # Signal that the user is going to be moving the star from the second grid
    def mouse_over_star2?
      inputs.mouse.point.inside_rect?(move_and_scale_up(state.star))
    end
  
    # Signal that the user is going to be moving the target from the first grid
    def mouse_over_target?
      inputs.mouse.point.inside_rect?(scale_up(state.target))
    end
  
    # Signal that the user is going to be moving the target from the second grid
    def mouse_over_target2?
      inputs.mouse.point.inside_rect?(move_and_scale_up(state.target))
    end
  
    # Signal that the user is going to be removing walls from the first grid
    def mouse_over_wall?
      state.walls.each_key do | wall |
        return true if inputs.mouse.point.inside_rect?(scale_up(wall))
      end
  
      false
    end
  
    # Signal that the user is going to be removing walls from the second grid
    def mouse_over_wall2?
      state.walls.each_key do | wall |
        return true if inputs.mouse.point.inside_rect?(move_and_scale_up(wall))
      end
  
      false
    end
  
    # Signal that the user is going to be removing hills from the first grid
    def mouse_over_hill?
      state.hills.each_key do | hill |
        return true if inputs.mouse.point.inside_rect?(scale_up(hill))
      end
  
      false
    end
  
    # Signal that the user is going to be removing hills from the second grid
    def mouse_over_hill2?
      state.hills.each_key do | hill |
        return true if inputs.mouse.point.inside_rect?(move_and_scale_up(hill))
      end
  
      false
    end
  
    # Signal that the user is going to be adding walls from the first grid
    def mouse_over_grid?
      inputs.mouse.point.inside_rect?(scale_up(grid.rect))
    end
  
    # Signal that the user is going to be adding walls from the second grid
    def mouse_over_grid2?
      inputs.mouse.point.inside_rect?(move_and_scale_up(grid.rect))
    end
  
    # These methods provide handy aliases to colors
  
    # Light brown
    def unvisited_color
      [221, 212, 213]
    end
  
    # Camo Green
    def wall_color
      [134, 134, 120]
    end
  
    # Pastel White
    def path_color
      [231, 230, 228]
    end
  
    def red
      [255, 0, 0]
    end
  
    # A Green
    def hill_color
      [139, 173, 132]
    end
  
    # Makes code more concise
    def grid
      state.grid
    end
  
    def breadth_first_search
      state.breadth_first_search
    end
  
    def dijkstra_search
      state.dijkstra_search
    end
  end
  
  # Method that is called by DragonRuby periodically
  # Used for updating animations and calculations
  def tick args
  
    # Pressing r will reset the application
    if args.inputs.keyboard.key_down.r
      args.gtk.reset
      reset
      return
    end
  
    # Every tick, new args are passed, and the Dijkstra tick method is called
    $movement_costs ||= Movement_Costs.new
    $movement_costs.args = args
    $movement_costs.tick
  end
  
  
  def reset
    $movement_costs = nil
  end

#+end_src

*** Path Finding Algorithms - Heuristic - main.rb
#+begin_src ruby
  # ./samples/13_path_finding_algorithms/06_heuristic/app/main.rb
  # This program is inspired by https://www.redblobgames.com/pathfinding/a-star/introduction.html
  
  # This time the heuristic search still explored less of the grid, hence finishing faster.
  # However, it did not find the shortest path between the star and the target.
  
  # The only difference between this app and Heuristic is the change of the starting position.
  
  class Heuristic_With_Walls
    attr_gtk
  
    def tick
      defaults
      render
      input
      # If animation is playing, and max steps have not been reached
      # Move the search a step forward
      if state.play && state.current_step < state.max_steps
        # Variable that tells the program what step to recalculate up to
        state.current_step += 1
        move_searches_one_step_forward
      end
    end
  
    def defaults
      # Variables to edit the size and appearance of the grid
      # Freely customizable to user's liking
      grid.width     ||= 15
      grid.height    ||= 15
      grid.cell_size ||= 40
      grid.rect      ||= [0, 0, grid.width, grid.height]
  
      grid.star      ||= [0, 2]
      grid.target    ||= [14, 12]
      grid.walls     ||= {}
      # There are no hills in the Heuristic Search Demo
  
      # What the user is currently editing on the grid
      # We store this value, because we want to remember the value even when
      # the user's cursor is no longer over what they're interacting with, but
      # they are still clicking down on the mouse.
      state.user_input ||= :none
  
      # These variables allow the breadth first search to take place
      # Came_from is a hash with a key of a cell and a value of the cell that was expanded from to find the key.
      # Used to prevent searching cells that have already been found
      # and to trace a path from the target back to the starting point.
      # Frontier is an array of cells to expand the search from.
      # The search is over when there are no more cells to search from.
      # Path stores the path from the target to the star, once the target has been found
      # It prevents calculating the path every tick.
      bfs.came_from  ||= {}
      bfs.frontier   ||= []
      bfs.path       ||= []
  
      heuristic.came_from ||= {}
      heuristic.frontier  ||= []
      heuristic.path      ||= []
  
      # Stores which step of the animation is being rendered
      # When the user moves the star or messes with the walls,
      # the searches are recalculated up to this step
  
      # Unless the current step has a value
      unless state.current_step
        # Set the current step to 10
        state.current_step = 10
        # And calculate the searches up to step 10
        recalculate_searches
      end
  
      # At some step the animation will end,
      # and further steps won't change anything (the whole grid will be explored)
      # This step is roughly the grid's width * height
      # When anim_steps equals max_steps no more calculations will occur
      # and the slider will be at the end
      state.max_steps = grid.width * grid.height
  
      # Whether the animation should play or not
      # If true, every tick moves anim_steps forward one
      # Pressing the stepwise animation buttons will pause the animation
      # An if statement instead of the ||= operator is used for assigning a boolean value.
      # The || operator does not differentiate between nil and false.
      if state.play == nil
        state.play = false
      end
  
      # Store the rects of the buttons that control the animation
      # They are here for user customization
      # Editing these might require recentering the text inside them
      # Those values can be found in the render_button methods
      buttons.left   = [470, 600, 50, 50]
      buttons.center = [520, 600, 200, 50]
      buttons.right  = [720, 600, 50, 50]
  
      # The variables below are related to the slider
      # They allow the user to customize them
      # They also give a central location for the render and input methods to get
      # information from
      # x & y are the coordinates of the leftmost part of the slider line
      slider.x = 440
      slider.y = 675
      # This is the width of the line
      slider.w = 360
      # This is the offset for the circle
      # Allows the center of the circle to be on the line,
      # as opposed to the upper right corner
      slider.offset = 20
      # This is the spacing between each of the notches on the slider
      # Notches are places where the circle can rest on the slider line
      # There needs to be a notch for each step before the maximum number of steps
      slider.spacing = slider.w.to_f / state.max_steps.to_f
    end
  
    # All methods with render draw stuff on the screen
    # UI has buttons, the slider, and labels
    # The search specific rendering occurs in the respective methods
    def render
      render_ui
      render_bfs
      render_heuristic
    end
  
    def render_ui
      render_buttons
      render_slider
      render_labels
    end
  
    def render_buttons
      render_left_button
      render_center_button
      render_right_button
    end
  
    def render_bfs
      render_bfs_grid
      render_bfs_star
      render_bfs_target
      render_bfs_visited
      render_bfs_walls
      render_bfs_frontier
      render_bfs_path
    end
  
    def render_heuristic
      render_heuristic_grid
      render_heuristic_star
      render_heuristic_target
      render_heuristic_visited
      render_heuristic_walls
      render_heuristic_frontier
      render_heuristic_path
    end
  
    # This method handles user input every tick
    def input
      # Check and handle button input
      input_buttons
  
      # If the mouse was lifted this tick
      if inputs.mouse.up
        # Set current input to none
        state.user_input = :none
      end
  
      # If the mouse was clicked this tick
      if inputs.mouse.down
        # Determine what the user is editing and appropriately edit the state.user_input variable
        determine_input
      end
  
      # Process user input based on user_input variable and current mouse position
      process_input
    end
  
    # Determines what the user is editing
    # This method is called when the mouse is clicked down
    def determine_input
      if mouse_over_slider?
        state.user_input = :slider
      # If the mouse is over the star in the first grid
      elsif bfs_mouse_over_star?
        # The user is editing the star from the first grid
        state.user_input = :bfs_star
      # If the mouse is over the star in the second grid
      elsif heuristic_mouse_over_star?
        # The user is editing the star from the second grid
        state.user_input = :heuristic_star
      # If the mouse is over the target in the first grid
      elsif bfs_mouse_over_target?
        # The user is editing the target from the first grid
        state.user_input = :bfs_target
      # If the mouse is over the target in the second grid
      elsif heuristic_mouse_over_target?
        # The user is editing the target from the second grid
        state.user_input = :heuristic_target
      # If the mouse is over a wall in the first grid
      elsif bfs_mouse_over_wall?
        # The user is removing a wall from the first grid
        state.user_input = :bfs_remove_wall
      # If the mouse is over a wall in the second grid
      elsif heuristic_mouse_over_wall?
        # The user is removing a wall from the second grid
        state.user_input = :heuristic_remove_wall
      # If the mouse is over the first grid
      elsif bfs_mouse_over_grid?
        # The user is adding a wall from the first grid
        state.user_input = :bfs_add_wall
      # If the mouse is over the second grid
      elsif heuristic_mouse_over_grid?
        # The user is adding a wall from the second grid
        state.user_input = :heuristic_add_wall
      end
    end
  
    # Processes click and drag based on what the user is currently dragging
    def process_input
      if state.user_input == :slider
        process_input_slider
      elsif state.user_input == :bfs_star
        process_input_bfs_star
      elsif state.user_input == :heuristic_star
        process_input_heuristic_star
      elsif state.user_input == :bfs_target
        process_input_bfs_target
      elsif state.user_input == :heuristic_target
        process_input_heuristic_target
      elsif state.user_input == :bfs_remove_wall
        process_input_bfs_remove_wall
      elsif state.user_input == :heuristic_remove_wall
        process_input_heuristic_remove_wall
      elsif state.user_input == :bfs_add_wall
        process_input_bfs_add_wall
      elsif state.user_input == :heuristic_add_wall
        process_input_heuristic_add_wall
      end
    end
  
    def render_slider
      # Using primitives hides the line under the white circle of the slider
      # Draws the line
      outputs.primitives << [slider.x, slider.y, slider.x + slider.w, slider.y].line
      # The circle needs to be offset so that the center of the circle
      # overlaps the line instead of the upper right corner of the circle
      # The circle's x value is also moved based on the current seach step
      circle_x = (slider.x - slider.offset) + (state.current_step * slider.spacing)
      circle_y = (slider.y - slider.offset)
      circle_rect = [circle_x, circle_y, 37, 37]
      outputs.primitives << [circle_rect, 'circle-white.png'].sprite
    end
  
    def render_labels
      outputs.labels << [205, 625, "Breadth First Search"]
      outputs.labels << [820, 625, "Heuristic Best-First Search"]
    end
  
    def render_left_button
      # Draws the button_color button, and a black border
      # The border separates the buttons visually
      outputs.solids  << [buttons.left, button_color]
      outputs.borders << [buttons.left]
  
      # Renders an explanatory label in the center of the button
      # Explains to the user what the button does
      # If the button size is changed, the label might need to be edited as well
      # to keep the label in the center of the button
      label_x = buttons.left.x + 20
      label_y = buttons.left.y + 35
      outputs.labels  << [label_x, label_y, "<"]
    end
  
    def render_center_button
      # Draws the button_color button, and a black border
      # The border separates the buttons visually
      outputs.solids  << [buttons.center, button_color]
      outputs.borders << [buttons.center]
  
      # Renders an explanatory label in the center of the button
      # Explains to the user what the button does
      # If the button size is changed, the label might need to be edited as well
      # to keep the label in the center of the button
      label_x    = buttons.center.x + 37
      label_y    = buttons.center.y + 35
      label_text = state.play ? "Pause Animation" : "Play Animation"
      outputs.labels << [label_x, label_y, label_text]
    end
  
    def render_right_button
      # Draws the button_color button, and a black border
      # The border separates the buttons visually
      outputs.solids  << [buttons.right, button_color]
      outputs.borders << [buttons.right]
  
      # Renders an explanatory label in the center of the button
      # Explains to the user what the button does
      label_x = buttons.right.x + 20
      label_y = buttons.right.y + 35
      outputs.labels  << [label_x, label_y, ">"]
    end
  
    def render_bfs_grid
      # A large rect the size of the grid
      outputs.solids << [bfs_scale_up(grid.rect), default_color]
  
      # The vertical grid lines
      for x in 0..grid.width
        outputs.lines << bfs_vertical_line(x)
      end
  
      # The horizontal grid lines
      for y in 0..grid.height
        outputs.lines << bfs_horizontal_line(y)
      end
    end
  
    def render_heuristic_grid
      # A large rect the size of the grid
      outputs.solids << [heuristic_scale_up(grid.rect), default_color]
  
      # The vertical grid lines
      for x in 0..grid.width
        outputs.lines << heuristic_vertical_line(x)
      end
  
      # The horizontal grid lines
      for y in 0..grid.height
        outputs.lines << heuristic_horizontal_line(y)
      end
    end
  
    # Returns a vertical line for a column of the first grid
    def bfs_vertical_line column
      bfs_scale_up([column, 0, column, grid.height])
    end
  
    # Returns a horizontal line for a column of the first grid
    def bfs_horizontal_line row
      bfs_scale_up([0, row, grid.width, row])
    end
  
    # Returns a vertical line for a column of the second grid
    def heuristic_vertical_line column
      bfs_scale_up([column + grid.width + 1, 0, column + grid.width + 1, grid.height])
    end
  
    # Returns a horizontal line for a column of the second grid
    def heuristic_horizontal_line row
      bfs_scale_up([grid.width + 1, row, grid.width + grid.width + 1, row])
    end
  
    # Renders the star on the first grid
    def render_bfs_star
      outputs.sprites << [bfs_scale_up(grid.star), 'star.png']
    end
  
    # Renders the star on the second grid
    def render_heuristic_star
      outputs.sprites << [heuristic_scale_up(grid.star), 'star.png']
    end
  
    # Renders the target on the first grid
    def render_bfs_target
      outputs.sprites << [bfs_scale_up(grid.target), 'target.png']
    end
  
    # Renders the target on the second grid
    def render_heuristic_target
      outputs.sprites << [heuristic_scale_up(grid.target), 'target.png']
    end
  
    # Renders the walls on the first grid
    def render_bfs_walls
      grid.walls.each_key do | wall |
        outputs.solids << [bfs_scale_up(wall), wall_color]
      end
    end
  
    # Renders the walls on the second grid
    def render_heuristic_walls
      grid.walls.each_key do | wall |
        outputs.solids << [heuristic_scale_up(wall), wall_color]
      end
    end
  
    # Renders the visited cells on the first grid
    def render_bfs_visited
      bfs.came_from.each_key do | visited_cell |
        outputs.solids << [bfs_scale_up(visited_cell), visited_color]
      end
    end
  
    # Renders the visited cells on the second grid
    def render_heuristic_visited
      heuristic.came_from.each_key do | visited_cell |
        outputs.solids << [heuristic_scale_up(visited_cell), visited_color]
      end
    end
  
    # Renders the frontier cells on the first grid
    def render_bfs_frontier
      bfs.frontier.each do | frontier_cell |
        outputs.solids << [bfs_scale_up(frontier_cell), frontier_color, 200]
      end
    end
  
    # Renders the frontier cells on the second grid
    def render_heuristic_frontier
      heuristic.frontier.each do | frontier_cell |
        outputs.solids << [heuristic_scale_up(frontier_cell), frontier_color, 200]
      end
    end
  
    # Renders the path found by the breadth first search on the first grid
    def render_bfs_path
      bfs.path.each do | path |
        outputs.solids << [bfs_scale_up(path), path_color]
      end
    end
  
    # Renders the path found by the heuristic search on the second grid
    def render_heuristic_path
      heuristic.path.each do | path |
        outputs.solids << [heuristic_scale_up(path), path_color]
      end
    end
  
    # Returns the rect for the path between two cells based on their relative positions
    def get_path_between(cell_one, cell_two)
      path = nil
  
      # If cell one is above cell two
      if cell_one.x == cell_two.x and cell_one.y > cell_two.y
        # Path starts from the center of cell two and moves upward to the center of cell one
        path = [cell_two.x + 0.3, cell_two.y + 0.3, 0.4, 1.4]
      # If cell one is below cell two
      elsif cell_one.x == cell_two.x and cell_one.y < cell_two.y
        # Path starts from the center of cell one and moves upward to the center of cell two
        path = [cell_one.x + 0.3, cell_one.y + 0.3, 0.4, 1.4]
      # If cell one is to the left of cell two
      elsif cell_one.x > cell_two.x and cell_one.y == cell_two.y
        # Path starts from the center of cell two and moves rightward to the center of cell one
        path = [cell_two.x + 0.3, cell_two.y + 0.3, 1.4, 0.4]
      # If cell one is to the right of cell two
      elsif cell_one.x < cell_two.x and cell_one.y == cell_two.y
        # Path starts from the center of cell one and moves rightward to the center of cell two
        path = [cell_one.x + 0.3, cell_one.y + 0.3, 1.4, 0.4]
      end
  
      path
    end
  
    # In code, the cells are represented as 1x1 rectangles
    # When drawn, the cells are larger than 1x1 rectangles
    # This method is used to scale up cells, and lines
    # Objects are scaled up according to the grid.cell_size variable
    # This allows for easy customization of the visual scale of the grid
    # This method scales up cells for the first grid
    def bfs_scale_up(cell)
      # Prevents the original value of cell from being edited
      cell = cell.clone
  
      # If cell is just an x and y coordinate
      if cell.size == 2
        # Add a width and height of 1
        cell << 1
        cell << 1
      end
  
      # Scale all the values up
      cell.map! { |value| value * grid.cell_size }
  
      # Returns the scaled up cell
      cell
    end
  
    # Translates the given cell grid.width + 1 to the right and then scales up
    # Used to draw cells for the second grid
    # This method does not work for lines,
    # so separate methods exist for the grid lines
    def heuristic_scale_up(cell)
      # Prevents the original value of cell from being edited
      cell = cell.clone
      # Translates the cell to the second grid equivalent
      cell.x += grid.width + 1
      # Proceeds as if scaling up for the first grid
      bfs_scale_up(cell)
    end
  
    # Checks and handles input for the buttons
    # Called when the mouse is lifted
    def input_buttons
      input_left_button
      input_center_button
      input_right_button
    end
  
    # Checks if the previous step button is clicked
    # If it is, it pauses the animation and moves the search one step backward
    def input_left_button
      if left_button_clicked?
        state.play = false
        state.current_step -= 1
        recalculate_searches
      end
    end
  
    # Controls the play/pause button
    # Inverses whether the animation is playing or not when clicked
    def input_center_button
      if center_button_clicked? || inputs.keyboard.key_down.space
        state.play = !state.play
      end
    end
  
    # Checks if the next step button is clicked
    # If it is, it pauses the animation and moves the search one step forward
    def input_right_button
      if right_button_clicked?
        state.play = false
        state.current_step += 1
        move_searches_one_step_forward
      end
    end
  
    # These methods detect when the buttons are clicked
    def left_button_clicked?
      inputs.mouse.point.inside_rect?(buttons.left) && inputs.mouse.up
    end
  
    def center_button_clicked?
      inputs.mouse.point.inside_rect?(buttons.center) && inputs.mouse.up
    end
  
    def right_button_clicked?
      inputs.mouse.point.inside_rect?(buttons.right) && inputs.mouse.up
    end
  
  
    # Signal that the user is going to be moving the slider
    # Is the mouse over the circle of the slider?
    def mouse_over_slider?
      circle_x = (slider.x - slider.offset) + (state.current_step * slider.spacing)
      circle_y = (slider.y - slider.offset)
      circle_rect = [circle_x, circle_y, 37, 37]
      inputs.mouse.point.inside_rect?(circle_rect)
    end
  
    # Signal that the user is going to be moving the star from the first grid
    def bfs_mouse_over_star?
      inputs.mouse.point.inside_rect?(bfs_scale_up(grid.star))
    end
  
    # Signal that the user is going to be moving the star from the second grid
    def heuristic_mouse_over_star?
      inputs.mouse.point.inside_rect?(heuristic_scale_up(grid.star))
    end
  
    # Signal that the user is going to be moving the target from the first grid
    def bfs_mouse_over_target?
      inputs.mouse.point.inside_rect?(bfs_scale_up(grid.target))
    end
  
    # Signal that the user is going to be moving the target from the second grid
    def heuristic_mouse_over_target?
      inputs.mouse.point.inside_rect?(heuristic_scale_up(grid.target))
    end
  
    # Signal that the user is going to be removing walls from the first grid
    def bfs_mouse_over_wall?
      grid.walls.each_key do | wall |
        return true if inputs.mouse.point.inside_rect?(bfs_scale_up(wall))
      end
  
      false
    end
  
    # Signal that the user is going to be removing walls from the second grid
    def heuristic_mouse_over_wall?
      grid.walls.each_key do | wall |
        return true if inputs.mouse.point.inside_rect?(heuristic_scale_up(wall))
      end
  
      false
    end
  
    # Signal that the user is going to be adding walls from the first grid
    def bfs_mouse_over_grid?
      inputs.mouse.point.inside_rect?(bfs_scale_up(grid.rect))
    end
  
    # Signal that the user is going to be adding walls from the second grid
    def heuristic_mouse_over_grid?
      inputs.mouse.point.inside_rect?(heuristic_scale_up(grid.rect))
    end
  
    # This method is called when the user is editing the slider
    # It pauses the animation and moves the white circle to the closest integer point
    # on the slider
    # Changes the step of the search to be animated
    def process_input_slider
      state.play = false
      mouse_x = inputs.mouse.point.x
  
      # Bounds the mouse_x to the closest x value on the slider line
      mouse_x = slider.x if mouse_x < slider.x
      mouse_x = slider.x + slider.w if mouse_x > slider.x + slider.w
  
      # Sets the current search step to the one represented by the mouse x value
      # The slider's circle moves due to the render_slider method using anim_steps
      state.current_step = ((mouse_x - slider.x) / slider.spacing).to_i
  
      recalculate_searches
    end
  
    # Moves the star to the cell closest to the mouse in the first grid
    # Only resets the search if the star changes position
    # Called whenever the user is editing the star (puts mouse down on star)
    def process_input_bfs_star
      old_star = grid.star.clone
      unless bfs_cell_closest_to_mouse == grid.target
        grid.star = bfs_cell_closest_to_mouse
      end
      unless old_star == grid.star
        recalculate_searches
      end
    end
  
    # Moves the star to the cell closest to the mouse in the second grid
    # Only resets the search if the star changes position
    # Called whenever the user is editing the star (puts mouse down on star)
    def process_input_heuristic_star
      old_star = grid.star.clone
      unless heuristic_cell_closest_to_mouse == grid.target
        grid.star = heuristic_cell_closest_to_mouse
      end
      unless old_star == grid.star
        recalculate_searches
      end
    end
  
    # Moves the target to the grid closest to the mouse in the first grid
    # Only recalculate_searchess the search if the target changes position
    # Called whenever the user is editing the target (puts mouse down on target)
    def process_input_bfs_target
      old_target = grid.target.clone
      unless bfs_cell_closest_to_mouse == grid.star
        grid.target = bfs_cell_closest_to_mouse
      end
      unless old_target == grid.target
        recalculate_searches
      end
    end
  
    # Moves the target to the cell closest to the mouse in the second grid
    # Only recalculate_searchess the search if the target changes position
    # Called whenever the user is editing the target (puts mouse down on target)
    def process_input_heuristic_target
      old_target = grid.target.clone
      unless heuristic_cell_closest_to_mouse == grid.star
        grid.target = heuristic_cell_closest_to_mouse
      end
      unless old_target == grid.target
        recalculate_searches
      end
    end
  
    # Removes walls in the first grid that are under the cursor
    def process_input_bfs_remove_wall
      # The mouse needs to be inside the grid, because we only want to remove walls
      # the cursor is directly over
      # Recalculations should only occur when a wall is actually deleted
      if bfs_mouse_over_grid?
        if grid.walls.has_key?(bfs_cell_closest_to_mouse)
          grid.walls.delete(bfs_cell_closest_to_mouse)
          recalculate_searches
        end
      end
    end
  
    # Removes walls in the second grid that are under the cursor
    def process_input_heuristic_remove_wall
      # The mouse needs to be inside the grid, because we only want to remove walls
      # the cursor is directly over
      # Recalculations should only occur when a wall is actually deleted
      if heuristic_mouse_over_grid?
        if grid.walls.has_key?(heuristic_cell_closest_to_mouse)
          grid.walls.delete(heuristic_cell_closest_to_mouse)
          recalculate_searches
        end
      end
    end
    # Adds a wall in the first grid in the cell the mouse is over
    def process_input_bfs_add_wall
      if bfs_mouse_over_grid?
        unless grid.walls.has_key?(bfs_cell_closest_to_mouse)
          grid.walls[bfs_cell_closest_to_mouse] = true
          recalculate_searches
        end
      end
    end
  
    # Adds a wall in the second grid in the cell the mouse is over
    def process_input_heuristic_add_wall
      if heuristic_mouse_over_grid?
        unless grid.walls.has_key?(heuristic_cell_closest_to_mouse)
          grid.walls[heuristic_cell_closest_to_mouse] = true
          recalculate_searches
        end
      end
    end
  
    # When the user grabs the star and puts their cursor to the far right
    # and moves up and down, the star is supposed to move along the grid as well
    # Finding the cell closest to the mouse helps with this
    def bfs_cell_closest_to_mouse
      # Closest cell to the mouse in the first grid
      x = (inputs.mouse.point.x / grid.cell_size).to_i
      y = (inputs.mouse.point.y / grid.cell_size).to_i
      # Bound x and y to the grid
      x = grid.width - 1 if x > grid.width - 1
      y = grid.height - 1 if y > grid.height - 1
      # Return closest cell
      [x, y]
    end
  
    # When the user grabs the star and puts their cursor to the far right
    # and moves up and down, the star is supposed to move along the grid as well
    # Finding the cell closest to the mouse in the second grid helps with this
    def heuristic_cell_closest_to_mouse
      # Closest cell grid to the mouse in the second
      x = (inputs.mouse.point.x / grid.cell_size).to_i
      y = (inputs.mouse.point.y / grid.cell_size).to_i
      # Translate the cell to the first grid
      x -= grid.width + 1
      # Bound x and y to the first grid
      x = 0 if x < 0
      y = 0 if y < 0
      x = grid.width - 1 if x > grid.width - 1
      y = grid.height - 1 if y > grid.height - 1
      # Return closest cell
      [x, y]
    end
  
    def recalculate_searches
      # Reset the searches
      bfs.came_from    = {}
      bfs.frontier     = []
      bfs.path         = []
      heuristic.came_from = {}
      heuristic.frontier  = []
      heuristic.path      = []
  
      # Move the searches forward to the current step
      state.current_step.times { move_searches_one_step_forward }
    end
  
    def move_searches_one_step_forward
      bfs_one_step_forward
      heuristic_one_step_forward
    end
  
    def bfs_one_step_forward
      return if bfs.came_from.has_key?(grid.target)
  
      # Only runs at the beginning of the search as setup.
      if bfs.came_from.empty?
        bfs.frontier << grid.star
        bfs.came_from[grid.star] = nil
      end
  
      # A step in the search
      unless bfs.frontier.empty?
        # Takes the next frontier cell
        new_frontier = bfs.frontier.shift
        # For each of its neighbors
        adjacent_neighbors(new_frontier).each do |neighbor|
          # That have not been visited and are not walls
          unless bfs.came_from.has_key?(neighbor) || grid.walls.has_key?(neighbor)
            # Add them to the frontier and mark them as visited
            bfs.frontier << neighbor
            bfs.came_from[neighbor] = new_frontier
          end
        end
      end
  
      # Sort the frontier so that cells that are in a zigzag pattern are prioritized over those in an line
      # Comment this line and let a path generate to see the difference
      bfs.frontier = bfs.frontier.sort_by {| cell | proximity_to_star(cell) }
  
      # If the search found the target
      if bfs.came_from.has_key?(grid.target)
        # Calculate the path between the target and star
        bfs_calc_path
      end
    end
  
    # Calculates the path between the target and star for the breadth first search
    # Only called when the breadth first search finds the target
    def bfs_calc_path
      # Start from the target
      endpoint = grid.target
      # And the cell it came from
      next_endpoint = bfs.came_from[endpoint]
      while endpoint and next_endpoint
        # Draw a path between these two cells and store it
        path = get_path_between(endpoint, next_endpoint)
        bfs.path << path
        # And get the next pair of cells
        endpoint = next_endpoint
        next_endpoint = bfs.came_from[endpoint]
        # Continue till there are no more cells
      end
    end
  
    # Moves the heuristic search forward one step
    # Can be called from tick while the animation is playing
    # Can also be called when recalculating the searches after the user edited the grid
    def heuristic_one_step_forward
      # Stop the search if the target has been found
      return if heuristic.came_from.has_key?(grid.target)
  
      # If the search has not begun
      if heuristic.came_from.empty?
        # Setup the search to begin from the star
        heuristic.frontier << grid.star
        heuristic.came_from[grid.star] = nil
      end
  
      # One step in the heuristic search
  
      # Unless there are no more cells to explore from
      unless heuristic.frontier.empty?
        # Get the next cell to explore from
        new_frontier = heuristic.frontier.shift
        # For each of its neighbors
        adjacent_neighbors(new_frontier).each do |neighbor|
          # That have not been visited and are not walls
          unless heuristic.came_from.has_key?(neighbor) || grid.walls.has_key?(neighbor)
            # Add them to the frontier and mark them as visited
            heuristic.frontier << neighbor
            heuristic.came_from[neighbor] = new_frontier
          end
        end
      end
  
      # Sort the frontier so that cells that are in a zigzag pattern are prioritized over those in an line
      heuristic.frontier = heuristic.frontier.sort_by {| cell | proximity_to_star(cell) }
      # Sort the frontier so cells that are close to the target are then prioritized
      heuristic.frontier = heuristic.frontier.sort_by {| cell | heuristic_heuristic(cell)  }
  
      # If the search found the target
      if heuristic.came_from.has_key?(grid.target)
        # Calculate the path between the target and star
        heuristic_calc_path
      end
    end
  
    # Returns one-dimensional absolute distance between cell and target
    # Returns a number to compare distances between cells and the target
    def heuristic_heuristic(cell)
      (grid.target.x - cell.x).abs + (grid.target.y - cell.y).abs
    end
  
    # Calculates the path between the target and star for the heuristic search
    # Only called when the heuristic search finds the target
    def heuristic_calc_path
      # Start from the target
      endpoint = grid.target
      # And the cell it came from
      next_endpoint = heuristic.came_from[endpoint]
      while endpoint and next_endpoint
        # Draw a path between these two cells and store it
        path = get_path_between(endpoint, next_endpoint)
        heuristic.path << path
        # And get the next pair of cells
        endpoint = next_endpoint
        next_endpoint = heuristic.came_from[endpoint]
        # Continue till there are no more cells
      end
    end
  
    # Returns a list of adjacent cells
    # Used to determine what the next cells to be added to the frontier are
    def adjacent_neighbors(cell)
      neighbors = []
  
      # Gets all the valid neighbors into the array
      # From southern neighbor, clockwise
      neighbors << [cell.x    , cell.y - 1] unless cell.y == 0
      neighbors << [cell.x - 1, cell.y    ] unless cell.x == 0
      neighbors << [cell.x    , cell.y + 1] unless cell.y == grid.height - 1
      neighbors << [cell.x + 1, cell.y    ] unless cell.x == grid.width - 1
  
      neighbors
    end
  
    # Finds the vertical and horizontal distance of a cell from the star
    # and returns the larger value
    # This method is used to have a zigzag pattern in the rendered path
    # A cell that is [5, 5] from the star,
    # is explored before over a cell that is [0, 7] away.
    # So, if possible, the search tries to go diagonal (zigzag) first
    def proximity_to_star(cell)
      distance_x = (grid.star.x - cell.x).abs
      distance_y = (grid.star.y - cell.y).abs
  
      if distance_x > distance_y
        return distance_x
      else
        return distance_y
      end
    end
  
    # Methods that allow code to be more concise. Subdivides args.state, which is where all variables are stored.
    def grid
      state.grid
    end
  
    def buttons
      state.buttons
    end
  
    def slider
      state.slider
    end
  
    def bfs
      state.bfs
    end
  
    def heuristic
      state.heuristic
    end
  
    # Descriptive aliases for colors
    def default_color
      [221, 212, 213] # Light Brown
    end
  
    def wall_color
      [134, 134, 120] # Camo Green
    end
  
    def visited_color
      [204, 191, 179] # Dark Brown
    end
  
    def frontier_color
      [103, 136, 204] # Blue
    end
  
    def path_color
      [231, 230, 228] # Pastel White
    end
  
    def button_color
      [190, 190, 190] # Gray
    end
  end
  # Method that is called by DragonRuby periodically
  # Used for updating animations and calculations
  def tick args
  
    # Pressing r will reset the application
    if args.inputs.keyboard.key_down.r
      args.gtk.reset
      reset
      return
    end
  
    # Every tick, new args are passed, and the Breadth First Search tick is called
    $heuristic_with_walls ||= Heuristic_With_Walls.new
    $heuristic_with_walls.args = args
    $heuristic_with_walls.tick
  end
  
  
  def reset
    $heuristic_with_walls = nil
  end

#+end_src

*** Path Finding Algorithms - Heuristic With Walls - main.rb
#+begin_src ruby
  # ./samples/13_path_finding_algorithms/07_heuristic_with_walls/app/main.rb
  # This program is inspired by https://www.redblobgames.com/pathfinding/a-star/introduction.html
  # The effectiveness of the Heuristic search algorithm is shown through this demonstration.
  # Notice that both searches find the shortest path
  # The heuristic search, however, explores less of the grid, and is therefore faster.
  # The heuristic search prioritizes searching cells that are closer to the target.
  # Make sure to look at the Heuristic with walls program to see some of the downsides of the heuristic algorithm.
  
  class Heuristic
    attr_gtk
  
    def tick
      defaults
      render
      input
      # If animation is playing, and max steps have not been reached
      # Move the search a step forward
      if state.play && state.current_step < state.max_steps
        # Variable that tells the program what step to recalculate up to
        state.current_step += 1
        move_searches_one_step_forward
      end
    end
  
    def defaults
      # Variables to edit the size and appearance of the grid
      # Freely customizable to user's liking
      grid.width     ||= 15
      grid.height    ||= 15
      grid.cell_size ||= 40
      grid.rect      ||= [0, 0, grid.width, grid.height]
  
      grid.star      ||= [0, 2]
      grid.target    ||= [14, 12]
      grid.walls     ||= {
        [2, 2] => true,
        [3, 2] => true,
        [4, 2] => true,
        [5, 2] => true,
        [6, 2] => true,
        [7, 2] => true,
        [8, 2] => true,
        [9, 2] => true,
        [10, 2] => true,
        [11, 2] => true,
        [12, 2] => true,
        [12, 3] => true,
        [12, 4] => true,
        [12, 5] => true,
        [12, 6] => true,
        [12, 7] => true,
        [12, 8] => true,
        [12, 9] => true,
        [12, 10] => true,
        [12, 11] => true,
        [12, 12] => true,
        [2, 12] => true,
        [3, 12] => true,
        [4, 12] => true,
        [5, 12] => true,
        [6, 12] => true,
        [7, 12] => true,
        [8, 12] => true,
        [9, 12] => true,
        [10, 12] => true,
        [11, 12] => true,
        [12, 12] => true
      }
      # There are no hills in the Heuristic Search Demo
  
      # What the user is currently editing on the grid
      # We store this value, because we want to remember the value even when
      # the user's cursor is no longer over what they're interacting with, but
      # they are still clicking down on the mouse.
      state.user_input ||= :none
  
      # These variables allow the breadth first search to take place
      # Came_from is a hash with a key of a cell and a value of the cell that was expanded from to find the key.
      # Used to prevent searching cells that have already been found
      # and to trace a path from the target back to the starting point.
      # Frontier is an array of cells to expand the search from.
      # The search is over when there are no more cells to search from.
      # Path stores the path from the target to the star, once the target has been found
      # It prevents calculating the path every tick.
      bfs.came_from  ||= {}
      bfs.frontier   ||= []
      bfs.path       ||= []
  
      heuristic.came_from ||= {}
      heuristic.frontier  ||= []
      heuristic.path      ||= []
  
      # Stores which step of the animation is being rendered
      # When the user moves the star or messes with the walls,
      # the searches are recalculated up to this step
  
      # Unless the current step has a value
      unless state.current_step
        # Set the current step to 10
        state.current_step = 10
        # And calculate the searches up to step 10
        recalculate_searches
      end
  
      # At some step the animation will end,
      # and further steps won't change anything (the whole grid will be explored)
      # This step is roughly the grid's width * height
      # When anim_steps equals max_steps no more calculations will occur
      # and the slider will be at the end
      state.max_steps = grid.width * grid.height
  
      # Whether the animation should play or not
      # If true, every tick moves anim_steps forward one
      # Pressing the stepwise animation buttons will pause the animation
      # An if statement instead of the ||= operator is used for assigning a boolean value.
      # The || operator does not differentiate between nil and false.
      if state.play == nil
        state.play = false
      end
  
      # Store the rects of the buttons that control the animation
      # They are here for user customization
      # Editing these might require recentering the text inside them
      # Those values can be found in the render_button methods
      buttons.left   = [470, 600, 50, 50]
      buttons.center = [520, 600, 200, 50]
      buttons.right  = [720, 600, 50, 50]
  
      # The variables below are related to the slider
      # They allow the user to customize them
      # They also give a central location for the render and input methods to get
      # information from
      # x & y are the coordinates of the leftmost part of the slider line
      slider.x = 440
      slider.y = 675
      # This is the width of the line
      slider.w = 360
      # This is the offset for the circle
      # Allows the center of the circle to be on the line,
      # as opposed to the upper right corner
      slider.offset = 20
      # This is the spacing between each of the notches on the slider
      # Notches are places where the circle can rest on the slider line
      # There needs to be a notch for each step before the maximum number of steps
      slider.spacing = slider.w.to_f / state.max_steps.to_f
    end
  
    # All methods with render draw stuff on the screen
    # UI has buttons, the slider, and labels
    # The search specific rendering occurs in the respective methods
    def render
      render_ui
      render_bfs
      render_heuristic
    end
  
    def render_ui
      render_buttons
      render_slider
      render_labels
    end
  
    def render_buttons
      render_left_button
      render_center_button
      render_right_button
    end
  
    def render_bfs
      render_bfs_grid
      render_bfs_star
      render_bfs_target
      render_bfs_visited
      render_bfs_walls
      render_bfs_frontier
      render_bfs_path
    end
  
    def render_heuristic
      render_heuristic_grid
      render_heuristic_star
      render_heuristic_target
      render_heuristic_visited
      render_heuristic_walls
      render_heuristic_frontier
      render_heuristic_path
    end
  
    # This method handles user input every tick
    def input
      # Check and handle button input
      input_buttons
  
      # If the mouse was lifted this tick
      if inputs.mouse.up
        # Set current input to none
        state.user_input = :none
      end
  
      # If the mouse was clicked this tick
      if inputs.mouse.down
        # Determine what the user is editing and appropriately edit the state.user_input variable
        determine_input
      end
  
      # Process user input based on user_input variable and current mouse position
      process_input
    end
  
    # Determines what the user is editing
    # This method is called when the mouse is clicked down
    def determine_input
      if mouse_over_slider?
        state.user_input = :slider
      # If the mouse is over the star in the first grid
      elsif bfs_mouse_over_star?
        # The user is editing the star from the first grid
        state.user_input = :bfs_star
      # If the mouse is over the star in the second grid
      elsif heuristic_mouse_over_star?
        # The user is editing the star from the second grid
        state.user_input = :heuristic_star
      # If the mouse is over the target in the first grid
      elsif bfs_mouse_over_target?
        # The user is editing the target from the first grid
        state.user_input = :bfs_target
      # If the mouse is over the target in the second grid
      elsif heuristic_mouse_over_target?
        # The user is editing the target from the second grid
        state.user_input = :heuristic_target
      # If the mouse is over a wall in the first grid
      elsif bfs_mouse_over_wall?
        # The user is removing a wall from the first grid
        state.user_input = :bfs_remove_wall
      # If the mouse is over a wall in the second grid
      elsif heuristic_mouse_over_wall?
        # The user is removing a wall from the second grid
        state.user_input = :heuristic_remove_wall
      # If the mouse is over the first grid
      elsif bfs_mouse_over_grid?
        # The user is adding a wall from the first grid
        state.user_input = :bfs_add_wall
      # If the mouse is over the second grid
      elsif heuristic_mouse_over_grid?
        # The user is adding a wall from the second grid
        state.user_input = :heuristic_add_wall
      end
    end
  
    # Processes click and drag based on what the user is currently dragging
    def process_input
      if state.user_input == :slider
        process_input_slider
      elsif state.user_input == :bfs_star
        process_input_bfs_star
      elsif state.user_input == :heuristic_star
        process_input_heuristic_star
      elsif state.user_input == :bfs_target
        process_input_bfs_target
      elsif state.user_input == :heuristic_target
        process_input_heuristic_target
      elsif state.user_input == :bfs_remove_wall
        process_input_bfs_remove_wall
      elsif state.user_input == :heuristic_remove_wall
        process_input_heuristic_remove_wall
      elsif state.user_input == :bfs_add_wall
        process_input_bfs_add_wall
      elsif state.user_input == :heuristic_add_wall
        process_input_heuristic_add_wall
      end
    end
  
    def render_slider
      # Using primitives hides the line under the white circle of the slider
      # Draws the line
      outputs.primitives << [slider.x, slider.y, slider.x + slider.w, slider.y].line
      # The circle needs to be offset so that the center of the circle
      # overlaps the line instead of the upper right corner of the circle
      # The circle's x value is also moved based on the current seach step
      circle_x = (slider.x - slider.offset) + (state.current_step * slider.spacing)
      circle_y = (slider.y - slider.offset)
      circle_rect = [circle_x, circle_y, 37, 37]
      outputs.primitives << [circle_rect, 'circle-white.png'].sprite
    end
  
    def render_labels
      outputs.labels << [205, 625, "Breadth First Search"]
      outputs.labels << [820, 625, "Heuristic Best-First Search"]
    end
  
    def render_left_button
      # Draws the button_color button, and a black border
      # The border separates the buttons visually
      outputs.solids  << [buttons.left, button_color]
      outputs.borders << [buttons.left]
  
      # Renders an explanatory label in the center of the button
      # Explains to the user what the button does
      # If the button size is changed, the label might need to be edited as well
      # to keep the label in the center of the button
      label_x = buttons.left.x + 20
      label_y = buttons.left.y + 35
      outputs.labels  << [label_x, label_y, "<"]
    end
  
    def render_center_button
      # Draws the button_color button, and a black border
      # The border separates the buttons visually
      outputs.solids  << [buttons.center, button_color]
      outputs.borders << [buttons.center]
  
      # Renders an explanatory label in the center of the button
      # Explains to the user what the button does
      # If the button size is changed, the label might need to be edited as well
      # to keep the label in the center of the button
      label_x    = buttons.center.x + 37
      label_y    = buttons.center.y + 35
      label_text = state.play ? "Pause Animation" : "Play Animation"
      outputs.labels << [label_x, label_y, label_text]
    end
  
    def render_right_button
      # Draws the button_color button, and a black border
      # The border separates the buttons visually
      outputs.solids  << [buttons.right, button_color]
      outputs.borders << [buttons.right]
  
      # Renders an explanatory label in the center of the button
      # Explains to the user what the button does
      label_x = buttons.right.x + 20
      label_y = buttons.right.y + 35
      outputs.labels  << [label_x, label_y, ">"]
    end
  
    def render_bfs_grid
      # A large rect the size of the grid
      outputs.solids << [bfs_scale_up(grid.rect), default_color]
  
      # The vertical grid lines
      for x in 0..grid.width
        outputs.lines << bfs_vertical_line(x)
      end
  
      # The horizontal grid lines
      for y in 0..grid.height
        outputs.lines << bfs_horizontal_line(y)
      end
    end
  
    def render_heuristic_grid
      # A large rect the size of the grid
      outputs.solids << [heuristic_scale_up(grid.rect), default_color]
  
      # The vertical grid lines
      for x in 0..grid.width
        outputs.lines << heuristic_vertical_line(x)
      end
  
      # The horizontal grid lines
      for y in 0..grid.height
        outputs.lines << heuristic_horizontal_line(y)
      end
    end
  
    # Returns a vertical line for a column of the first grid
    def bfs_vertical_line column
      bfs_scale_up([column, 0, column, grid.height])
    end
  
    # Returns a horizontal line for a column of the first grid
    def bfs_horizontal_line row
      bfs_scale_up([0, row, grid.width, row])
    end
  
    # Returns a vertical line for a column of the second grid
    def heuristic_vertical_line column
      bfs_scale_up([column + grid.width + 1, 0, column + grid.width + 1, grid.height])
    end
  
    # Returns a horizontal line for a column of the second grid
    def heuristic_horizontal_line row
      bfs_scale_up([grid.width + 1, row, grid.width + grid.width + 1, row])
    end
  
    # Renders the star on the first grid
    def render_bfs_star
      outputs.sprites << [bfs_scale_up(grid.star), 'star.png']
    end
  
    # Renders the star on the second grid
    def render_heuristic_star
      outputs.sprites << [heuristic_scale_up(grid.star), 'star.png']
    end
  
    # Renders the target on the first grid
    def render_bfs_target
      outputs.sprites << [bfs_scale_up(grid.target), 'target.png']
    end
  
    # Renders the target on the second grid
    def render_heuristic_target
      outputs.sprites << [heuristic_scale_up(grid.target), 'target.png']
    end
  
    # Renders the walls on the first grid
    def render_bfs_walls
      grid.walls.each_key do | wall |
        outputs.solids << [bfs_scale_up(wall), wall_color]
      end
    end
  
    # Renders the walls on the second grid
    def render_heuristic_walls
      grid.walls.each_key do | wall |
        outputs.solids << [heuristic_scale_up(wall), wall_color]
      end
    end
  
    # Renders the visited cells on the first grid
    def render_bfs_visited
      bfs.came_from.each_key do | visited_cell |
        outputs.solids << [bfs_scale_up(visited_cell), visited_color]
      end
    end
  
    # Renders the visited cells on the second grid
    def render_heuristic_visited
      heuristic.came_from.each_key do | visited_cell |
        outputs.solids << [heuristic_scale_up(visited_cell), visited_color]
      end
    end
  
    # Renders the frontier cells on the first grid
    def render_bfs_frontier
      bfs.frontier.each do | frontier_cell |
        outputs.solids << [bfs_scale_up(frontier_cell), frontier_color, 200]
      end
    end
  
    # Renders the frontier cells on the second grid
    def render_heuristic_frontier
      heuristic.frontier.each do | frontier_cell |
        outputs.solids << [heuristic_scale_up(frontier_cell), frontier_color, 200]
      end
    end
  
    # Renders the path found by the breadth first search on the first grid
    def render_bfs_path
      bfs.path.each do | path |
        outputs.solids << [bfs_scale_up(path), path_color]
      end
    end
  
    # Renders the path found by the heuristic search on the second grid
    def render_heuristic_path
      heuristic.path.each do | path |
        outputs.solids << [heuristic_scale_up(path), path_color]
      end
    end
  
    # Returns the rect for the path between two cells based on their relative positions
    def get_path_between(cell_one, cell_two)
      path = []
  
      # If cell one is above cell two
      if cell_one.x == cell_two.x and cell_one.y > cell_two.y
        # Path starts from the center of cell two and moves upward to the center of cell one
        path = [cell_two.x + 0.3, cell_two.y + 0.3, 0.4, 1.4]
      # If cell one is below cell two
      elsif cell_one.x == cell_two.x and cell_one.y < cell_two.y
        # Path starts from the center of cell one and moves upward to the center of cell two
        path = [cell_one.x + 0.3, cell_one.y + 0.3, 0.4, 1.4]
      # If cell one is to the left of cell two
      elsif cell_one.x > cell_two.x and cell_one.y == cell_two.y
        # Path starts from the center of cell two and moves rightward to the center of cell one
        path = [cell_two.x + 0.3, cell_two.y + 0.3, 1.4, 0.4]
      # If cell one is to the right of cell two
      elsif cell_one.x < cell_two.x and cell_one.y == cell_two.y
        # Path starts from the center of cell one and moves rightward to the center of cell two
        path = [cell_one.x + 0.3, cell_one.y + 0.3, 1.4, 0.4]
      end
  
      path
    end
  
    # In code, the cells are represented as 1x1 rectangles
    # When drawn, the cells are larger than 1x1 rectangles
    # This method is used to scale up cells, and lines
    # Objects are scaled up according to the grid.cell_size variable
    # This allows for easy customization of the visual scale of the grid
    # This method scales up cells for the first grid
    def bfs_scale_up(cell)
      # Prevents the original value of cell from being edited
      cell = cell.clone
  
      # If cell is just an x and y coordinate
      if cell.size == 2
        # Add a width and height of 1
        cell << 1
        cell << 1
      end
  
      # Scale all the values up
      cell.map! { |value| value * grid.cell_size }
  
      # Returns the scaled up cell
      cell
    end
  
    # Translates the given cell grid.width + 1 to the right and then scales up
    # Used to draw cells for the second grid
    # This method does not work for lines,
    # so separate methods exist for the grid lines
    def heuristic_scale_up(cell)
      # Prevents the original value of cell from being edited
      cell = cell.clone
      # Translates the cell to the second grid equivalent
      cell.x += grid.width + 1
      # Proceeds as if scaling up for the first grid
      bfs_scale_up(cell)
    end
  
    # Checks and handles input for the buttons
    # Called when the mouse is lifted
    def input_buttons
      input_left_button
      input_center_button
      input_right_button
    end
  
    # Checks if the previous step button is clicked
    # If it is, it pauses the animation and moves the search one step backward
    def input_left_button
      if left_button_clicked?
        state.play = false
        state.current_step -= 1
        recalculate_searches
      end
    end
  
    # Controls the play/pause button
    # Inverses whether the animation is playing or not when clicked
    def input_center_button
      if center_button_clicked? || inputs.keyboard.key_down.space
        state.play = !state.play
      end
    end
  
    # Checks if the next step button is clicked
    # If it is, it pauses the animation and moves the search one step forward
    def input_right_button
      if right_button_clicked?
        state.play = false
        state.current_step += 1
        move_searches_one_step_forward
      end
    end
  
    # These methods detect when the buttons are clicked
    def left_button_clicked?
      inputs.mouse.point.inside_rect?(buttons.left) && inputs.mouse.up
    end
  
    def center_button_clicked?
      inputs.mouse.point.inside_rect?(buttons.center) && inputs.mouse.up
    end
  
    def right_button_clicked?
      inputs.mouse.point.inside_rect?(buttons.right) && inputs.mouse.up
    end
  
  
    # Signal that the user is going to be moving the slider
    # Is the mouse over the circle of the slider?
    def mouse_over_slider?
      circle_x = (slider.x - slider.offset) + (state.current_step * slider.spacing)
      circle_y = (slider.y - slider.offset)
      circle_rect = [circle_x, circle_y, 37, 37]
      inputs.mouse.point.inside_rect?(circle_rect)
    end
  
    # Signal that the user is going to be moving the star from the first grid
    def bfs_mouse_over_star?
      inputs.mouse.point.inside_rect?(bfs_scale_up(grid.star))
    end
  
    # Signal that the user is going to be moving the star from the second grid
    def heuristic_mouse_over_star?
      inputs.mouse.point.inside_rect?(heuristic_scale_up(grid.star))
    end
  
    # Signal that the user is going to be moving the target from the first grid
    def bfs_mouse_over_target?
      inputs.mouse.point.inside_rect?(bfs_scale_up(grid.target))
    end
  
    # Signal that the user is going to be moving the target from the second grid
    def heuristic_mouse_over_target?
      inputs.mouse.point.inside_rect?(heuristic_scale_up(grid.target))
    end
  
    # Signal that the user is going to be removing walls from the first grid
    def bfs_mouse_over_wall?
      grid.walls.each_key do | wall |
        return true if inputs.mouse.point.inside_rect?(bfs_scale_up(wall))
      end
  
      false
    end
  
    # Signal that the user is going to be removing walls from the second grid
    def heuristic_mouse_over_wall?
      grid.walls.each_key do | wall |
        return true if inputs.mouse.point.inside_rect?(heuristic_scale_up(wall))
      end
  
      false
    end
  
    # Signal that the user is going to be adding walls from the first grid
    def bfs_mouse_over_grid?
      inputs.mouse.point.inside_rect?(bfs_scale_up(grid.rect))
    end
  
    # Signal that the user is going to be adding walls from the second grid
    def heuristic_mouse_over_grid?
      inputs.mouse.point.inside_rect?(heuristic_scale_up(grid.rect))
    end
  
    # This method is called when the user is editing the slider
    # It pauses the animation and moves the white circle to the closest integer point
    # on the slider
    # Changes the step of the search to be animated
    def process_input_slider
      state.play = false
      mouse_x = inputs.mouse.point.x
  
      # Bounds the mouse_x to the closest x value on the slider line
      mouse_x = slider.x if mouse_x < slider.x
      mouse_x = slider.x + slider.w if mouse_x > slider.x + slider.w
  
      # Sets the current search step to the one represented by the mouse x value
      # The slider's circle moves due to the render_slider method using anim_steps
      state.current_step = ((mouse_x - slider.x) / slider.spacing).to_i
  
      recalculate_searches
    end
  
    # Moves the star to the cell closest to the mouse in the first grid
    # Only resets the search if the star changes position
    # Called whenever the user is editing the star (puts mouse down on star)
    def process_input_bfs_star
      old_star = grid.star.clone
      unless bfs_cell_closest_to_mouse == grid.target
        grid.star = bfs_cell_closest_to_mouse
      end
      unless old_star == grid.star
        recalculate_searches
      end
    end
  
    # Moves the star to the cell closest to the mouse in the second grid
    # Only resets the search if the star changes position
    # Called whenever the user is editing the star (puts mouse down on star)
    def process_input_heuristic_star
      old_star = grid.star.clone
      unless heuristic_cell_closest_to_mouse == grid.target
        grid.star = heuristic_cell_closest_to_mouse
      end
      unless old_star == grid.star
        recalculate_searches
      end
    end
  
    # Moves the target to the grid closest to the mouse in the first grid
    # Only recalculate_searchess the search if the target changes position
    # Called whenever the user is editing the target (puts mouse down on target)
    def process_input_bfs_target
      old_target = grid.target.clone
      unless bfs_cell_closest_to_mouse == grid.star
        grid.target = bfs_cell_closest_to_mouse
      end
      unless old_target == grid.target
        recalculate_searches
      end
    end
  
    # Moves the target to the cell closest to the mouse in the second grid
    # Only recalculate_searchess the search if the target changes position
    # Called whenever the user is editing the target (puts mouse down on target)
    def process_input_heuristic_target
      old_target = grid.target.clone
      unless heuristic_cell_closest_to_mouse == grid.star
        grid.target = heuristic_cell_closest_to_mouse
      end
      unless old_target == grid.target
        recalculate_searches
      end
    end
  
    # Removes walls in the first grid that are under the cursor
    def process_input_bfs_remove_wall
      # The mouse needs to be inside the grid, because we only want to remove walls
      # the cursor is directly over
      # Recalculations should only occur when a wall is actually deleted
      if bfs_mouse_over_grid?
        if grid.walls.has_key?(bfs_cell_closest_to_mouse)
          grid.walls.delete(bfs_cell_closest_to_mouse)
          recalculate_searches
        end
      end
    end
  
    # Removes walls in the second grid that are under the cursor
    def process_input_heuristic_remove_wall
      # The mouse needs to be inside the grid, because we only want to remove walls
      # the cursor is directly over
      # Recalculations should only occur when a wall is actually deleted
      if heuristic_mouse_over_grid?
        if grid.walls.has_key?(heuristic_cell_closest_to_mouse)
          grid.walls.delete(heuristic_cell_closest_to_mouse)
          recalculate_searches
        end
      end
    end
    # Adds a wall in the first grid in the cell the mouse is over
    def process_input_bfs_add_wall
      if bfs_mouse_over_grid?
        unless grid.walls.has_key?(bfs_cell_closest_to_mouse)
          grid.walls[bfs_cell_closest_to_mouse] = true
          recalculate_searches
        end
      end
    end
  
    # Adds a wall in the second grid in the cell the mouse is over
    def process_input_heuristic_add_wall
      if heuristic_mouse_over_grid?
        unless grid.walls.has_key?(heuristic_cell_closest_to_mouse)
          grid.walls[heuristic_cell_closest_to_mouse] = true
          recalculate_searches
        end
      end
    end
  
    # When the user grabs the star and puts their cursor to the far right
    # and moves up and down, the star is supposed to move along the grid as well
    # Finding the cell closest to the mouse helps with this
    def bfs_cell_closest_to_mouse
      # Closest cell to the mouse in the first grid
      x = (inputs.mouse.point.x / grid.cell_size).to_i
      y = (inputs.mouse.point.y / grid.cell_size).to_i
      # Bound x and y to the grid
      x = grid.width - 1 if x > grid.width - 1
      y = grid.height - 1 if y > grid.height - 1
      # Return closest cell
      [x, y]
    end
  
    # When the user grabs the star and puts their cursor to the far right
    # and moves up and down, the star is supposed to move along the grid as well
    # Finding the cell closest to the mouse in the second grid helps with this
    def heuristic_cell_closest_to_mouse
      # Closest cell grid to the mouse in the second
      x = (inputs.mouse.point.x / grid.cell_size).to_i
      y = (inputs.mouse.point.y / grid.cell_size).to_i
      # Translate the cell to the first grid
      x -= grid.width + 1
      # Bound x and y to the first grid
      x = 0 if x < 0
      y = 0 if y < 0
      x = grid.width - 1 if x > grid.width - 1
      y = grid.height - 1 if y > grid.height - 1
      # Return closest cell
      [x, y]
    end
  
    def recalculate_searches
      # Reset the searches
      bfs.came_from    = {}
      bfs.frontier     = []
      bfs.path         = []
      heuristic.came_from = {}
      heuristic.frontier  = []
      heuristic.path      = []
  
      # Move the searches forward to the current step
      state.current_step.times { move_searches_one_step_forward }
    end
  
    def move_searches_one_step_forward
      bfs_one_step_forward
      heuristic_one_step_forward
    end
  
    def bfs_one_step_forward
      return if bfs.came_from.has_key?(grid.target)
  
      # Only runs at the beginning of the search as setup.
      if bfs.came_from.empty?
        bfs.frontier << grid.star
        bfs.came_from[grid.star] = nil
      end
  
      # A step in the search
      unless bfs.frontier.empty?
        # Takes the next frontier cell
        new_frontier = bfs.frontier.shift
        # For each of its neighbors
        adjacent_neighbors(new_frontier).each do |neighbor|
          # That have not been visited and are not walls
          unless bfs.came_from.has_key?(neighbor) || grid.walls.has_key?(neighbor)
            # Add them to the frontier and mark them as visited
            bfs.frontier << neighbor
            bfs.came_from[neighbor] = new_frontier
          end
        end
      end
  
      # Sort the frontier so that cells that are in a zigzag pattern are prioritized over those in an line
      # Comment this line and let a path generate to see the difference
      bfs.frontier = bfs.frontier.sort_by {| cell | proximity_to_star(cell) }
  
      # If the search found the target
      if bfs.came_from.has_key?(grid.target)
        # Calculate the path between the target and star
        bfs_calc_path
      end
    end
  
    # Calculates the path between the target and star for the breadth first search
    # Only called when the breadth first search finds the target
    def bfs_calc_path
      # Start from the target
      endpoint = grid.target
      # And the cell it came from
      next_endpoint = bfs.came_from[endpoint]
      while endpoint and next_endpoint
        # Draw a path between these two cells and store it
        path = get_path_between(endpoint, next_endpoint)
        bfs.path << path
        # And get the next pair of cells
        endpoint = next_endpoint
        next_endpoint = bfs.came_from[endpoint]
        # Continue till there are no more cells
      end
    end
  
    # Moves the heuristic search forward one step
    # Can be called from tick while the animation is playing
    # Can also be called when recalculating the searches after the user edited the grid
    def heuristic_one_step_forward
      # Stop the search if the target has been found
      return if heuristic.came_from.has_key?(grid.target)
  
      # If the search has not begun
      if heuristic.came_from.empty?
        # Setup the search to begin from the star
        heuristic.frontier << grid.star
        heuristic.came_from[grid.star] = nil
      end
  
      # One step in the heuristic search
  
      # Unless there are no more cells to explore from
      unless heuristic.frontier.empty?
        # Get the next cell to explore from
        new_frontier = heuristic.frontier.shift
        # For each of its neighbors
        adjacent_neighbors(new_frontier).each do |neighbor|
          # That have not been visited and are not walls
          unless heuristic.came_from.has_key?(neighbor) || grid.walls.has_key?(neighbor)
            # Add them to the frontier and mark them as visited
            heuristic.frontier << neighbor
            heuristic.came_from[neighbor] = new_frontier
          end
        end
      end
  
      # Sort the frontier so that cells that are in a zigzag pattern are prioritized over those in an line
      heuristic.frontier = heuristic.frontier.sort_by {| cell | proximity_to_star(cell) }
      # Sort the frontier so cells that are close to the target are then prioritized
      heuristic.frontier = heuristic.frontier.sort_by {| cell | heuristic_heuristic(cell)  }
  
      # If the search found the target
      if heuristic.came_from.has_key?(grid.target)
        # Calculate the path between the target and star
        heuristic_calc_path
      end
    end
  
    # Returns one-dimensional absolute distance between cell and target
    # Returns a number to compare distances between cells and the target
    def heuristic_heuristic(cell)
      (grid.target.x - cell.x).abs + (grid.target.y - cell.y).abs
    end
  
    # Calculates the path between the target and star for the heuristic search
    # Only called when the heuristic search finds the target
    def heuristic_calc_path
      # Start from the target
      endpoint = grid.target
      # And the cell it came from
      next_endpoint = heuristic.came_from[endpoint]
      while endpoint and next_endpoint
        # Draw a path between these two cells and store it
        path = get_path_between(endpoint, next_endpoint)
        heuristic.path << path
        # And get the next pair of cells
        endpoint = next_endpoint
        next_endpoint = heuristic.came_from[endpoint]
        # Continue till there are no more cells
      end
    end
  
    # Returns a list of adjacent cells
    # Used to determine what the next cells to be added to the frontier are
    def adjacent_neighbors(cell)
      neighbors = []
  
      # Gets all the valid neighbors into the array
      # From southern neighbor, clockwise
      neighbors << [cell.x    , cell.y - 1] unless cell.y == 0
      neighbors << [cell.x - 1, cell.y    ] unless cell.x == 0
      neighbors << [cell.x    , cell.y + 1] unless cell.y == grid.height - 1
      neighbors << [cell.x + 1, cell.y    ] unless cell.x == grid.width - 1
  
      neighbors
    end
  
    # Finds the vertical and horizontal distance of a cell from the star
    # and returns the larger value
    # This method is used to have a zigzag pattern in the rendered path
    # A cell that is [5, 5] from the star,
    # is explored before over a cell that is [0, 7] away.
    # So, if possible, the search tries to go diagonal (zigzag) first
    def proximity_to_star(cell)
      distance_x = (grid.star.x - cell.x).abs
      distance_y = (grid.star.y - cell.y).abs
  
      if distance_x > distance_y
        return distance_x
      else
        return distance_y
      end
    end
  
    # Methods that allow code to be more concise. Subdivides args.state, which is where all variables are stored.
    def grid
      state.grid
    end
  
    def buttons
      state.buttons
    end
  
    def slider
      state.slider
    end
  
    def bfs
      state.bfs
    end
  
    def heuristic
      state.heuristic
    end
  
    # Descriptive aliases for colors
    def default_color
      [221, 212, 213] # Light Brown
    end
  
    def wall_color
      [134, 134, 120] # Camo Green
    end
  
    def visited_color
      [204, 191, 179] # Dark Brown
    end
  
    def frontier_color
      [103, 136, 204] # Blue
    end
  
    def path_color
      [231, 230, 228] # Pastel White
    end
  
    def button_color
      [190, 190, 190] # Gray
    end
  end
  # Method that is called by DragonRuby periodically
  # Used for updating animations and calculations
  def tick args
  
    # Pressing r will reset the application
    if args.inputs.keyboard.key_down.r
      args.gtk.reset
      reset
      return
    end
  
    # Every tick, new args are passed, and the Breadth First Search tick is called
    $heuristic ||= Heuristic.new
    $heuristic.args = args
    $heuristic.tick
  end
  
  
  def reset
    $heuristic = nil
  end

#+end_src

*** Path Finding Algorithms - A Star - main.rb
#+begin_src ruby
  # ./samples/13_path_finding_algorithms/08_a_star/app/main.rb
  # This program is inspired by https://www.redblobgames.com/pathfinding/a-star/introduction.html
  
  # The A* Search works by incorporating both the distance from the starting point
  # and the distance from the target in its heurisitic.
  
  # It tends to find the correct (shortest) path even when the Greedy Best-First Search does not,
  # and it explores less of the grid, and is therefore faster, than Dijkstra's Search.
  
  class A_Star_Algorithm
    attr_gtk
  
    def tick
      defaults
      render
      input
  
      if dijkstra.came_from.empty?
        calc_searches
      end
    end
  
    def defaults
      # Variables to edit the size and appearance of the grid
      # Freely customizable to user's liking
      grid.width     ||= 15
      grid.height    ||= 15
      grid.cell_size ||= 27
      grid.rect      ||= [0, 0, grid.width, grid.height]
  
      grid.star      ||= [0, 2]
      grid.target    ||= [11, 13]
      grid.walls     ||= {
        [2, 2] => true,
        [3, 2] => true,
        [4, 2] => true,
        [5, 2] => true,
        [6, 2] => true,
        [7, 2] => true,
        [8, 2] => true,
        [9, 2] => true,
        [10, 2] => true,
        [11, 2] => true,
        [12, 2] => true,
        [12, 3] => true,
        [12, 4] => true,
        [12, 5] => true,
        [12, 6] => true,
        [12, 7] => true,
        [12, 8] => true,
        [12, 9] => true,
        [12, 10] => true,
        [12, 11] => true,
        [12, 12] => true,
        [5, 12] => true,
        [6, 12] => true,
        [7, 12] => true,
        [8, 12] => true,
        [9, 12] => true,
        [10, 12] => true,
        [11, 12] => true,
        [12, 12] => true
      }
  
      # What the user is currently editing on the grid
      # We store this value, because we want to remember the value even when
      # the user's cursor is no longer over what they're interacting with, but
      # they are still clicking down on the mouse.
      state.user_input ||= :none
  
      # These variables allow the breadth first search to take place
      # Came_from is a hash with a key of a cell and a value of the cell that was expanded from to find the key.
      # Used to prevent searching cells that have already been found
      # and to trace a path from the target back to the starting point.
      # Frontier is an array of cells to expand the search from.
      # The search is over when there are no more cells to search from.
      # Path stores the path from the target to the star, once the target has been found
      # It prevents calculating the path every tick.
      dijkstra.came_from   ||= {}
      dijkstra.cost_so_far ||= {}
      dijkstra.frontier    ||= []
      dijkstra.path        ||= []
  
      greedy.came_from ||= {}
      greedy.frontier  ||= []
      greedy.path      ||= []
  
      a_star.frontier  ||= []
      a_star.came_from ||= {}
      a_star.path      ||= []
    end
  
    # All methods with render draw stuff on the screen
    # UI has buttons, the slider, and labels
    # The search specific rendering occurs in the respective methods
    def render
      render_labels
      render_dijkstra
      render_greedy
      render_a_star
    end
  
    def render_labels
      outputs.labels << [150, 450, "Dijkstra's"]
      outputs.labels << [550, 450, "Greedy Best-First"]
      outputs.labels << [1025, 450, "A* Search"]
    end
  
    def render_dijkstra
      render_dijkstra_grid
      render_dijkstra_star
      render_dijkstra_target
      render_dijkstra_visited
      render_dijkstra_walls
      render_dijkstra_path
    end
  
    def render_greedy
      render_greedy_grid
      render_greedy_star
      render_greedy_target
      render_greedy_visited
      render_greedy_walls
      render_greedy_path
    end
  
    def render_a_star
      render_a_star_grid
      render_a_star_star
      render_a_star_target
      render_a_star_visited
      render_a_star_walls
      render_a_star_path
    end
  
    # This method handles user input every tick
    def input
      # If the mouse was lifted this tick
      if inputs.mouse.up
        # Set current input to none
        state.user_input = :none
      end
  
      # If the mouse was clicked this tick
      if inputs.mouse.down
        # Determine what the user is editing and appropriately edit the state.user_input variable
        determine_input
      end
  
      # Process user input based on user_input variable and current mouse position
      process_input
    end
  
    # Determines what the user is editing
    # This method is called when the mouse is clicked down
    def determine_input
      # If the mouse is over the star in the first grid
      if dijkstra_mouse_over_star?
        # The user is editing the star from the first grid
        state.user_input = :dijkstra_star
      # If the mouse is over the star in the second grid
      elsif greedy_mouse_over_star?
        # The user is editing the star from the second grid
        state.user_input = :greedy_star
      # If the mouse is over the star in the third grid
      elsif a_star_mouse_over_star?
        # The user is editing the star from the third grid
        state.user_input = :a_star_star
      # If the mouse is over the target in the first grid
      elsif dijkstra_mouse_over_target?
        # The user is editing the target from the first grid
        state.user_input = :dijkstra_target
      # If the mouse is over the target in the second grid
      elsif greedy_mouse_over_target?
        # The user is editing the target from the second grid
        state.user_input = :greedy_target
      # If the mouse is over the target in the third grid
      elsif a_star_mouse_over_target?
        # The user is editing the target from the third grid
        state.user_input = :a_star_target
      # If the mouse is over a wall in the first grid
      elsif dijkstra_mouse_over_wall?
        # The user is removing a wall from the first grid
        state.user_input = :dijkstra_remove_wall
      # If the mouse is over a wall in the second grid
      elsif greedy_mouse_over_wall?
        # The user is removing a wall from the second grid
        state.user_input = :greedy_remove_wall
      # If the mouse is over a wall in the third grid
      elsif a_star_mouse_over_wall?
        # The user is removing a wall from the third grid
        state.user_input = :a_star_remove_wall
      # If the mouse is over the first grid
      elsif dijkstra_mouse_over_grid?
        # The user is adding a wall from the first grid
        state.user_input = :dijkstra_add_wall
      # If the mouse is over the second grid
      elsif greedy_mouse_over_grid?
        # The user is adding a wall from the second grid
        state.user_input = :greedy_add_wall
      # If the mouse is over the third grid
      elsif a_star_mouse_over_grid?
        # The user is adding a wall from the third grid
        state.user_input = :a_star_add_wall
      end
    end
  
    # Processes click and drag based on what the user is currently dragging
    def process_input
      if state.user_input == :dijkstra_star
        process_input_dijkstra_star
      elsif state.user_input == :greedy_star
        process_input_greedy_star
      elsif state.user_input == :a_star_star
        process_input_a_star_star
      elsif state.user_input == :dijkstra_target
        process_input_dijkstra_target
      elsif state.user_input == :greedy_target
        process_input_greedy_target
      elsif state.user_input == :a_star_target
        process_input_a_star_target
      elsif state.user_input == :dijkstra_remove_wall
        process_input_dijkstra_remove_wall
      elsif state.user_input == :greedy_remove_wall
        process_input_greedy_remove_wall
      elsif state.user_input == :a_star_remove_wall
        process_input_a_star_remove_wall
      elsif state.user_input == :dijkstra_add_wall
        process_input_dijkstra_add_wall
      elsif state.user_input == :greedy_add_wall
        process_input_greedy_add_wall
      elsif state.user_input == :a_star_add_wall
        process_input_a_star_add_wall
      end
    end
  
    def render_dijkstra_grid
      # A large rect the size of the grid
      outputs.solids << [dijkstra_scale_up(grid.rect), default_color]
  
      # The vertical grid lines
      for x in 0..grid.width
        outputs.lines << dijkstra_vertical_line(x)
      end
  
      # The horizontal grid lines
      for y in 0..grid.height
        outputs.lines << dijkstra_horizontal_line(y)
      end
    end
  
    def render_greedy_grid
      # A large rect the size of the grid
      outputs.solids << [greedy_scale_up(grid.rect), default_color]
  
      # The vertical grid lines
      for x in 0..grid.width
        outputs.lines << greedy_vertical_line(x)
      end
  
      # The horizontal grid lines
      for y in 0..grid.height
        outputs.lines << greedy_horizontal_line(y)
      end
    end
  
    def render_a_star_grid
      # A large rect the size of the grid
      outputs.solids << [a_star_scale_up(grid.rect), default_color]
  
      # The vertical grid lines
      for x in 0..grid.width
        outputs.lines << a_star_vertical_line(x)
      end
  
      # The horizontal grid lines
      for y in 0..grid.height
        outputs.lines << a_star_horizontal_line(y)
      end
    end
  
    # Returns a vertical line for a column of the first grid
    def dijkstra_vertical_line column
      dijkstra_scale_up([column, 0, column, grid.height])
    end
  
    # Returns a horizontal line for a column of the first grid
    def dijkstra_horizontal_line row
      dijkstra_scale_up([0, row, grid.width, row])
    end
  
    # Returns a vertical line for a column of the second grid
    def greedy_vertical_line column
      dijkstra_scale_up([column + grid.width + 1, 0, column + grid.width + 1, grid.height])
    end
  
    # Returns a horizontal line for a column of the second grid
    def greedy_horizontal_line row
      dijkstra_scale_up([grid.width + 1, row, grid.width + grid.width + 1, row])
    end
  
    # Returns a vertical line for a column of the third grid
    def a_star_vertical_line column
      dijkstra_scale_up([column + (grid.width * 2) + 2, 0, column + (grid.width * 2) + 2, grid.height])
    end
  
    # Returns a horizontal line for a column of the third grid
    def a_star_horizontal_line row
      dijkstra_scale_up([(grid.width * 2) + 2, row, (grid.width * 2) + grid.width + 2, row])
    end
  
    # Renders the star on the first grid
    def render_dijkstra_star
      outputs.sprites << [dijkstra_scale_up(grid.star), 'star.png']
    end
  
    # Renders the star on the second grid
    def render_greedy_star
      outputs.sprites << [greedy_scale_up(grid.star), 'star.png']
    end
  
    # Renders the star on the third grid
    def render_a_star_star
      outputs.sprites << [a_star_scale_up(grid.star), 'star.png']
    end
  
    # Renders the target on the first grid
    def render_dijkstra_target
      outputs.sprites << [dijkstra_scale_up(grid.target), 'target.png']
    end
  
    # Renders the target on the second grid
    def render_greedy_target
      outputs.sprites << [greedy_scale_up(grid.target), 'target.png']
    end
  
    # Renders the target on the third grid
    def render_a_star_target
      outputs.sprites << [a_star_scale_up(grid.target), 'target.png']
    end
  
    # Renders the walls on the first grid
    def render_dijkstra_walls
      grid.walls.each_key do | wall |
        outputs.solids << [dijkstra_scale_up(wall), wall_color]
      end
    end
  
    # Renders the walls on the second grid
    def render_greedy_walls
      grid.walls.each_key do | wall |
        outputs.solids << [greedy_scale_up(wall), wall_color]
      end
    end
  
    # Renders the walls on the third grid
    def render_a_star_walls
      grid.walls.each_key do | wall |
        outputs.solids << [a_star_scale_up(wall), wall_color]
      end
    end
  
    # Renders the visited cells on the first grid
    def render_dijkstra_visited
      dijkstra.came_from.each_key do | visited_cell |
        outputs.solids << [dijkstra_scale_up(visited_cell), visited_color]
      end
    end
  
    # Renders the visited cells on the second grid
    def render_greedy_visited
      greedy.came_from.each_key do | visited_cell |
        outputs.solids << [greedy_scale_up(visited_cell), visited_color]
      end
    end
  
    # Renders the visited cells on the third grid
    def render_a_star_visited
      a_star.came_from.each_key do | visited_cell |
        outputs.solids << [a_star_scale_up(visited_cell), visited_color]
      end
    end
  
    # Renders the path found by the breadth first search on the first grid
    def render_dijkstra_path
      dijkstra.path.each do | path |
        outputs.solids << [dijkstra_scale_up(path), path_color]
      end
    end
  
    # Renders the path found by the greedy search on the second grid
    def render_greedy_path
      greedy.path.each do | path |
        outputs.solids << [greedy_scale_up(path), path_color]
      end
    end
  
    # Renders the path found by the a_star search on the third grid
    def render_a_star_path
      a_star.path.each do | path |
        outputs.solids << [a_star_scale_up(path), path_color]
      end
    end
  
    # Returns the rect for the path between two cells based on their relative positions
    def get_path_between(cell_one, cell_two)
      path = []
  
      # If cell one is above cell two
      if cell_one.x == cell_two.x and cell_one.y > cell_two.y
        # Path starts from the center of cell two and moves upward to the center of cell one
        path = [cell_two.x + 0.3, cell_two.y + 0.3, 0.4, 1.4]
      # If cell one is below cell two
      elsif cell_one.x == cell_two.x and cell_one.y < cell_two.y
        # Path starts from the center of cell one and moves upward to the center of cell two
        path = [cell_one.x + 0.3, cell_one.y + 0.3, 0.4, 1.4]
      # If cell one is to the left of cell two
      elsif cell_one.x > cell_two.x and cell_one.y == cell_two.y
        # Path starts from the center of cell two and moves rightward to the center of cell one
        path = [cell_two.x + 0.3, cell_two.y + 0.3, 1.4, 0.4]
      # If cell one is to the right of cell two
      elsif cell_one.x < cell_two.x and cell_one.y == cell_two.y
        # Path starts from the center of cell one and moves rightward to the center of cell two
        path = [cell_one.x + 0.3, cell_one.y + 0.3, 1.4, 0.4]
      end
  
      path
    end
  
    # In code, the cells are represented as 1x1 rectangles
    # When drawn, the cells are larger than 1x1 rectangles
    # This method is used to scale up cells, and lines
    # Objects are scaled up according to the grid.cell_size variable
    # This allows for easy customization of the visual scale of the grid
    # This method scales up cells for the first grid
    def dijkstra_scale_up(cell)
      # Prevents the original value of cell from being edited
      cell = cell.clone
  
      # If cell is just an x and y coordinate
      if cell.size == 2
        # Add a width and height of 1
        cell << 1
        cell << 1
      end
  
      # Scale all the values up
      cell.map! { |value| value * grid.cell_size }
  
      # Returns the scaled up cell
      cell
    end
  
    # Translates the given cell grid.width + 1 to the right and then scales up
    # Used to draw cells for the second grid
    # This method does not work for lines,
    # so separate methods exist for the grid lines
    def greedy_scale_up(cell)
      # Prevents the original value of cell from being edited
      cell = cell.clone
      # Translates the cell to the second grid equivalent
      cell.x += grid.width + 1
      # Proceeds as if scaling up for the first grid
      dijkstra_scale_up(cell)
    end
  
    # Translates the given cell (grid.width + 1) * 2 to the right and then scales up
    # Used to draw cells for the third grid
    # This method does not work for lines,
    # so separate methods exist for the grid lines
    def a_star_scale_up(cell)
      # Prevents the original value of cell from being edited
      cell = cell.clone
      # Translates the cell to the second grid equivalent
      cell.x += grid.width + 1
      # Translates the cell to the third grid equivalent
      cell.x += grid.width + 1
      # Proceeds as if scaling up for the first grid
      dijkstra_scale_up(cell)
    end
  
    # Signal that the user is going to be moving the star from the first grid
    def dijkstra_mouse_over_star?
      inputs.mouse.point.inside_rect?(dijkstra_scale_up(grid.star))
    end
  
    # Signal that the user is going to be moving the star from the second grid
    def greedy_mouse_over_star?
      inputs.mouse.point.inside_rect?(greedy_scale_up(grid.star))
    end
  
    # Signal that the user is going to be moving the star from the third grid
    def a_star_mouse_over_star?
      inputs.mouse.point.inside_rect?(a_star_scale_up(grid.star))
    end
  
    # Signal that the user is going to be moving the target from the first grid
    def dijkstra_mouse_over_target?
      inputs.mouse.point.inside_rect?(dijkstra_scale_up(grid.target))
    end
  
    # Signal that the user is going to be moving the target from the second grid
    def greedy_mouse_over_target?
      inputs.mouse.point.inside_rect?(greedy_scale_up(grid.target))
    end
  
    # Signal that the user is going to be moving the target from the third grid
    def a_star_mouse_over_target?
      inputs.mouse.point.inside_rect?(a_star_scale_up(grid.target))
    end
  
    # Signal that the user is going to be removing walls from the first grid
    def dijkstra_mouse_over_wall?
      grid.walls.each_key do | wall |
        return true if inputs.mouse.point.inside_rect?(dijkstra_scale_up(wall))
      end
  
      false
    end
  
    # Signal that the user is going to be removing walls from the second grid
    def greedy_mouse_over_wall?
      grid.walls.each_key do | wall |
        return true if inputs.mouse.point.inside_rect?(greedy_scale_up(wall))
      end
  
      false
    end
  
    # Signal that the user is going to be removing walls from the third grid
    def a_star_mouse_over_wall?
      grid.walls.each_key do | wall |
        return true if inputs.mouse.point.inside_rect?(a_star_scale_up(wall))
      end
  
      false
    end
  
    # Signal that the user is going to be adding walls from the first grid
    def dijkstra_mouse_over_grid?
      inputs.mouse.point.inside_rect?(dijkstra_scale_up(grid.rect))
    end
  
    # Signal that the user is going to be adding walls from the second grid
    def greedy_mouse_over_grid?
      inputs.mouse.point.inside_rect?(greedy_scale_up(grid.rect))
    end
  
    # Signal that the user is going to be adding walls from the third grid
    def a_star_mouse_over_grid?
      inputs.mouse.point.inside_rect?(a_star_scale_up(grid.rect))
    end
  
    # Moves the star to the cell closest to the mouse in the first grid
    # Only resets the search if the star changes position
    # Called whenever the user is editing the star (puts mouse down on star)
    def process_input_dijkstra_star
      old_star = grid.star.clone
      unless dijkstra_cell_closest_to_mouse == grid.target
        grid.star = dijkstra_cell_closest_to_mouse
      end
      unless old_star == grid.star
        reset_searches
      end
    end
  
    # Moves the star to the cell closest to the mouse in the second grid
    # Only resets the search if the star changes position
    # Called whenever the user is editing the star (puts mouse down on star)
    def process_input_greedy_star
      old_star = grid.star.clone
      unless greedy_cell_closest_to_mouse == grid.target
        grid.star = greedy_cell_closest_to_mouse
      end
      unless old_star == grid.star
        reset_searches
      end
    end
  
    # Moves the star to the cell closest to the mouse in the third grid
    # Only resets the search if the star changes position
    # Called whenever the user is editing the star (puts mouse down on star)
    def process_input_a_star_star
      old_star = grid.star.clone
      unless a_star_cell_closest_to_mouse == grid.target
        grid.star = a_star_cell_closest_to_mouse
      end
      unless old_star == grid.star
        reset_searches
      end
    end
  
    # Moves the target to the grid closest to the mouse in the first grid
    # Only reset_searchess the search if the target changes position
    # Called whenever the user is editing the target (puts mouse down on target)
    def process_input_dijkstra_target
      old_target = grid.target.clone
      unless dijkstra_cell_closest_to_mouse == grid.star
        grid.target = dijkstra_cell_closest_to_mouse
      end
      unless old_target == grid.target
        reset_searches
      end
    end
  
    # Moves the target to the cell closest to the mouse in the second grid
    # Only reset_searchess the search if the target changes position
    # Called whenever the user is editing the target (puts mouse down on target)
    def process_input_greedy_target
      old_target = grid.target.clone
      unless greedy_cell_closest_to_mouse == grid.star
        grid.target = greedy_cell_closest_to_mouse
      end
      unless old_target == grid.target
        reset_searches
      end
    end
  
    # Moves the target to the cell closest to the mouse in the third grid
    # Only reset_searchess the search if the target changes position
    # Called whenever the user is editing the target (puts mouse down on target)
    def process_input_a_star_target
      old_target = grid.target.clone
      unless a_star_cell_closest_to_mouse == grid.star
        grid.target = a_star_cell_closest_to_mouse
      end
      unless old_target == grid.target
        reset_searches
      end
    end
  
    # Removes walls in the first grid that are under the cursor
    def process_input_dijkstra_remove_wall
      # The mouse needs to be inside the grid, because we only want to remove walls
      # the cursor is directly over
      # Recalculations should only occur when a wall is actually deleted
      if dijkstra_mouse_over_grid?
        if grid.walls.has_key?(dijkstra_cell_closest_to_mouse)
          grid.walls.delete(dijkstra_cell_closest_to_mouse)
          reset_searches
        end
      end
    end
  
    # Removes walls in the second grid that are under the cursor
    def process_input_greedy_remove_wall
      # The mouse needs to be inside the grid, because we only want to remove walls
      # the cursor is directly over
      # Recalculations should only occur when a wall is actually deleted
      if greedy_mouse_over_grid?
        if grid.walls.has_key?(greedy_cell_closest_to_mouse)
          grid.walls.delete(greedy_cell_closest_to_mouse)
          reset_searches
        end
      end
    end
  
    # Removes walls in the third grid that are under the cursor
    def process_input_a_star_remove_wall
      # The mouse needs to be inside the grid, because we only want to remove walls
      # the cursor is directly over
      # Recalculations should only occur when a wall is actually deleted
      if a_star_mouse_over_grid?
        if grid.walls.has_key?(a_star_cell_closest_to_mouse)
          grid.walls.delete(a_star_cell_closest_to_mouse)
          reset_searches
        end
      end
    end
  
    # Adds a wall in the first grid in the cell the mouse is over
    def process_input_dijkstra_add_wall
      if dijkstra_mouse_over_grid?
        unless grid.walls.has_key?(dijkstra_cell_closest_to_mouse)
          grid.walls[dijkstra_cell_closest_to_mouse] = true
          reset_searches
        end
      end
    end
  
    # Adds a wall in the second grid in the cell the mouse is over
    def process_input_greedy_add_wall
      if greedy_mouse_over_grid?
        unless grid.walls.has_key?(greedy_cell_closest_to_mouse)
          grid.walls[greedy_cell_closest_to_mouse] = true
          reset_searches
        end
      end
    end
  
    # Adds a wall in the third grid in the cell the mouse is over
    def process_input_a_star_add_wall
      if a_star_mouse_over_grid?
        unless grid.walls.has_key?(a_star_cell_closest_to_mouse)
          grid.walls[a_star_cell_closest_to_mouse] = true
          reset_searches
        end
      end
    end
  
    # When the user grabs the star and puts their cursor to the far right
    # and moves up and down, the star is supposed to move along the grid as well
    # Finding the cell closest to the mouse helps with this
    def dijkstra_cell_closest_to_mouse
      # Closest cell to the mouse in the first grid
      x = (inputs.mouse.point.x / grid.cell_size).to_i
      y = (inputs.mouse.point.y / grid.cell_size).to_i
      # Bound x and y to the grid
      x = grid.width - 1 if x > grid.width - 1
      y = grid.height - 1 if y > grid.height - 1
      # Return closest cell
      [x, y]
    end
  
    # When the user grabs the star and puts their cursor to the far right
    # and moves up and down, the star is supposed to move along the grid as well
    # Finding the cell closest to the mouse in the second grid helps with this
    def greedy_cell_closest_to_mouse
      # Closest cell grid to the mouse in the second
      x = (inputs.mouse.point.x / grid.cell_size).to_i
      y = (inputs.mouse.point.y / grid.cell_size).to_i
      # Translate the cell to the first grid
      x -= grid.width + 1
      # Bound x and y to the first grid
      x = 0 if x < 0
      y = 0 if y < 0
      x = grid.width - 1 if x > grid.width - 1
      y = grid.height - 1 if y > grid.height - 1
      # Return closest cell
      [x, y]
    end
  
    # When the user grabs the star and puts their cursor to the far right
    # and moves up and down, the star is supposed to move along the grid as well
    # Finding the cell closest to the mouse in the third grid helps with this
    def a_star_cell_closest_to_mouse
      # Closest cell grid to the mouse in the second
      x = (inputs.mouse.point.x / grid.cell_size).to_i
      y = (inputs.mouse.point.y / grid.cell_size).to_i
      # Translate the cell to the first grid
      x -= (grid.width + 1) * 2
      # Bound x and y to the first grid
      x = 0 if x < 0
      y = 0 if y < 0
      x = grid.width - 1 if x > grid.width - 1
      y = grid.height - 1 if y > grid.height - 1
      # Return closest cell
      [x, y]
    end
  
    def reset_searches
      # Reset the searches
      dijkstra.came_from      = {}
      dijkstra.cost_so_far    = {}
      dijkstra.frontier       = []
      dijkstra.path           = []
  
      greedy.came_from = {}
      greedy.frontier  = []
      greedy.path      = []
      a_star.came_from = {}
      a_star.frontier  = []
      a_star.path      = []
    end
  
    def calc_searches
      calc_dijkstra
      calc_greedy
      calc_a_star
      # Move the searches forward to the current step
      # state.current_step.times { move_searches_one_step_forward }
    end
  
    def calc_dijkstra
      # Sets up the search to begin from the star
      dijkstra.frontier << grid.star
      dijkstra.came_from[grid.star] = nil
      dijkstra.cost_so_far[grid.star] = 0
  
      # Until the target is found or there are no more cells to explore from
      until dijkstra.came_from.has_key?(grid.target) or dijkstra.frontier.empty?
        # Take the next frontier cell. The first element is the cell, the second is the priority.
        new_frontier = dijkstra.frontier.shift#[0]
        # For each of its neighbors
        adjacent_neighbors(new_frontier).each do | neighbor |
          # That have not been visited and are not walls
          unless dijkstra.came_from.has_key?(neighbor) or grid.walls.has_key?(neighbor)
            # Add them to the frontier and mark them as visited
            dijkstra.frontier << neighbor
            dijkstra.came_from[neighbor] = new_frontier
            dijkstra.cost_so_far[neighbor] = dijkstra.cost_so_far[new_frontier] + 1
          end
        end
  
        # Sort the frontier so that cells that are in a zigzag pattern are prioritized over those in an line
        # Comment this line and let a path generate to see the difference
        dijkstra.frontier = dijkstra.frontier.sort_by {| cell | proximity_to_star(cell) }
        dijkstra.frontier = dijkstra.frontier.sort_by {| cell | dijkstra.cost_so_far[cell] }
      end
  
  
      # If the search found the target
      if dijkstra.came_from.has_key?(grid.target)
        # Calculate the path between the target and star
        dijkstra_calc_path
      end
    end
  
    def calc_greedy
      # Sets up the search to begin from the star
      greedy.frontier << grid.star
      greedy.came_from[grid.star] = nil
  
      # Until the target is found or there are no more cells to explore from
      until greedy.came_from.has_key?(grid.target) or greedy.frontier.empty?
        # Take the next frontier cell
        new_frontier = greedy.frontier.shift
        # For each of its neighbors
        adjacent_neighbors(new_frontier).each do | neighbor |
          # That have not been visited and are not walls
          unless greedy.came_from.has_key?(neighbor) or grid.walls.has_key?(neighbor)
            # Add them to the frontier and mark them as visited
            greedy.frontier << neighbor
            greedy.came_from[neighbor] = new_frontier
          end
        end
        # Sort the frontier so that cells that are in a zigzag pattern are prioritized over those in an line
        # Comment this line and let a path generate to see the difference
        greedy.frontier = greedy.frontier.sort_by {| cell | proximity_to_star(cell) }
        # Sort the frontier so cells that are close to the target are then prioritized
        greedy.frontier = greedy.frontier.sort_by {| cell | greedy_heuristic(cell)  }
      end
  
  
      # If the search found the target
      if greedy.came_from.has_key?(grid.target)
        # Calculate the path between the target and star
        greedy_calc_path
      end
    end
  
    def calc_a_star
      # Setup the search to start from the star
      a_star.came_from[grid.star] = nil
      a_star.cost_so_far[grid.star] = 0
      a_star.frontier << grid.star
  
      # Until there are no more cells to explore from or the search has found the target
      until a_star.frontier.empty? or a_star.came_from.has_key?(grid.target)
        # Get the next cell to expand from
        current_frontier = a_star.frontier.shift
  
        # For each of that cells neighbors
        adjacent_neighbors(current_frontier).each do | neighbor |
          # That have not been visited and are not walls
          unless a_star.came_from.has_key?(neighbor) or grid.walls.has_key?(neighbor)
            # Add them to the frontier and mark them as visited
            a_star.frontier << neighbor
            a_star.came_from[neighbor] = current_frontier
            a_star.cost_so_far[neighbor] = a_star.cost_so_far[current_frontier] + 1
          end
        end
  
        # Sort the frontier so that cells that are in a zigzag pattern are prioritized over those in an line
        # Comment this line and let a path generate to see the difference
        a_star.frontier = a_star.frontier.sort_by {| cell | proximity_to_star(cell) }
        a_star.frontier = a_star.frontier.sort_by {| cell | a_star.cost_so_far[cell] + greedy_heuristic(cell) }
      end
  
      # If the search found the target
      if a_star.came_from.has_key?(grid.target)
        # Calculate the path between the target and star
        a_star_calc_path
      end
    end
  
    # Calculates the path between the target and star for the breadth first search
    # Only called when the breadth first search finds the target
    def dijkstra_calc_path
      # Start from the target
      endpoint = grid.target
      # And the cell it came from
      next_endpoint = dijkstra.came_from[endpoint]
      while endpoint and next_endpoint
        # Draw a path between these two cells and store it
        path = get_path_between(endpoint, next_endpoint)
        dijkstra.path << path
        # And get the next pair of cells
        endpoint = next_endpoint
        next_endpoint = dijkstra.came_from[endpoint]
        # Continue till there are no more cells
      end
    end
  
    # Returns one-dimensional absolute distance between cell and target
    # Returns a number to compare distances between cells and the target
    def greedy_heuristic(cell)
      (grid.target.x - cell.x).abs + (grid.target.y - cell.y).abs
    end
  
    # Calculates the path between the target and star for the greedy search
    # Only called when the greedy search finds the target
    def greedy_calc_path
      # Start from the target
      endpoint = grid.target
      # And the cell it came from
      next_endpoint = greedy.came_from[endpoint]
      while endpoint and next_endpoint
        # Draw a path between these two cells and store it
        path = get_path_between(endpoint, next_endpoint)
        greedy.path << path
        # And get the next pair of cells
        endpoint = next_endpoint
        next_endpoint = greedy.came_from[endpoint]
        # Continue till there are no more cells
      end
    end
  
    # Calculates the path between the target and star for the a_star search
    # Only called when the a_star search finds the target
    def a_star_calc_path
      # Start from the target
      endpoint = grid.target
      # And the cell it came from
      next_endpoint = a_star.came_from[endpoint]
  
      while endpoint and next_endpoint
        # Draw a path between these two cells and store it
        path = get_path_between(endpoint, next_endpoint)
        a_star.path << path
        # And get the next pair of cells
        endpoint = next_endpoint
        next_endpoint = a_star.came_from[endpoint]
        # Continue till there are no more cells
      end
    end
  
    # Returns a list of adjacent cells
    # Used to determine what the next cells to be added to the frontier are
    def adjacent_neighbors(cell)
      neighbors = []
  
      # Gets all the valid neighbors into the array
      # From southern neighbor, clockwise
      neighbors << [cell.x    , cell.y - 1] unless cell.y == 0
      neighbors << [cell.x - 1, cell.y    ] unless cell.x == 0
      neighbors << [cell.x    , cell.y + 1] unless cell.y == grid.height - 1
      neighbors << [cell.x + 1, cell.y    ] unless cell.x == grid.width - 1
  
      neighbors
    end
  
    # Finds the vertical and horizontal distance of a cell from the star
    # and returns the larger value
    # This method is used to have a zigzag pattern in the rendered path
    # A cell that is [5, 5] from the star,
    # is explored before over a cell that is [0, 7] away.
    # So, if possible, the search tries to go diagonal (zigzag) first
    def proximity_to_star(cell)
      distance_x = (grid.star.x - cell.x).abs
      distance_y = (grid.star.y - cell.y).abs
  
      if distance_x > distance_y
        return distance_x
      else
        return distance_y
      end
    end
  
    # Methods that allow code to be more concise. Subdivides args.state, which is where all variables are stored.
    def grid
      state.grid
    end
  
    def dijkstra
      state.dijkstra
    end
  
    def greedy
      state.greedy
    end
  
    def a_star
      state.a_star
    end
  
    # Descriptive aliases for colors
    def default_color
      [221, 212, 213] # Light Brown
    end
  
    def wall_color
      [134, 134, 120] # Camo Green
    end
  
    def visited_color
      [204, 191, 179] # Dark Brown
    end
  
    def path_color
      [231, 230, 228] # Pastel White
    end
  
    def button_color
      [190, 190, 190] # Gray
    end
  end
  
  
  # Method that is called by DragonRuby periodically
  # Used for updating animations and calculations
  def tick args
  
    # Pressing r will reset the application
    if args.inputs.keyboard.key_down.r
      args.gtk.reset
      reset
      return
    end
  
    # Every tick, new args are passed, and the Breadth First Search tick is called
    $a_star_algorithm ||= A_Star_Algorithm.new
    $a_star_algorithm.args = args
    $a_star_algorithm.tick
  end
  
  
  def reset
    $a_star_algorithm = nil
  end

#+end_src

*** Path Finding Algorithms - Tower Defense - main.rb
#+begin_src ruby
  # ./samples/13_path_finding_algorithms/09_tower_defense/app/main.rb
  # An example of some major components in a tower defence game
  # The pathing of the tanks is determined by A* algorithm -- try editing the walls
  
  # The turrets shoot bullets at the closest tank. The bullets are heat-seeking
  
  def tick args
    $gtk.reset if args.inputs.keyboard.key_down.r
    defaults args
    render args
    calc args
  end
  
  def defaults args
    args.outputs.background_color = wall_color
    args.state.grid_size = 5
    args.state.tile_size = 50
    args.state.grid_start ||= [0, 0]
    args.state.grid_goal  ||= [4, 4]
  
    # Try editing these walls to see the path change!
    args.state.walls ||= {
      [0, 4] => true,
      [1, 3] => true,
      [3, 1] => true,
      # [4, 0] => true,
    }
  
    args.state.a_star.frontier ||= []
    args.state.a_star.came_from ||= {}
    args.state.a_star.path ||= []
  
    args.state.tanks ||= []
    args.state.tank_spawn_period ||= 60
    args.state.tank_sprite_path ||= 'sprites/circle/white.png'
    args.state.tank_speed ||= 1
  
    args.state.turret_shoot_period = 10
    # Turrets can be entered as [x, y] but are immediately mapped to hashes
    # Walls are also added where the turrets are to prevent tanks from pathing over them
    args.state.turrets ||= [
      [2, 2]
    ].each { |turret| args.state.walls[turret] = true}.map do |x, y|
      {
        x: x * args.state.tile_size,
        y: y * args.state.tile_size,
        w: args.state.tile_size,
        h: args.state.tile_size,
        path: 'sprites/circle/gray.png',
        range: 100
      }
    end
  
    args.state.bullet_size ||= 25
    args.state.bullets ||= []
    args.state.bullet_path ||= 'sprites/circle/orange.png'
    #
  end
  
  def render args
    render_grid args
    render_a_star args
    args.outputs.sprites << args.state.tanks
    args.outputs.sprites << args.state.turrets
    args.outputs.sprites << args.state.bullets
  end
  
  def render_grid args
    # Draw a square the size and color of the grid
    args.outputs.solids << [
      0,
      0,
      args.state.grid_size * args.state.tile_size,
      args.state.grid_size * args.state.tile_size,
      grid_color
    ]
  
    # Draw lines across the grid to show tiles
    (args.state.grid_size + 1).times do | value |
      render_horizontal_line(args, value)
      render_vertical_line(args, value)
    end
  
    # Render special tiles
    render_tile(args, args.state.grid_start, start_color)
    render_tile(args, args.state.grid_goal, goal_color)
    args.state.walls.keys.each { |wall| render_tile(args, wall, wall_color) }
  end
  
  def render_vertical_line args, x
    args.outputs.lines << [
      x * args.state.tile_size,
      0,
      x * args.state.tile_size,
      args.state.tile_size * args.state.grid_size,
    ]
  end
  
  def render_horizontal_line args, y
    args.outputs.lines << [
      0,
      y * args.state.tile_size,
      args.state.tile_size * args.state.grid_size,
      y * args.state.tile_size,
    ]
  end
  
  def render_tile args, tile, color
    args.outputs.solids << [
      tile.x * args.state.tile_size,
      tile.y * args.state.tile_size,
      args.state.tile_size,
      args.state.tile_size,
      color
    ]
  end
  
  def calc args
    calc_a_star args
    calc_tanks args
    calc_turrets args
    calc_bullets args
  end
  
  def calc_a_star args
    # Only does this one time
    return unless args.state.a_star.path.empty?
  
    # Start the search from the grid start
    args.state.a_star.frontier << args.state.grid_start
    args.state.a_star.came_from[args.state.grid_start] = nil
  
    # Until a path to the goal has been found or there are no more tiles to explore
    until (args.state.a_star.came_from.has_key?(args.state.grid_goal)|| args.state.a_star.frontier.empty?)
      # For the first tile in the frontier
      tile_to_expand_from = args.state.a_star.frontier.shift
      # Add each of its neighbors to the frontier
      neighbors(args, tile_to_expand_from).each do | tile |
        args.state.a_star.frontier << tile
        args.state.a_star.came_from[tile] = tile_to_expand_from
      end
    end
  
    # Stop calculating a path if the goal was never reached
    return unless args.state.a_star.came_from.has_key? args.state.grid_goal
  
    # Fill path by tracing back from the goal
    current_cell = args.state.grid_goal
    while current_cell
      args.state.a_star.path.unshift current_cell
      current_cell = args.state.a_star.came_from[current_cell]
    end
  
    puts "The path has been calculated"
    puts args.state.a_star.path
  end
  
  def calc_tanks args
    spawn_tank args
    move_tanks args
  end
  
  def move_tanks args
    # Remove tanks that have reached the end of their path
    args.state.tanks.reject! { |tank| tank[:a_star].empty? }
  
    # Tanks have an array that has each tile it has to go to in order from a* path
    args.state.tanks.each do | tank |
      destination = tank[:a_star][0]
      # Move the tank towards the destination
      tank[:x] += copy_sign(args.state.tank_speed, ((destination.x * args.state.tile_size) - tank[:x]))
      tank[:y] += copy_sign(args.state.tank_speed, ((destination.y * args.state.tile_size) - tank[:y]))
      # If the tank has reached its destination
      if (destination.x * args.state.tile_size) == tank[:x] and
          (destination.y * args.state.tile_size) == tank[:y]
        # Set the destination to the next point in the path
        tank[:a_star].shift
      end
    end
  end
  
  def calc_turrets args
    return unless args.state.tick_count.mod_zero? args.state.turret_shoot_period
    args.state.turrets.each do | turret |
      # Finds the closest tank
      target = nil
      shortest_distance = turret[:range] + 1
      args.state.tanks.each do | tank |
        distance = distance_between(turret[:x], turret[:y], tank[:x], tank[:y])
        if distance < shortest_distance
          target = tank
          shortest_distance = distance
        end
      end
      # If there is a tank in range, fires a bullet
      if target
        args.state.bullets << {
          x: turret[:x],
          y: turret[:y],
          w: args.state.bullet_size,
          h: args.state.bullet_size,
          path: args.state.bullet_path,
          # Note that this makes it heat-seeking, because target is passed by reference
          # Could do target.clone to make the bullet go to where the tank initially was
          target: target
        }
      end
    end
  end
  
  def calc_bullets args
    # Bullets aim for the center of their targets
    args.state.bullets.each { |bullet| move bullet, center_of(bullet[:target])}
    args.state.bullets.reject! { |b| b.intersect_rect? b[:target] }
  end
  
  def center_of object
    object = object.clone
    object[:x] += 0.5
    object[:y] += 0.5
    object
  end
  
  def render_a_star args
    args.state.a_star.path.map do |tile|
      # Map each x, y coordinate to the center of the tile and scale up
      [(tile.x + 0.5) * args.state.tile_size, (tile.y + 0.5) * args.state.tile_size]
    end.inject do | point_a,  point_b |
      # Render the line between each point
      args.outputs.lines << [point_a.x, point_a.y, point_b.x, point_b.y, a_star_color]
      point_b
    end
  end
  
  # Moves object to target at speed
  def move object, target, speed = 1
    if target.is_a? Hash
      object[:x] += copy_sign(speed, target[:x] - object[:x])
      object[:y] += copy_sign(speed, target[:y] - object[:y])
    else
      object[:x] += copy_sign(speed, target.x - object[:x])
      object[:y] += copy_sign(speed, target.y - object[:y])
    end
  end
  #
  #
  def distance_between a_x, a_y, b_x, b_y
    (((b_x - a_x) ** 2) + ((b_y - a_y) ** 2)) ** 0.5
  end
  
  def copy_sign value, sign
    return 0 if sign == 0
    return value if sign > 0
    -value
  end
  #
  def spawn_tank args
    return unless args.state.tick_count.mod_zero? args.state.tank_spawn_period
    args.state.tanks << {
      x: args.state.grid_start.x,
      y: args.state.grid_start.y,
      w: args.state.tile_size,
      h: args.state.tile_size,
      path: args.state.tank_sprite_path,
      a_star: args.state.a_star.path.clone
    }
  end
  
  def neighbors args, tile
    [[tile.x, tile.y - 1],
     [tile.x, tile.y + 1],
     [tile.x + 1, tile.y],
     [tile.x - 1, tile.y]].reject do | neighbor |
      args.state.a_star.came_from.has_key?(neighbor) or
        tile_out_of_bounds?(args, neighbor) or
        args.state.walls.has_key? neighbor
    end
  end
  
  def tile_out_of_bounds? args, tile
    tile.x < 0 or tile.y < 0 or tile.x >= args.state.grid_size or tile.y >= args.state.grid_size
  end
  
  def grid_color
    [133, 226, 144]
  end
  
  def start_color
    [226, 144, 133]
  end
  
  def goal_color
    [226, 133, 144]
  end
  
  def wall_color
    [133, 144, 226]
  end
  
  def a_star_color
    [0, 0, 255]
  end

#+end_src

*** 14 Vr - Skybox - main.rb
#+begin_src ruby
  # ./samples/14_vr/01_skybox/app/main.rb
  require 'app/tick.rb'
  
  def tick args
    args.gtk.start_server! port: 9001, enable_in_prod: true
    tick_game args
  end

#+end_src

*** 14 Vr - Skybox - tick.rb
#+begin_src ruby
  # ./samples/14_vr/01_skybox/app/tick.rb
  def skybox args, x, y, z, size
    sprite = { a: 128, path: 'sprites/box.png' }
  
    front      = { x: x, y: y, z: z, w: size, h: size, **sprite }
    front_720  = { x: x, y: y, z: z, w: size, h: size * 9.fdiv(16), **sprite }
    back       = { x: x, y: y, z: z + size, w: size, h: size, **sprite }
    bottom     = { x: x, y: y - size.half, z: z + size.half, w: size, h: size, angle_x: 90, **sprite }
    top        = { x: x, y: y + size.half, z: z + size.half, w: size, h: size, angle_x: 90, **sprite }
    left       = { x: x - size.half, y: y, w: size, h: size, z: z + size.half, angle_y: 90, **sprite }
    right      = { x: x + size.half, y: y, w: size, h: size, z: z + size.half, angle_y: 90, **sprite }
  
    args.outputs.sprites << [back,
                             left,
                             top,
                             bottom,
                             right,
                             front,
                             front_720]
  end
  
  def tick_game args
    args.outputs.background_color = [0, 0, 0]
  
    args.state.z     ||= 0
    args.state.scale ||= 0.05
  
    if args.inputs.controller_one.key_down.a
      if args.grid.name == :bottom_left
        args.grid.origin_center!
      else
        args.grid.origin_bottom_left!
      end
    end
  
    args.state.scale += args.inputs.controller_one.right_analog_x_perc * 0.01
    args.state.z += args.inputs.controller_one.right_analog_y_perc * 1.5
  
    args.state.scale = args.state.scale.clamp(0.05, 1.0)
    args.state.z = 0    if args.state.z < 0
    args.state.z = 1280 if args.state.z > 1280
  
    skybox args, 0, 0, args.state.z, 1280 * args.state.scale
  
    render_guides args
  end
  
  def render_guides args
    label_style = { alignment_enum: 1,
                    size_enum: -2,
                    vertical_alignment_enum: 0, r: 255, g: 255, b: 255 }
  
    instructions = [
      "scale: #{args.state.scale.to_sf} (right analog left/right)",
      "z: #{args.state.z.to_sf} (right analog up/down)",
      "origin: :#{args.grid.name} (A button)"
    ]
  
    args.outputs.labels << instructions.map_with_index do |text, i|
      { x: 640,
        y: 100 + ((instructions.length - (i + 1)) * 22),
        z: args.state.z,
        a: 255,
        text: text,
        ** label_style,
        alignment_enum: 1,
        vertical_alignment_enum: 0 }
    end
  
    # lines for scaled box
    size      = 1280 * args.state.scale
    size_16_9 = size * 9.fdiv(16)
  
    args.outputs.primitives << [
      { x: size - 1280, y: size,        z:            0, w: 1280 * 2, r: 128, g: 128, b: 128, a:  64 }.line!,
      { x: size - 1280, y: size,        z: args.state.z, w: 1280 * 2, r: 128, g: 128, b: 128, a: 255 }.line!,
  
      { x: size - 1280, y: size_16_9,   z:            0, w: 1280 * 2, r: 128, g: 128, b: 128, a:  64 }.line!,
      { x: size - 1280, y: size_16_9,   z: args.state.z, w: 1280 * 2, r: 128, g: 128, b: 128, a: 255 }.line!,
  
      { x: size,        y: size - 1280, z:            0, h: 1280 * 2, r: 128, g: 128, b: 128, a:  64 }.line!,
      { x: size,        y: size - 1280, z: args.state.z, h: 1280 * 2, r: 128, g: 128, b: 128, a: 255 }.line!,
  
      { x: size,        y: size,        z: args.state.z, size_enum: -2,
        vertical_alignment_enum: 0,
        text: "#{size.to_sf}, #{size.to_sf}, #{args.state.z.to_sf}",
        r: 255, g: 255, b: 255, a: 255 }.label!,
  
      { x: size,        y: size_16_9,   z: args.state.z, size_enum: -2,
        vertical_alignment_enum: 0,
        text: "#{size.to_sf}, #{size_16_9.to_sf}, #{args.state.z.to_sf}",
        r: 255, g: 255, b: 255, a: 255 }.label!,
    ]
  
    xs = [
      { description: "left",   x:    0, alignment_enum: 0 },
      { description: "center", x:  640, alignment_enum: 1 },
      { description: "right",  x: 1280, alignment_enum: 2 },
    ]
  
    ys = [
      { description: "bottom",        y:    0, vertical_alignment_enum: 0 },
      { description: "center",        y:  640, vertical_alignment_enum: 1 },
      { description: "center (720p)", y:  360, vertical_alignment_enum: 1 },
      { description: "top",           y: 1280, vertical_alignment_enum: 2 },
      { description: "top (720p)",    y:  720, vertical_alignment_enum: 2 },
    ]
  
    args.outputs.primitives << xs.product(ys).map do |(xdef, ydef)|
      [
        { x: xdef.x,
          y: ydef.y,
          z: args.state.z,
          text: "#{xdef.x.to_sf}, #{ydef.y.to_sf} #{args.state.z}",
          **label_style,
          alignment_enum: xdef.alignment_enum,
          vertical_alignment_enum: ydef.vertical_alignment_enum
        },
        { x: xdef.x,
          y: ydef.y - 20,
          z: args.state.z,
          text: "#{ydef.description}, #{xdef.description}",
          **label_style,
          alignment_enum: xdef.alignment_enum,
          vertical_alignment_enum: ydef.vertical_alignment_enum
        }
      ]
    end
  
    args.outputs.primitives << xs.product(ys).map do |(xdef, ydef)|
      [
        {
          x: xdef.x - 1280,
          y: ydef.y,
          w: 1280 * 2,
          a: 64,
          r: 128, g: 128, b: 128
        }.line!,
        {
          x: xdef.x,
          y: ydef.y - 720,
          h: 720 * 2,
          a: 64,
          r: 128, g: 128, b: 128
        }.line!,
      ].map do |p|
        [
          p.merge(z:            0, a:  64),
          p.merge(z: args.state.z, a: 255)
        ]
      end
    end
  end
  
  $gtk.reset

#+end_src

*** 14 Vr - Top Down Rpg - main.rb
#+begin_src ruby
  # ./samples/14_vr/02_top_down_rpg/app/main.rb
  require 'app/tick.rb'
  
  def tick args
    args.gtk.start_server! port: 9001, enable_in_prod: true
    tick_game args
  end

#+end_src

*** 14 Vr - Top Down Rpg - tick.rb
#+begin_src ruby
  # ./samples/14_vr/02_top_down_rpg/app/tick.rb
  class Game
    attr_gtk
  
    def tick
      outputs.background_color = [0, 0, 0]
      args.state.tile_size     = 80
      args.state.player_speed  = 4
      args.state.player      ||= tile(args, 7, 3, 0, 128, 180)
      generate_map args
  
      # adds walls, goal, and player to args.outputs.solids so they appear on screen
      args.outputs.solids << args.state.goal
      args.outputs.solids << args.state.walls
      args.outputs.solids << args.state.player
  
      args.outputs.solids << args.state.walls.map { |s| s.to_hash.merge(z: 2, g: 80) }
      args.outputs.solids << args.state.walls.map { |s| s.to_hash.merge(z: 6, g: 255, a: 128) }
  
      # if player's box intersects with goal, a label is output onto the screen
      if args.state.player.intersect_rect? args.state.goal
        args.outputs.labels << { x: 640,
                                 y: 360,
                                 z: 10,
                                 text: "YOU'RE A GOD DAMN WIZARD, HARRY.",
                                 size_enum: 10,
                                 alignment_enum: 1,
                                 vertical_alignment_enum: 1,
                                 r: 255,
                                 g: 255,
                                 b: 255 }
      end
  
      move_player args, -1,  0 if args.inputs.keyboard.left  || args.inputs.controller_one.left # x position decreases by 1 if left key is pressed
      move_player args,  1,  0 if args.inputs.keyboard.right || args.inputs.controller_one.right # x position increases by 1 if right key is pressed
      move_player args,  0,  1 if args.inputs.keyboard.up    || args.inputs.controller_one.down # y position increases by 1 if up is pressed
      move_player args,  0, -1 if args.inputs.keyboard.down  || args.inputs.controller_one.up # y position decreases by 1 if down is pressed
    end
  
    # Sets position, size, and color of the tile
    def tile args, x, y, *color
      [x * args.state.tile_size, # sets definition for array using method parameters
       y * args.state.tile_size, # multiplying by tile_size sets x and y to correct position using pixel values
       args.state.tile_size,
       args.state.tile_size,
       *color]
    end
  
    # Creates map by adding tiles to the wall, as well as a goal (that the player needs to reach)
    def generate_map args
      return if args.state.area
  
      # Creates the area of the map. There are 9 rows running horizontally across the screen
      # and 16 columns running vertically on the screen. Any spot with a "1" is not
      # open for the player to move into (and is green), and any spot with a "0" is available
      # for the player to move in.
      args.state.area = [
        [1, 1, 1, 1, 1, 1, 1, 0, 0, 1, 1, 1, 1, 1, 1, 1,],
        [1, 1, 1, 2, 1, 1, 1, 0, 0, 1, 1, 1, 1, 1, 1, 1,], # the "2" represents the goal
        [1, 1, 1, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1,],
        [1, 1, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1,],
        [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,],
        [1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1,],
        [1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1,],
        [1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,],
        [1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1 ],
      ].reverse # reverses the order of the area collection
  
      # By reversing the order, the way that the area appears above is how it appears
      # on the screen in the game. If we did not reverse, the map would appear inverted.
  
      #The wall starts off with no tiles.
      args.state.walls = []
  
      # If v is 1, a green tile is added to args.state.walls.
      # If v is 2, a black tile is created as the goal.
      args.state.area.map_2d do |y, x, v|
        if    v == 1
          args.state.walls << tile(args, x, y, 0, 255, 0) # green tile
        elsif v == 2 # notice there is only one "2" above because there is only one single goal
          args.state.goal   = tile(args, x, y, 180,  0, 0) # black tile
        end
      end
    end
  
    # Allows the player to move their box around the screen
    def move_player args, *vector
      box = args.state.player.shift_rect(vector) # box is able to move at an angle
  
      # If the player's box hits a wall, it is not able to move further in that direction
      return if args.state.walls
                  .any_intersect_rect?(box)
  
      # Player's box is able to move at angles (not just the four general directions) fast
      args.state.player =
        args.state.player
          .shift_rect(vector.x * args.state.player_speed, # if we don't multiply by speed, then
                      vector.y * args.state.player_speed) # the box will move extremely slow
    end
  end
  
  $game = Game.new
  
  def tick_game args
    $game.args = args
    $game.tick
  end
  
  $gtk.reset

#+end_src

*** 14 Vr - Space Invaders - main.rb
#+begin_src ruby
  # ./samples/14_vr/03_space_invaders/app/main.rb
  require 'app/tick.rb'
  
  def tick args
    args.gtk.start_server! port: 9001, enable_in_prod: true
    tick_game args
  end

#+end_src

*** 14 Vr - Space Invaders - tick.rb
#+begin_src ruby
  # ./samples/14_vr/03_space_invaders/app/tick.rb
  class Game
    attr_gtk
  
    def tick
      grid.origin_center!
      defaults
      outputs.background_color = [0, 0, 0]
      args.outputs.sprites << state.enemies.map { |e| enemy_prefab e }
  
      if gtk.platform? :macos
        args.outputs.borders << hmap(x: -150,
                                     y: -220,
                                     w: 300, h: 130, r: 255, g: 255, b: 255)
      end
    end
  
    def defaults
      state.enemy_sprite_size = 64
      state.row_size = 16
      state.max_rows = 20
      state.enemies ||= 160.map_with_index do |i|
        x = i % 16
        y = i.idiv 16
        hmap row: y, col: x
      end
    end
  
    def enemy_prefab enemy
      if enemy.row > state.max_rows
        raise "#{enemy}"
      end
      relative_row = enemy.row + 1
      z = 50 - relative_row * 10
      x = (enemy.col * state.enemy_sprite_size) - (state.enemy_sprite_size * state.row_size).idiv(2)
      enemy_sprite(x, enemy.row * 10, z, enemy)
    end
  
    def enemy_sprite x, y, z, meta
      index = 0.frame_index count: 2, hold_for: 50, repeat: true
      pmap(x: x, y: y, z: z, w: state.enemy_sprite_size, h: state.enemy_sprite_size, path: 'sprites/enemy.png', source_x: 128 * index, source_y: 0, source_w: 128, source_h: 128, meta: meta)
    end
  
    def pmap opts
      if gtk.platform? :macos
        if opts.z >= 60
          return nil
        elsif (opts.z * 8) > 1000
          return nil
        elsif opts.z <= 60
          scale = (1000 - opts.z * 8).fdiv(1000)
          hscale = 0.5 * scale ** 6
          vscale = scale
          w = (state.enemy_sprite_size * 0.5) * hscale
          h = (state.enemy_sprite_size * 0.5) * hscale
  
          transform_x = opts.x * 0.5
          x = transform_x * hscale
  
          y_magnitude = 0.45
          transform_y = opts.y * y_magnitude
          y = (-transform_y * vscale ** 5.5) + 50 * y_magnitude
  
          return opts.merge! x: x, y: y, w: w, h: h
        else
          raise "#{opts}"
          return nil
        end
      else
        return opts.merge! y: opts.y - 55
      end
    end
  end
  
  $game = Game.new
  
  def tick_game args
    $game.args = args
    $game.tick
  end
  
  $gtk.reset

#+end_src

*** 14 Vr - Let There Be Light - main.rb
#+begin_src ruby
  # ./samples/14_vr/04_let_there_be_light/app/main.rb
  require 'app/tick.rb'
  
  def tick args
    args.gtk.start_server! port: 9001, enable_in_prod: true
    tick_game args
  end

#+end_src

*** 14 Vr - Let There Be Light - tick.rb
#+begin_src ruby
  # ./samples/14_vr/04_let_there_be_light/app/tick.rb
  class Game
    attr_gtk
  
    def tick
      grid.origin_center!
      defaults
      state.angle_shift_x ||= 180
      state.angle_shift_y ||= 180
  
      if inputs.controller_one.right_analog_y_perc.round(2) != 0.00
        args.state.star_distance += (inputs.controller_one.right_analog_y_perc * 0.25) ** 2 * inputs.controller_one.right_analog_y_perc.sign
        state.star_distance = state.star_distance.clamp(state.min_star_distance, state.max_star_distance)
        state.star_sprites = calc_star_primitives
      end
  
      render
    end
  
    def calc_star_primitives
      args.state.stars.map do |s|
        w = (32 * state.star_distance).clamp(1, 32)
        h = (32 * state.star_distance).clamp(1, 32)
        x = (state.max.x * state.star_distance) * s.xr
        y = (state.max.y * state.star_distance) * s.yr
        z = state.center.z + (state.max.z * state.star_distance * 10 * s.zr)
  
        angle_x = Math.atan2(z - 600, y).to_degrees + 90
        angle_y = Math.atan2(z - 600, x).to_degrees + 90
  
        draw_x = x - w.half
        draw_y = y - 40 - h.half
        draw_z = z
  
        { x: draw_x,
          y: draw_y,
          z: draw_z,
          b: 255,
          w: w,
          h: h,
          angle_x: angle_x,
          angle_y: angle_y,
          path: 'sprites/star.png' }
      end
    end
  
    def render
      outputs.background_color = [0, 0, 0]
      if gtk.platform? :macos
        args.outputs.borders << hmap(x: -150,
                                     y: -220,
                                     w: 300, h: 130, r: 255, g: 255, b: 255)
      end
  
      if state.star_distance <= 1.0
        text_alpha = (1 - state.star_distance) * 255
        args.outputs.labels << { x: 0, y: 50, text: "Let there be light.", r: 255, g: 255, b: 255, size_enum: 1, alignment_enum: 1, a: text_alpha }
        args.outputs.labels << { x: 0, y: 25, text: "(right analog: up/down)", r: 255, g: 255, b: 255, size_enum: -2, alignment_enum: 1, a: text_alpha }
      end
  
      args.outputs.sprites << state.star_sprites
    end
  
    def random_point
      r = { xr: 2.randomize(:ratio) - 1,
            yr: 2.randomize(:ratio) - 1,
            zr: 2.randomize(:ratio) - 1 }
      if (r.xr ** 2 + r.yr ** 2 + r.zr ** 2) > 1.0
        return random_point
      else
        return r
      end
    end
  
    def defaults
      state.max_star_distance ||= 100
      state.min_star_distance ||= 0.001
      state.star_distance     ||= 0.001
      state.star_angle        ||= 0
  
      state.center.x       ||= 0
      state.center.y       ||= 0
      state.center.z       ||= 30
      state.max.x          ||= 640
      state.max.y          ||= 640
      state.max.z          ||= 50
  
      state.stars ||= 500.map do
        random_point
      end
  
      state.star_sprites ||= calc_star_primitives
    end
  end
  
  $game = Game.new
  
  def tick_game args
    $game.args = args
    $game.tick
  end
  
  $gtk.reset

#+end_src

*** 14 Vr - Draw A Cube - main.rb
#+begin_src ruby
  # ./samples/14_vr/05_draw_a_cube/app/main.rb
  require 'app/tick.rb'
  
  def tick args
    args.gtk.start_server! port: 9001, enable_in_prod: true
    tick_game args
  end

#+end_src

*** 14 Vr - Draw A Cube - tick.rb
#+begin_src ruby
  # ./samples/14_vr/05_draw_a_cube/app/tick.rb
  def cube args, x, y, z, size
    sprite = { w: size, h: size, path: 'sprites/square/blue.png' }
    back   = { x: x,                 y: y,                 z: z - size.half + 1,              **sprite }
    front  = { x: x,                 y: y,                 z: z + size.half - 1,              **sprite }
    top    = { x: x,                 y: y + size.half - 1, z: z,                 angle_x: 90, **sprite }
    bottom = { x: x,                 y: y - size.half + 1, z: z,                 angle_x: 90, **sprite }
    left   = { x: x - size.half + 1, y: y,                 z: z,                 angle_y: 90, **sprite }
    right  = { x: x + size.half - 1, y: y,                 z: z,                 angle_y: 90, **sprite }
  
    # assumes cube is always in front of player
    # looking at cube straight on
    #    0         0
    if y == 0 && x == 0
      args.outputs.sprites << [back, left, top, bottom, right, front]
    end
  
    # looking at right side of cube, head on
    #    -         0
    if x < 0 && y == 0
      args.outputs.sprites << [back, left, top, bottom, right, front]
    end
  
    # looking at left side of the cube, head on
    #    +         0
    if x > 0 && y == 0
      args.outputs.sprites << [back, right, top, bottom, left, front]
    end
  
    # looking at top of the cube, head on
    #    0         -
    if x == 0 && y < 0
      args.outputs.sprites << [back, left, bottom, right, front, top]
    end
  
    # looking at bottom of the cube, head on
    #    0         +
    if x == 0 && y > 0
      args.outputs.sprites << [back, left, top, right, front, bottom]
    end
  
    # looking at right, and top of cube
    #    -        -
    if x < 0 && y < 0
      args.outputs.sprites << [back, left, bottom, right, top, front]
    end
  
    # looking at right, and bottom of cube
    #    -        +
    if x < 0 && y > 0
      args.outputs.sprites << [back, left, bottom, top, right, front]
    end
  
    # looking at left, and top of cube
    #    +        -
    if x > 0 && y < 0
      args.outputs.sprites << [back, right, bottom, left, top, front]
    end
  
    # looking at left, and bottom of cube
    #    +        +
    if x > 0 && y > 0
      args.outputs.sprites << [back, right, top, left, bottom, front]
    end
  end
  
  def tick_game args
    args.grid.origin_center!
    args.outputs.background_color = [0, 0, 0]
  
    args.state.x ||= 0
    args.state.y ||= 0
  
    args.state.x += 10 * args.inputs.controller_one.right_analog_x_perc
    args.state.y += 10 * args.inputs.controller_one.right_analog_y_perc * -1
  
    cube args, args.state.x, args.state.y, 0, 100
  end
  
  $gtk.reset

#+end_src

*** 14 Vr - Citadels - tick.rb
#+begin_src ruby
  # ./samples/14_vr/06_citadels/app/tick.rb
  class Game
    attr_gtk
  
    def citadel x, y, z
      angle = state.tick_count.idiv(10) % 360
      adjacent = 40
      adjacent = adjacent.ceil
      angle = Math.atan2(40, 70).to_degrees
      y += 500
      x -= 40
      back_sprites = [
        { z: z - 40 + adjacent.half,
          x: x,
          y: y + 75,
          w: 80, h: 80, angle_x: angle, path: "sprites/triangle/equilateral/blue.png" },
        { z: z - 40,
          x: x,
          y: y - 400 + 80,
          w: 80, h: 400, path: "sprites/square/blue.png" },
      ]
  
      left_sprites = [
        { z: z,
          x: x - 40 + adjacent.half,
          y: y + 75,
          w: 80, h: 80, angle_x: -angle, angle_y: 90, path: "sprites/triangle/equilateral/blue.png" },
        { z: z,                      x: x - 40,
          y: y - 400 + 80,
          w: 80, h: 400, angle_y: 90, path: "sprites/square/blue.png" },
      ]
  
      right_sprites = [
        { z: z,
          x: x + 40 - adjacent.half,
          y: y + 75,
          w: 80, h: 80, angle_x: angle, angle_y: 90, path: "sprites/triangle/equilateral/blue.png" },
        { z: z,
          x: x + 40,
          y: y - 400 + 80,
          w: 80, h: 400, angle_y: 90, path: "sprites/square/blue.png" },
      ]
  
      front_sprites = [
        { z: z + 40 - adjacent.half,
          x: x,
          y: y + 75,
          w: 80, h: 80, angle_x: -angle, path: "sprites/triangle/equilateral/blue.png" },
        { z: z + 40,
          x: x,
          y: y - 400 + 80,
          w: 80, h: 400, path: "sprites/square/blue.png" },
      ]
  
      if x > 700
        [
          back_sprites,
          right_sprites,
          front_sprites,
          left_sprites,
        ]
      elsif x < 600
        [
          back_sprites,
          left_sprites,
          front_sprites,
          right_sprites,
        ]
      else
        [
          back_sprites,
          left_sprites,
          right_sprites,
          front_sprites,
        ]
      end
  
    end
  
    def tick
      state.z ||= 200
      state.z += inputs.controller_one.right_analog_y_perc
      state.columns ||= 100.map do
        {
          x: rand(12) * 400,
          y: 0,
          z: rand(12) * 400,
        }
      end.sort_by { |col| -col.z }
  
      outputs.sprites << state.columns.map do |col|
        citadel(col.x - 640, col.y - 400, state.z - col.z)
      end
    end
  end
  
  $game = Game.new
  
  def tick_game args
    $game.args = args
    $game.tick
  end
  
  $gtk.reset

#+end_src

*** 14 Vr - Flappy Vr - credits.txt
#+begin_src ruby
  # ./samples/14_vr/07_flappy_vr/CREDITS.txt
  code: Amir Rajan, https://twitter.com/amirrajan
  graphics and audio: Nick Culbertson, https://twitter.com/MobyPixel
  

#+end_src

*** 14 Vr - Flappy Vr - main.rb
#+begin_src ruby
  # ./samples/14_vr/07_flappy_vr/app/main.rb
  require 'app/tick.rb'
  
  def tick args
    args.gtk.start_server! port: 9001, enable_in_prod: true
    tick_game args
  end

#+end_src

*** 14 Vr - Flappy Vr - tick.rb
#+begin_src ruby
  # ./samples/14_vr/07_flappy_vr/app/tick.rb
  class FlappyDragon
    attr_accessor :grid, :inputs, :state, :outputs
  
    def tick
      defaults
      render
      calc
      process_inputs
    end
  
    def defaults
      state.flap_power              = 11
      state.gravity                 = 0.9
      state.ceiling                 = 600
      state.ceiling_flap_power      = 6
      state.wall_countdown_length   = 100
      state.wall_gap_size           = 100
      state.wall_countdown        ||= 0
      state.hi_score              ||= 0
      state.score                 ||= 0
      state.walls                 ||= []
      state.x_starting_point      ||= 640
      state.x                     ||= state.x_starting_point
      state.y                     ||= 500
      state.z                     ||= -120
      state.dy                    ||= 0
      state.scene                 ||= :menu
      state.scene_at              ||= 0
      state.difficulty            ||= :normal
      state.new_difficulty        ||= :normal
      state.countdown             ||= 4.seconds
      state.flash_at              ||= 0
    end
  
    def render
      outputs.sounds << "sounds/flappy-song.ogg" if state.tick_count == 1
      render_score
      render_menu
      render_game
    end
  
    def render_score
      outputs.primitives << { x: 10, y: 710, text: "HI SCORE: #{state.hi_score}", **large_white_typeset }
      outputs.primitives << { x: 10, y: 680, text: "SCORE: #{state.score}", **large_white_typeset }
      outputs.primitives << { x: 10, y: 650, text: "DIFFICULTY: #{state.difficulty.upcase}", **large_white_typeset }
    end
  
    def render_menu
      return unless state.scene == :menu
      render_overlay
  
      outputs.labels << { x: 640, y: 700, z: -640, text: "Flappy Dragon", size_enum: 50, alignment_enum: 1, **white }
      outputs.labels << { x: 640, y: 500, z: -640, text: "Instructions: Press Spacebar to flap. Don't die.", size_enum: 4, alignment_enum: 1, **white }
      outputs.labels << { x: 430, y: 430, z: -640, text: "[Tab]    Change difficulty", size_enum: 4, alignment_enum: 0, **white }
      outputs.labels << { x: 430, y: 400, z: -640, text: "[Enter]  Start at New Difficulty ", size_enum: 4, alignment_enum: 0, **white }
      outputs.labels << { x: 430, y: 370, z: -640, text: "[Escape] Cancel/Resume ", size_enum: 4, alignment_enum: 0, **white }
      outputs.labels << { x: 640, y: 300, z: -640, text: "(mouse, touch, and game controllers work, too!) ", size_enum: 4, alignment_enum: 1, **white }
      outputs.labels << { x: 640, y: 200, z: -640, text: "Difficulty: #{state.new_difficulty.capitalize}", size_enum: 4, alignment_enum: 1, **white }
  
      outputs.labels << { x: 10, y: 100, z: -640, text: "Code:   @amirrajan",     **white }
      outputs.labels << { x: 10, y:  80, z: -640, text: "Art:    @mobypixel",     **white }
      outputs.labels << { x: 10, y:  60, z: -640, text: "Music:  @mobypixel",     **white }
      outputs.labels << { x: 10, y:  40, z: -640, text: "Engine: DragonRuby GTK", **white }
    end
  
    def render_overlay
      overlay_rect = grid.rect.scale_rect(1.1, 0, 0)
      outputs.primitives << { x: overlay_rect.x - overlay_rect.w,
                              y: overlay_rect.y - overlay_rect.h,
                              w: overlay_rect.w * 4,
                              h: overlay_rect.h * 2,
                              r: 0, g: 0, b: 0, a: 230 }.solid!
    end
  
    def render_game
      outputs.background_color = [0, 0, 0]
      render_game_over
      render_background
      render_walls
      render_dragon
      render_flash
    end
  
    def render_game_over
      return unless state.scene == :game
      outputs.labels << { x: 638, y: 358, text: score_text,     z: -120, size_enum: 20, alignment_enum: 1 }
      outputs.labels << { x: 635, y: 360, text: score_text,     z: -120, size_enum: 20, alignment_enum: 1, r: 255, g: 255, b: 255 }
      outputs.labels << { x: 638, y: 428, text: countdown_text, z: -120, size_enum: 20, alignment_enum: 1 }
      outputs.labels << { x: 635, y: 430, text: countdown_text, z: -120, size_enum: 20, alignment_enum: 1, r: 255, g: 255, b: 255 }
    end
  
    def render_background
      scroll_point_at   = state.tick_count
      scroll_point_at   = state.scene_at if state.scene == :menu
      scroll_point_at   = state.death_at if state.countdown > 0
      scroll_point_at ||= 0
  
      outputs.sprites << { x: -640, y: -360, z: -640, w: 1280 * 2, h: 720 * 2, path: 'sprites/background.png' }
      outputs.sprites << scrolling_background(scroll_point_at, 'sprites/parallax_back.png',   0.25, 0)
      outputs.sprites << scrolling_background(scroll_point_at, 'sprites/parallax_middle.png', 0.50, 50)
      outputs.sprites << scrolling_background(scroll_point_at, 'sprites/parallax_front.png',  1.00, 100, -80)
    end
  
    def scrolling_background at, path, rate, z, y = 0
      rate *= 2
      w = 1440 * 2
      h =  720 * 2
      [
        { x: w - at.*(rate) % w - w.half.half, y: y * 2 - 360, z: -640 + z, w: w, h: h, path: path },
        { x: 0 - at.*(rate) % w - w.half.half, y: y * 2 - 360, z: -640 + z, w: w, h: h, path: path },
      ]
    end
  
    def render_walls
      state.walls.each do |w|
        w.top_section = { x: w.x,
                          y: w.bottom_height - 720,
                          z: -120,
                          w: 100,
                          h: 720,
                          path: 'sprites/wall.png',
                          angle: 180 }
  
        w.bottom_section = { x: w.x,
                             y: w.top_y,
                             z: -120,
                             w: 100,
                             h: 720,
                             path: 'sprites/wallbottom.png',
                             angle: 0}
        w.sprites = [
          model_for(w.top_section),
          model_for(w.bottom_section)
        ]
      end
  
      outputs.sprites << state.walls.find_all { |w| w.x >= state.x }.reverse.map(&:sprites)
      outputs.sprites << state.walls.find_all { |w| w.x <  state.x }.map(&:sprites)
    end
  
    def model_for wall
      ratio = (wall.x - state.x_starting_point).abs.fdiv(2560 + state.x_starting_point)
      z_ratio = ratio ** 2
      z_offset = (2560 * 2) * z_ratio
      x_offset = z_offset * 0.25
  
      if wall.x < state.x
        x_offset *= -1
      end
  
      a = 255 * (1 - z_ratio)
  
      back  = { x:     wall.x + x_offset,
                y:     wall.y,
                z:     wall.z - wall.w.half - z_offset,
                a:     a,
                w:     wall.w,
                h:     wall.h,
                path:  wall.path,
                angle: wall.angle }
      front = { x:     wall.x + x_offset,
                y:     wall.y,
                z:     wall.z + wall.w.half - z_offset,
                a:     a,
                w:     wall.w,
                h:     wall.h,
                path:  wall.path,
                angle: wall.angle }
      left  = { x:     wall.x - wall.w.half + x_offset,
                y:     wall.y,
                z:     wall.z - z_offset,
                a:     a,
                angle_y: 90,
                w:     wall.w,
                h:     wall.h,
                path:  wall.path,
                angle: wall.angle }
      right = { x:     wall.x + wall.w.half + x_offset,
                y:     wall.y,
                z:     wall.z - z_offset,
                a:     a,
                angle_y: 90,
                w:     wall.w,
                h:     wall.h,
                path:  wall.path,
                angle: wall.angle }
      if    (wall.x - wall.w - state.x).abs < 200
        [back, left, right, front]
      elsif wall.x < state.x
        [back, left, front, right]
      else
        [back, right, front, left]
      end
    end
  
    def render_dragon
      state.show_death = true if state.countdown == 3.seconds
  
      if state.show_death == false || !state.death_at
        animation_index = state.flapped_at.frame_index 6, 2, false if state.flapped_at
        sprite_name = "sprites/dragon_fly#{animation_index.or(0) + 1}.png"
        state.dragon_sprite = { x: state.x, y: state.y, z: state.z, w: 100, h: 80, path: sprite_name, angle: state.dy * 1.2 }
      else
        sprite_name = "sprites/dragon_die.png"
        state.dragon_sprite = { x: state.x, y: state.y, z: state.z, w: 100, h: 80, path: sprite_name, angle: state.dy * 1.2 }
        sprite_changed_elapsed    = state.death_at.elapsed_time - 1.seconds
        state.dragon_sprite.angle += (sprite_changed_elapsed ** 1.3) * state.death_fall_direction * -1
        state.dragon_sprite.x     += (sprite_changed_elapsed ** 1.2) * state.death_fall_direction
        state.dragon_sprite.y     += (sprite_changed_elapsed * 14 - sprite_changed_elapsed ** 1.6)
        state.z     += 0.3
      end
  
      outputs.sprites << state.dragon_sprite
    end
  
    def render_flash
      return unless state.flash_at
  
      outputs.primitives << { **grid.rect.to_hash,
                              **white,
                              a: 255 * state.flash_at.ease(20, :flip) }.solid!
  
      state.flash_at = 0 if state.flash_at.elapsed_time > 20
    end
  
    def calc
      return unless state.scene == :game
      reset_game if state.countdown == 1
      state.countdown -= 1 and return if state.countdown > 0
      calc_walls
      calc_flap
      calc_game_over
    end
  
    def calc_walls
      state.walls.each { |w| w.x -= 8 }
  
      walls_count_before_removal = state.walls.length
  
      state.walls.reject! { |w| w.x < -2560 + state.x_starting_point }
  
      state.score += 1 if state.walls.count < walls_count_before_removal
  
      state.wall_countdown -= 1 and return if state.wall_countdown > 0
  
      state.walls << state.new_entity(:wall) do |w|
        w.x             = 2560 + state.x_starting_point
        w.opening       = grid.top
                              .randomize(:ratio)
                              .greater(200)
                              .lesser(520)
        w.opening -= w.opening * 0.5
        w.bottom_height = w.opening - state.wall_gap_size
        w.top_y         = w.opening + state.wall_gap_size
      end
  
      state.wall_countdown = state.wall_countdown_length
    end
  
    def calc_flap
      state.y += state.dy
      state.dy = state.dy.lesser state.flap_power
      state.dy -= state.gravity
      return if state.y < state.ceiling
      state.y  = state.ceiling
      state.dy = state.dy.lesser state.ceiling_flap_power
    end
  
    def calc_game_over
      return unless game_over?
  
      state.death_at = state.tick_count
      state.death_from = state.walls.first
      state.death_fall_direction = -1
      state.death_fall_direction =  1 if state.x > state.death_from.x
      outputs.sounds << "sounds/hit-sound.wav"
      begin_countdown
    end
  
    def process_inputs
      process_inputs_menu
      process_inputs_game
    end
  
    def process_inputs_menu
      return unless state.scene == :menu
  
      changediff = inputs.keyboard.key_down.tab || inputs.controller_one.key_down.select
      if inputs.mouse.click
        p = inputs.mouse.click.point
        if (p.y >= 165) && (p.y < 200) && (p.x >= 500) && (p.x < 800)
          changediff = true
        end
      end
  
      if changediff
        case state.new_difficulty
        when :easy
          state.new_difficulty = :normal
        when :normal
          state.new_difficulty = :hard
        when :hard
          state.new_difficulty = :flappy
        when :flappy
          state.new_difficulty = :easy
        end
      end
  
      if inputs.keyboard.key_down.enter || inputs.controller_one.key_down.start || inputs.controller_one.key_down.a
        state.difficulty = state.new_difficulty
        change_to_scene :game
        reset_game false
        state.hi_score = 0
        begin_countdown
      end
  
      if inputs.keyboard.key_down.escape || (inputs.mouse.click && !changediff) || inputs.controller_one.key_down.b
        state.new_difficulty = state.difficulty
        change_to_scene :game
      end
    end
  
    def process_inputs_game
      return unless state.scene == :game
  
      clicked_menu = false
      if inputs.mouse.click
        p = inputs.mouse.click.point
        clicked_menu = (p.y >= 620) && (p.x < 275)
      end
  
      if clicked_menu || inputs.keyboard.key_down.escape || inputs.keyboard.key_down.enter || inputs.controller_one.key_down.start
        change_to_scene :menu
      elsif (inputs.mouse.down || inputs.mouse.click || inputs.keyboard.key_down.space || inputs.controller_one.key_down.a) && state.countdown == 0
        state.dy = 0
        state.dy += state.flap_power
        state.flapped_at = state.tick_count
        outputs.sounds << "sounds/fly-sound.wav"
      end
    end
  
    def white
      { r: 255, g: 255, b: 255 }
    end
  
    def large_white_typeset
      { size_enum: 5, alignment_enum: 0, r: 255, g: 255, b: 255 }
    end
  
    def at_beginning?
      state.walls.count == 0
    end
  
    def dragon_collision_box
      { x: state.dragon_sprite.x,
        y: state.dragon_sprite.y,
        w: state.dragon_sprite.w,
        h: state.dragon_sprite.h }
           .scale_rect(1.0 - collision_forgiveness, 0.5, 0.5)
           .rect_shift_right(10)
           .rect_shift_up(state.dy * 2)
    end
  
    def game_over?
      return true if state.y <= 0.-(500 * collision_forgiveness) && !at_beginning?
  
      state.walls
           .find_all { |w| w.top_section && w.bottom_section }
           .flat_map { |w| [w.top_section, w.bottom_section] }
           .any?     { |s| s.intersect_rect?(dragon_collision_box) }
    end
  
    def collision_forgiveness
      case state.difficulty
      when :easy
        0.9
      when :normal
        0.7
      when :hard
        0.5
      when :flappy
        0.3
      else
        0.9
      end
    end
  
    def countdown_text
      state.countdown ||= -1
      return ""          if state.countdown == 0
      return "GO!"       if state.countdown.idiv(60) == 0
      return "GAME OVER" if state.death_at
      return "READY?"
    end
  
    def begin_countdown
      state.countdown = 4.seconds
    end
  
    def score_text
      return ""                        unless state.countdown > 1.seconds
      return ""                        unless state.death_at
      return "SCORE: 0 (LOL)"          if state.score == 0
      return "HI SCORE: #{state.score}" if state.score == state.hi_score
      return "SCORE: #{state.score}"
    end
  
    def reset_game set_flash = true
      state.flash_at = state.tick_count if set_flash
      state.walls = []
      state.y = 500
      state.x =  state.x_starting_point
      state.z = -120
      state.dy = 0
      state.hi_score = state.hi_score.greater(state.score)
      state.score = 0
      state.wall_countdown = state.wall_countdown_length.fdiv(2)
      state.show_death = false
      state.death_at = nil
    end
  
    def change_to_scene scene
      state.scene = scene
      state.scene_at = state.tick_count
      inputs.keyboard.clear
      inputs.controller_one.clear
    end
  end
  
  $flappy_dragon = FlappyDragon.new
  
  def tick_game args
    $flappy_dragon.grid = args.grid
    $flappy_dragon.inputs = args.inputs
    $flappy_dragon.state = args.state
    $flappy_dragon.outputs = args.outputs
    $flappy_dragon.tick
  end
  
  $gtk.reset

#+end_src

*** 3d - 3d Cube - main.rb
#+begin_src ruby
  # ./samples/99_genre_3d/01_3d_cube/app/main.rb
  STARTX             = 0.0
  STARTY             = 0.0
  ENDY               = 20.0
  ENDX               = 20.0
  SPINPOINT          = 10
  SPINDURATION       = 400
  POINTSIZE          = 8
  BOXDEPTH           = 40
  YAW                = 1
  DISTANCE           = 10
  
  def tick args
    args.outputs.background_color = [0, 0, 0]
    a = Math.sin(args.state.tick_count / SPINDURATION) * Math.tan(args.state.tick_count / SPINDURATION)
    s = Math.sin(a)
    c = Math.cos(a)
    x = STARTX
    y = STARTY
    offset_x = (1280 - (ENDX - STARTX)) / 2
    offset_y =  (360 - (ENDY - STARTY)) / 2
  
    srand(1)
    while y < ENDY do
      while x < ENDX do
        if (y == STARTY ||
            y == (ENDY / 0.5) * 2 ||
            y == (ENDY / 0.5) * 2 + 0.5 ||
            y == ENDY - 0.5 ||
            x == STARTX ||
            x == ENDX - 0.5)
          z = rand(BOXDEPTH)
          z *= Math.sin(a / 2)
          x -= SPINPOINT
          u = (x * c) - (z * s)
          v = (x * s) + (z * c)
          k = DISTANCE.fdiv(100) + (v / 500 * YAW)
          u = u / k
          v = y / k
          w = POINTSIZE / 10 / k
          args.outputs.sprites << { x: offset_x + u - w, y: offset_y + v - w, w: w, h: w, path: 'sprites/square-blue.png'}
          x += SPINPOINT
        end
        x += 0.5
      end
      y += 0.5
      x = STARTX
    end
  end
  
  $gtk.reset

#+end_src

*** 3d - Wireframe - main.rb
#+begin_src ruby
  # ./samples/99_genre_3d/02_wireframe/app/main.rb
  def tick args
    args.state.model   ||= Object3D.new('data/shuttle.off')
    args.state.mtx     ||= rotate3D(0, 0, 0)
    args.state.inv_mtx ||= rotate3D(0, 0, 0)
    delta_mtx          = rotate3D(args.inputs.up_down * 0.01, input_roll(args) * 0.01, args.inputs.left_right * 0.01)
    args.outputs.lines << args.state.model.edges
    args.state.model.fast_3x3_transform! args.state.inv_mtx
    args.state.inv_mtx = mtx_mul(delta_mtx.transpose, args.state.inv_mtx)
    args.state.mtx     = mtx_mul(args.state.mtx, delta_mtx)
    args.state.model.fast_3x3_transform! args.state.mtx
    args.outputs.background_color = [0, 0, 0]
    args.outputs.debug << args.gtk.framerate_diagnostics_primitives
  end
  
  def input_roll args
    roll = 0
    roll += 1 if args.inputs.keyboard.e
    roll -= 1 if args.inputs.keyboard.q
    roll
  end
  
  def rotate3D(theta_x = 0.1, theta_y = 0.1, theta_z = 0.1)
    c_x, s_x = Math.cos(theta_x), Math.sin(theta_x)
    c_y, s_y = Math.cos(theta_y), Math.sin(theta_y)
    c_z, s_z = Math.cos(theta_z), Math.sin(theta_z)
    rot_x    = [[1, 0, 0], [0, c_x, -s_x], [0, s_x, c_x]]
    rot_y    = [[c_y, 0, s_y], [0, 1, 0], [-s_y, 0, c_y]]
    rot_z    = [[c_z, -s_z, 0], [s_z, c_z, 0], [0, 0, 1]]
    mtx_mul(mtx_mul(rot_x, rot_y), rot_z)
  end
  
  def mtx_mul(a, b)
    is = (0...a.length)
    js = (0...b[0].length)
    ks = (0...b.length)
    is.map do |i|
      js.map do |j|
        ks.map do |k|
          a[i][k] * b[k][j]
        end.reduce(&:plus)
      end
    end
  end
  
  class Object3D
    attr_reader :vert_count, :face_count, :edge_count, :verts, :faces, :edges
  
    def initialize(path)
      @vert_count = 0
      @face_count = 0
      @edge_count = 0
      @verts      = []
      @faces      = []
      @edges      = []
      _init_from_file path
    end
  
    def _init_from_file path
      file_lines = $gtk.read_file(path).split("\n")
                       .reject { |line| line.start_with?('#') || line.split(' ').length == 0 } # Strip out simple comments and blank lines
                       .map { |line| line.split('#')[0] } # Strip out end of line comments
                       .map { |line| line.split(' ') } # Tokenize by splitting on whitespace
      raise "OFF file did not start with OFF." if file_lines.shift != ["OFF"] # OFF meshes are supposed to begin with "OFF" as the first line.
      raise "<NVertices NFaces NEdges> line malformed" if file_lines[0].length != 3 # The second line needs to have 3 numbers. Raise an error if it doesn't.
      @vert_count, @face_count, @edge_count = file_lines.shift&.map(&:to_i) # Update the counts
      # Only the vertex and face counts need to be accurate. Raise an error if they are inaccurate.
      raise "Incorrect number of vertices and/or faces (Parsed VFE header: #{@vert_count} #{@face_count} #{@edge_count})" if file_lines.length != @vert_count + @face_count
      # Grab all the lines describing vertices.
      vert_lines = file_lines[0, @vert_count]
      # Grab all the lines describing faces.
      face_lines = file_lines[@vert_count, @face_count]
      # Create all the vertices
      @verts = vert_lines.map_with_index { |line, id| Vertex.new(line, id) }
      # Create all the faces
      @faces = face_lines.map { |line| Face.new(line, @verts) }
      # Create all the edges
      @edges = @faces.flat_map(&:edges).uniq do |edge|
        sorted = edge.sorted
        [sorted.point_a, sorted.point_b]
      end
    end
  
    def fast_3x3_transform! mtx
      @verts.each { |vert| vert.fast_3x3_transform! mtx }
    end
  end
  
  class Face
  
    attr_reader :verts, :edges
  
    def initialize(data, verts)
      vert_count = data[0].to_i
      vert_ids   = data[1, vert_count].map(&:to_i)
      @verts     = vert_ids.map { |i| verts[i] }
      @edges     = []
      (0...vert_count).each { |i| @edges[i] = Edge.new(verts[vert_ids[i - 1]], verts[vert_ids[i]]) }
      @edges.rotate! 1
    end
  end
  
  class Edge
    attr_reader :point_a, :point_b
  
    def initialize(point_a, point_b)
      @point_a = point_a
      @point_b = point_b
    end
  
    def sorted
      @point_a.id < @point_b.id ? self : Edge.new(@point_b, @point_a)
    end
  
    def draw_override ffi
      ffi.draw_line(@point_a.render_x, @point_a.render_y, @point_b.render_x, @point_b.render_y, 255, 0, 0, 128)
      ffi.draw_line(@point_a.render_x+1, @point_a.render_y, @point_b.render_x+1, @point_b.render_y, 255, 0, 0, 128)
      ffi.draw_line(@point_a.render_x, @point_a.render_y+1, @point_b.render_x, @point_b.render_y+1, 255, 0, 0, 128)
      ffi.draw_line(@point_a.render_x+1, @point_a.render_y+1, @point_b.render_x+1, @point_b.render_y+1, 255, 0, 0, 128)
    end
  
    def primitive_marker
      :line
    end
  end
  
  class Vertex
    attr_accessor :x, :y, :z, :id
  
    def initialize(data, id)
      @x  = data[0].to_f
      @y  = data[1].to_f
      @z  = data[2].to_f
      @id = id
    end
  
    def fast_3x3_transform! mtx
      _x, _y, _z = @x, @y, @z
      @x         = mtx[0][0] * _x + mtx[0][1] * _y + mtx[0][2] * _z
      @y         = mtx[1][0] * _x + mtx[1][1] * _y + mtx[1][2] * _z
      @z         = mtx[2][0] * _x + mtx[2][1] * _y + mtx[2][2] * _z
    end
  
    def render_x
      @x * (10 / (5 - @y)) * 170 + 640
    end
  
    def render_y
      @z * (10 / (5 - @y)) * 170 + 360
    end
  end
#+end_src

*** 3d - Wireframe - Data - what-is-this.txt
#+begin_src ruby
  # ./samples/99_genre_3d/02_wireframe/data/what-is-this.txt
  https://en.wikipedia.org/wiki/OFF_(file_format)
#+end_src

*** 3d - Yaw Pitch Roll - main.rb
#+begin_src ruby
  # ./samples/99_genre_3d/03_yaw_pitch_roll/app/main.rb
  class Game
    attr_gtk
  
    def tick
      defaults
      render
      input
    end
  
    def matrix_mul m, v
      (hmap x: ((m.x.x * v.x) + (m.x.y * v.y) + (m.x.z * v.z) + (m.x.w * v.w)),
            y: ((m.y.x * v.x) + (m.y.y * v.y) + (m.y.z * v.z) + (m.y.w * v.w)),
            z: ((m.z.x * v.x) + (m.z.y * v.y) + (m.z.z * v.z) + (m.z.w * v.w)),
            w: ((m.w.x * v.x) + (m.w.y * v.y) + (m.w.z * v.z) + (m.w.w * v.w)))
    end
  
    def player_ship
      [
        # engine back
        { x: -1, y: -1, z: 1, w: 0 },
        { x: -1, y:  1, z: 1, w: 0 },
  
        { x: -1, y:  1, z: 1, w: 0 },
        { x:  1, y:  1, z: 1, w: 0 },
  
        { x:  1, y:  1, z: 1, w: 0 },
        { x:  1, y: -1, z: 1, w: 0 },
  
        { x:  1, y: -1, z: 1, w: 0 },
        { x: -1, y: -1, z: 1, w: 0 },
  
        # engine front
        { x: -1, y: -1, z: -1, w: 0 },
        { x: -1, y:  1, z: -1, w: 0 },
  
        { x: -1, y:  1, z: -1, w: 0 },
        { x:  1, y:  1, z: -1, w: 0 },
  
        { x:  1, y:  1, z: -1, w: 0 },
        { x:  1, y: -1, z: -1, w: 0 },
  
        { x:  1, y: -1, z: -1, w: 0 },
        { x: -1, y: -1, z: -1, w: 0 },
  
        # engine left
        { x: -1, z:  -1, y: -1, w: 0 },
        { x: -1, z:  -1, y:  1, w: 0 },
  
        { x: -1, z:  -1, y:  1, w: 0 },
        { x: -1, z:   1, y:  1, w: 0 },
  
        { x: -1, z:   1, y:  1, w: 0 },
        { x: -1, z:   1, y: -1, w: 0 },
  
        { x: -1, z:   1, y: -1, w: 0 },
        { x: -1, z:  -1, y: -1, w: 0 },
  
        # engine right
        { x:  1, z:  -1, y: -1, w: 0 },
        { x:  1, z:  -1, y:  1, w: 0 },
  
        { x:  1, z:  -1, y:  1, w: 0 },
        { x:  1, z:   1, y:  1, w: 0 },
  
        { x:  1, z:   1, y:  1, w: 0 },
        { x:  1, z:   1, y: -1, w: 0 },
  
        { x:  1, z:   1, y: -1, w: 0 },
        { x:  1, z:  -1, y: -1, w: 0 },
  
        # top front of engine to front of ship
        { x:  1, y:   1, z: 1, w: 0 },
        { x:  0, y:  -1, z: 9, w: 0 },
  
        { x:  0, y:  -1, z: 9, w: 0 },
        { x: -1, y:   1, z: 1, w: 0 },
  
        # bottom front of engine
        { x:  1, y:  -1, z: 1, w: 0 },
        { x:  0, y:  -1, z: 9, w: 0 },
  
        { x: -1, y:  -1, z: 1, w: 0 },
        { x:  0, y:  -1, z: 9, w: 0 },
  
        # right wing
        # front of wing
        { x: 1, y: 0.10, z:  1, w: 0 },
        { x: 9, y: 0.10, z: -1, w: 0 },
  
        { x:  9, y: 0.10, z: -1, w: 0 },
        { x: 10, y: 0.10, z: -2, w: 0 },
  
        # back of wing
        { x: 1, y: 0.10, z: -1, w: 0 },
        { x: 9, y: 0.10, z: -1, w: 0 },
  
        { x: 10, y: 0.10, z: -2, w: 0 },
        { x:  8, y: 0.10, z: -1, w: 0 },
  
        # front of wing
        { x: 1, y: -0.10, z:  1, w: 0 },
        { x: 9, y: -0.10, z: -1, w: 0 },
  
        { x:  9, y: -0.10, z: -1, w: 0 },
        { x: 10, y: -0.10, z: -2, w: 0 },
  
        # back of wing
        { x: 1, y: -0.10, z: -1, w: 0 },
        { x: 9, y: -0.10, z: -1, w: 0 },
  
        { x: 10, y: -0.10, z: -2, w: 0 },
        { x:  8, y: -0.10, z: -1, w: 0 },
  
        # left wing
        # front of wing
        { x: -1, y: 0.10, z:  1, w: 0 },
        { x: -9, y: 0.10, z: -1, w: 0 },
  
        { x: -9, y: 0.10, z: -1, w: 0 },
        { x: -10, y: 0.10, z: -2, w: 0 },
  
        # back of wing
        { x: -1, y: 0.10, z: -1, w: 0 },
        { x: -9, y: 0.10, z: -1, w: 0 },
  
        { x: -10, y: 0.10, z: -2, w: 0 },
        { x: -8, y: 0.10, z: -1, w: 0 },
  
        # front of wing
        { x: -1, y: -0.10, z:  1, w: 0 },
        { x: -9, y: -0.10, z: -1, w: 0 },
  
        { x: -9, y: -0.10, z: -1, w: 0 },
        { x: -10, y: -0.10, z: -2, w: 0 },
  
        # back of wing
        { x: -1, y: -0.10, z: -1, w: 0 },
        { x: -9, y: -0.10, z: -1, w: 0 },
  
        { x: -10, y: -0.10, z: -2, w: 0 },
        { x: -8, y: -0.10, z: -1, w: 0 },
  
        # left fin
        # top
        { x: -1, y: 0.10, z: 1, w: 0 },
        { x: -1, y: 3, z: -3, w: 0 },
  
        { x: -1, y: 0.10, z: -1, w: 0 },
        { x: -1, y: 3, z: -3, w: 0 },
  
        { x: -1.1, y: 0.10, z: 1, w: 0 },
        { x: -1.1, y: 3, z: -3, w: 0 },
  
        { x: -1.1, y: 0.10, z: -1, w: 0 },
        { x: -1.1, y: 3, z: -3, w: 0 },
  
        # bottom
        { x: -1, y: -0.10, z: 1, w: 0 },
        { x: -1, y: -2, z: -2, w: 0 },
  
        { x: -1, y: -0.10, z: -1, w: 0 },
        { x: -1, y: -2, z: -2, w: 0 },
  
        { x: -1.1, y: -0.10, z: 1, w: 0 },
        { x: -1.1, y: -2, z: -2, w: 0 },
  
        { x: -1.1, y: -0.10, z: -1, w: 0 },
        { x: -1.1, y: -2, z: -2, w: 0 },
  
        # right fin
        { x:  1, y: 0.10, z: 1, w: 0 },
        { x:  1, y: 3, z: -3, w: 0 },
  
        { x:  1, y: 0.10, z: -1, w: 0 },
        { x:  1, y: 3, z: -3, w: 0 },
  
        { x:  1.1, y: 0.10, z: 1, w: 0 },
        { x:  1.1, y: 3, z: -3, w: 0 },
  
        { x:  1.1, y: 0.10, z: -1, w: 0 },
        { x:  1.1, y: 3, z: -3, w: 0 },
  
        # bottom
        { x:  1, y: -0.10, z: 1, w: 0 },
        { x:  1, y: -2, z: -2, w: 0 },
  
        { x:  1, y: -0.10, z: -1, w: 0 },
        { x:  1, y: -2, z: -2, w: 0 },
  
        { x:  1.1, y: -0.10, z: 1, w: 0 },
        { x:  1.1, y: -2, z: -2, w: 0 },
  
        { x:  1.1, y: -0.10, z: -1, w: 0 },
        { x:  1.1, y: -2, z: -2, w: 0 },
      ]
    end
  
    def defaults
      state.points ||= player_ship
      state.shifted_points ||= state.points.map { |point| point }
  
      state.scale   ||= 1
      state.angle_x ||= 0
      state.angle_y ||= 0
      state.angle_z ||= 0
    end
  
    def matrix_new x0, y0, z0, w0, x1, y1, z1, w1, x2, y2, z2, w2, x3, y3, z3, w3
      (hmap x: (hmap x: x0, y: y0, z: z0, w: w0),
            y: (hmap x: x1, y: y1, z: z1, w: w1),
            z: (hmap x: x2, y: y2, z: z2, w: w2),
            w: (hmap x: x3, y: y3, z: z3, w: w3))
    end
  
    def angle_z_matrix degrees
      cos_t = Math.cos degrees.to_radians
      sin_t = Math.sin degrees.to_radians
      (matrix_new cos_t, -sin_t, 0, 0,
                  sin_t,  cos_t, 0, 0,
                  0,      0,     1, 0,
                  0,      0,     0, 1)
    end
  
    def angle_y_matrix degrees
      cos_t = Math.cos degrees.to_radians
      sin_t = Math.sin degrees.to_radians
      (matrix_new  cos_t,  0, sin_t, 0,
                   0,      1, 0,     0,
                   -sin_t, 0, cos_t, 0,
                   0,      0, 0,     1)
    end
  
    def angle_x_matrix degrees
      cos_t = Math.cos degrees.to_radians
      sin_t = Math.sin degrees.to_radians
      (matrix_new  1,     0,      0, 0,
                   0, cos_t, -sin_t, 0,
                   0, sin_t,  cos_t, 0,
                   0,     0,      0, 1)
    end
  
    def scale_matrix factor
      (matrix_new factor,      0,      0, 0,
                  0,      factor,      0, 0,
                  0,           0, factor, 0,
                  0,           0,      0, 1)
    end
  
    def input
      if (inputs.keyboard.shift && inputs.keyboard.p)
        state.scale -= 0.1
      elsif  inputs.keyboard.p
        state.scale += 0.1
      end
  
      if inputs.mouse.wheel
        state.scale += inputs.mouse.wheel.y
      end
  
      state.scale = state.scale.clamp(0.1, 1000)
  
      if (inputs.keyboard.shift && inputs.keyboard.y) || inputs.keyboard.right
        state.angle_y += 1
      elsif (inputs.keyboard.y) || inputs.keyboard.left
        state.angle_y -= 1
      end
  
      if (inputs.keyboard.shift && inputs.keyboard.x) || inputs.keyboard.down
        state.angle_x -= 1
      elsif (inputs.keyboard.x || inputs.keyboard.up)
        state.angle_x += 1
      end
  
      if inputs.keyboard.shift && inputs.keyboard.z
        state.angle_z += 1
      elsif inputs.keyboard.z
        state.angle_z -= 1
      end
  
      if inputs.keyboard.zero
        state.angle_x = 0
        state.angle_y = 0
        state.angle_z = 0
      end
  
      angle_x = state.angle_x
      angle_y = state.angle_y
      angle_z = state.angle_z
      scale   = state.scale
  
      s_matrix = scale_matrix state.scale
      x_matrix = angle_z_matrix angle_z
      y_matrix = angle_y_matrix angle_y
      z_matrix = angle_x_matrix angle_x
  
      state.shifted_points = state.points.map do |point|
        (matrix_mul s_matrix,
                    (matrix_mul z_matrix,
                                (matrix_mul x_matrix,
                                            (matrix_mul y_matrix, point)))).merge(original: point)
      end
    end
  
    def thick_line line
      [
        line.merge(y: line.y - 1, y2: line.y2 - 1, r: 0, g: 0, b: 0),
        line.merge(x: line.x - 1, x2: line.x2 - 1, r: 0, g: 0, b: 0),
        line.merge(x: line.x - 0, x2: line.x2 - 0, r: 0, g: 0, b: 0),
        line.merge(y: line.y + 1, y2: line.y2 + 1, r: 0, g: 0, b: 0),
        line.merge(x: line.x + 1, x2: line.x2 + 1, r: 0, g: 0, b: 0)
      ]
    end
  
    def render
      outputs.lines << state.shifted_points.each_slice(2).map do |(p1, p2)|
        perc = 0
        thick_line({ x:  p1.x.*(10) + 640, y:  p1.y.*(10) + 320,
                     x2: p2.x.*(10) + 640, y2: p2.y.*(10) + 320,
                     r: 255 * perc,
                     g: 255 * perc,
                     b: 255 * perc })
      end
  
      outputs.labels << [ 10, 700, "angle_x: #{state.angle_x.to_sf}", 0]
      outputs.labels << [ 10, 670, "x, shift+x", 0]
  
      outputs.labels << [210, 700, "angle_y: #{state.angle_y.to_sf}", 0]
      outputs.labels << [210, 670, "y, shift+y", 0]
  
      outputs.labels << [410, 700, "angle_z: #{state.angle_z.to_sf}", 0]
      outputs.labels << [410, 670, "z, shift+z", 0]
  
      outputs.labels << [610, 700, "scale: #{state.scale.to_sf}", 0]
      outputs.labels << [610, 670, "p, shift+p", 0]
    end
  end
  
  $game = Game.new
  
  def tick args
    $game.args = args
    $game.tick
  end
  
  def set_angles x, y, z
    $game.state.angle_x = x
    $game.state.angle_y = y
    $game.state.angle_z = z
  end
  
  $gtk.reset

#+end_src

*** Arcade - Bullet Hell - main.rb
#+begin_src ruby
  # ./samples/99_genre_arcade/bullet_hell/app/main.rb
  def tick args
    args.state.base_columns   ||= 10.times.map { |n| 50 * n + 1280 / 2 - 5 * 50 + 5 }
    args.state.base_rows      ||= 5.times.map { |n| 50 * n + 720 - 5 * 50 }
    args.state.offset_columns = 10.times.map { |n| (n - 4.5) * Math.sin(Kernel.tick_count.to_radians) * 12 }
    args.state.offset_rows    = 5.map { 0 }
    args.state.columns        = 10.times.map { |i| args.state.base_columns[i] + args.state.offset_columns[i] }
    args.state.rows           = 5.times.map { |i| args.state.base_rows[i] + args.state.offset_rows[i] }
    args.state.explosions     ||= []
    args.state.enemies        ||= []
    args.state.score          ||= 0
    args.state.wave           ||= 0
    if args.state.enemies.empty?
      args.state.wave      += 1
      args.state.wave_root = Math.sqrt(args.state.wave)
      args.state.enemies   = make_enemies
    end
    args.state.player         ||= {x: 620, y: 80, w: 40, h: 40, path: 'sprites/circle-gray.png', angle: 90, cooldown: 0, alive: true}
    args.state.enemy_bullets  ||= []
    args.state.player_bullets ||= []
    args.state.lives          ||= 3
    args.state.missed_shots   ||= 0
    args.state.fired_shots    ||= 0
  
    update_explosions args
    update_enemy_positions args
  
    if args.inputs.left && args.state.player[:x] > (300 + 5)
      args.state.player[:x] -= 5
    end
    if args.inputs.right && args.state.player[:x] < (1280 - args.state.player[:w] - 300 - 5)
      args.state.player[:x] += 5
    end
  
    args.state.enemy_bullets.each do |bullet|
      bullet[:x] += bullet[:dx]
      bullet[:y] += bullet[:dy]
    end
    args.state.player_bullets.each do |bullet|
      bullet[:x] += bullet[:dx]
      bullet[:y] += bullet[:dy]
    end
  
    args.state.enemy_bullets  = args.state.enemy_bullets.find_all { |bullet| bullet[:y].between?(-16, 736) }
    args.state.player_bullets = args.state.player_bullets.find_all do |bullet|
      if bullet[:y].between?(-16, 736)
        true
      else
        args.state.missed_shots += 1
        false
      end
    end
  
    args.state.enemies = args.state.enemies.reject do |enemy|
      if args.state.player[:alive] && 1500 > (args.state.player[:x] - enemy[:x]) ** 2 + (args.state.player[:y] - enemy[:y]) ** 2
        args.state.explosions << {x: enemy[:x] + 4, y: enemy[:y] + 4, w: 32, h: 32, path: 'sprites/explosion-0.png', age: 0}
        args.state.explosions << {x: args.state.player[:x] + 4, y: args.state.player[:y] + 4, w: 32, h: 32, path: 'sprites/explosion-0.png', age: 0}
        args.state.player[:alive] = false
        true
      else
        false
      end
    end
    args.state.enemy_bullets.each do |bullet|
      if args.state.player[:alive] && 400 > (args.state.player[:x] - bullet[:x] + 12) ** 2 + (args.state.player[:y] - bullet[:y] + 12) ** 2
        args.state.explosions << {x: args.state.player[:x] + 4, y: args.state.player[:y] + 4, w: 32, h: 32, path: 'sprites/explosion-0.png', age: 0}
        args.state.player[:alive] = false
        bullet[:despawn]          = true
      end
    end
    args.state.enemies = args.state.enemies.reject do |enemy|
      args.state.player_bullets.any? do |bullet|
        if 400 > (enemy[:x] - bullet[:x] + 12) ** 2 + (enemy[:y] - bullet[:y] + 12) ** 2
          args.state.explosions << {x: enemy[:x] + 4, y: enemy[:y] + 4, w: 32, h: 32, path: 'sprites/explosion-0.png', age: 0}
          bullet[:despawn] = true
          args.state.score += 1000 * args.state.wave
          true
        else
          false
        end
      end
    end
  
    args.state.player_bullets = args.state.player_bullets.reject { |bullet| bullet[:despawn] }
    args.state.enemy_bullets  = args.state.enemy_bullets.reject { |bullet| bullet[:despawn] }
  
    args.state.player[:cooldown] -= 1
    if args.inputs.keyboard.key_held.space && args.state.player[:cooldown] <= 0 && args.state.player[:alive]
      args.state.player_bullets << {x: args.state.player[:x] + 12, y: args.state.player[:y] + 28, w: 16, h: 16, path: 'sprites/star.png', dx: 0, dy: 8}.sprite
      args.state.fired_shots       += 1
      args.state.player[:cooldown] = 10 + 20 / args.state.wave
    end
    args.state.enemies.each do |enemy|
      if Math.rand < 0.0005 + 0.0005 * args.state.wave && args.state.player[:alive] && enemy[:move_state] == :normal
        args.state.enemy_bullets << {x: enemy[:x] + 12, y: enemy[:y] - 8, w: 16, h: 16, path: 'sprites/star.png', dx: 0, dy: -3 - args.state.wave_root}.sprite
      end
    end
  
    args.outputs.background_color = [0, 0, 0]
    args.outputs.primitives << args.state.enemies.map do |enemy|
      [enemy[:x], enemy[:y], 40, 40, enemy[:path], -90].sprite
    end
    args.outputs.primitives << args.state.player if args.state.player[:alive]
    args.outputs.primitives << args.state.explosions
    args.outputs.primitives << args.state.player_bullets
    args.outputs.primitives << args.state.enemy_bullets
    accuracy = args.state.fired_shots.zero? ? 1 : (args.state.fired_shots - args.state.missed_shots) / args.state.fired_shots
    args.outputs.primitives << [
      [0, 0, 300, 720, 96, 0, 0].solid,
      [1280 - 300, 0, 300, 720, 96, 0, 0].solid,
      [1280 - 290, 60, "Wave     #{args.state.wave}", 255, 255, 255].label,
      [1280 - 290, 40, "Accuracy #{(accuracy * 100).floor}%", 255, 255, 255].label,
      [1280 - 290, 20, "Score    #{(args.state.score * accuracy).floor}", 255, 255, 255].label,
    ]
    args.outputs.primitives << args.state.lives.times.map do |n|
      [1280 - 290 + 50 * n, 80, 40, 40, 'sprites/circle-gray.png', 90].sprite
    end
    #args.outputs.debug << args.gtk.framerate_diagnostics_primitives
  
    if (!args.state.player[:alive]) && args.state.enemy_bullets.empty? && args.state.explosions.empty? && args.state.enemies.all? { |enemy| enemy[:move_state] == :normal }
      args.state.player[:alive] = true
      args.state.player[:x]     = 624
      args.state.player[:y]     = 80
      args.state.lives          -= 1
      if args.state.lives == -1
        args.state.clear!
      end
    end
  end
  
  def make_enemies
    enemies = []
    enemies += 10.times.map { |n| {x: Math.rand * 1280 * 2 - 640, y: Math.rand * 720 * 2 + 720, row: 0, col: n, path: 'sprites/circle-orange.png', move_state: :retreat} }
    enemies += 10.times.map { |n| {x: Math.rand * 1280 * 2 - 640, y: Math.rand * 720 * 2 + 720, row: 1, col: n, path: 'sprites/circle-orange.png', move_state: :retreat} }
    enemies += 8.times.map { |n| {x: Math.rand * 1280 * 2 - 640, y: Math.rand * 720 * 2 + 720, row: 2, col: n + 1, path: 'sprites/circle-blue.png', move_state: :retreat} }
    enemies += 8.times.map { |n| {x: Math.rand * 1280 * 2 - 640, y: Math.rand * 720 * 2 + 720, row: 3, col: n + 1, path: 'sprites/circle-blue.png', move_state: :retreat} }
    enemies += 4.times.map { |n| {x: Math.rand * 1280 * 2 - 640, y: Math.rand * 720 * 2 + 720, row: 4, col: n + 3, path: 'sprites/circle-green.png', move_state: :retreat} }
    enemies
  end
  
  def update_explosions args
    args.state.explosions.each do |explosion|
      explosion[:age]  += 0.5
      explosion[:path] = "sprites/explosion-#{explosion[:age].floor}.png"
    end
    args.state.explosions = args.state.explosions.reject { |explosion| explosion[:age] >= 7 }
  end
  
  def update_enemy_positions args
    args.state.enemies.each do |enemy|
      if enemy[:move_state] == :normal
        enemy[:x]          = args.state.columns[enemy[:col]]
        enemy[:y]          = args.state.rows[enemy[:row]]
        enemy[:move_state] = :dive if Math.rand < 0.0002 + 0.00005 * args.state.wave && args.state.player[:alive]
      elsif enemy[:move_state] == :dive
        enemy[:target_x] ||= args.state.player[:x]
        enemy[:target_y] ||= args.state.player[:y]
        dx               = enemy[:target_x] - enemy[:x]
        dy               = enemy[:target_y] - enemy[:y]
        vel              = Math.sqrt(dx * dx + dy * dy)
        speed_limit      = 2 + args.state.wave_root
        if vel > speed_limit
          dx /= vel / speed_limit
          dy /= vel / speed_limit
        end
        if vel < 1 || !args.state.player[:alive]
          enemy[:move_state] = :retreat
        end
        enemy[:x] += dx
        enemy[:y] += dy
      elsif enemy[:move_state] == :retreat
        enemy[:target_x] = args.state.columns[enemy[:col]]
        enemy[:target_y] = args.state.rows[enemy[:row]]
        dx               = enemy[:target_x] - enemy[:x]
        dy               = enemy[:target_y] - enemy[:y]
        vel              = Math.sqrt(dx * dx + dy * dy)
        speed_limit      = 2 + args.state.wave_root
        if vel > speed_limit
          dx /= vel / speed_limit
          dy /= vel / speed_limit
        elsif vel < 1
          enemy[:move_state] = :normal
          enemy[:target_x]   = nil
          enemy[:target_y]   = nil
        end
        enemy[:x] += dx
        enemy[:y] += dy
      end
    end
  end

#+end_src

*** Arcade - Dueling Starships - main.rb
#+begin_src ruby
  # ./samples/99_genre_arcade/dueling_starships/app/main.rb
  class DuelingSpaceships
    attr_accessor :state, :inputs, :outputs, :grid
  
    def tick
      defaults
      render
      calc
      input
    end
  
    def defaults
      outputs.background_color = [0, 0, 0]
      state.ship_blue       ||= new_blue_ship
      state.ship_red        ||= new_red_ship
      state.flames          ||= []
      state.bullets         ||= []
      state.ship_blue_score ||= 0
      state.ship_red_score  ||= 0
      state.stars           ||= 100.map do
        [rand.add(2).to_square(grid.w_half.randomize(:sign, :ratio),
                               grid.h_half.randomize(:sign, :ratio)),
         128 + 128.randomize(:ratio), 255, 255]
      end
    end
  
    def default_ship x, y, angle, sprite_path, bullet_sprite_path, color
      state.new_entity(:ship,
                      { x: x,
                        y: y,
                        dy: 0,
                        dx: 0,
                        damage: 0,
                        dead: false,
                        angle: angle,
                        max_alpha: 255,
                        sprite_path: sprite_path,
                        bullet_sprite_path: bullet_sprite_path,
                        color: color })
    end
  
    def new_red_ship
      default_ship(400, 250.randomize(:sign, :ratio),
                   180, 'sprites/ship_red.png', 'sprites/red_bullet.png',
                   [255, 90, 90])
    end
  
    def new_blue_ship
      default_ship(-400, 250.randomize(:sign, :ratio),
                   0, 'sprites/ship_blue.png', 'sprites/blue_bullet.png',
                   [110, 140, 255])
    end
  
    def render
      render_instructions
      render_score
      render_universe
      render_flames
      render_ships
      render_bullets
    end
  
    def render_ships
      update_ship_outputs(state.ship_blue)
      update_ship_outputs(state.ship_red)
      outputs.sprites << [state.ship_blue.sprite, state.ship_red.sprite]
      outputs.labels  << [state.ship_blue.label, state.ship_red.label]
    end
  
    def render_instructions
      return if state.ship_blue.dx  > 0  || state.ship_blue.dy > 0  ||
                state.ship_red.dx   > 0  || state.ship_red.dy  > 0  ||
                state.flames.length > 0
  
      outputs.labels << [grid.left.shift_right(30),
                         grid.bottom.shift_up(30),
                         "Two gamepads needed to play. R1 to accelerate. Left and right on D-PAD to turn ship. Hold A to shoot. Press B to drop mines.",
                         0, 0, 255, 255, 255]
    end
  
    def calc
      calc_thrusts
      calc_ships
      calc_bullets
      calc_winner
    end
  
    def input
      input_accelerate
      input_turn
      input_bullets_and_mines
    end
  
    def render_score
      outputs.labels << [grid.left.shift_right(80),
                         grid.top.shift_down(40),
                         state.ship_blue_score, 30, 1, state.ship_blue.color]
  
      outputs.labels << [grid.right.shift_left(80),
                         grid.top.shift_down(40),
                         state.ship_red_score,  30, 1, state.ship_red.color]
    end
  
    def render_universe
      return if outputs.static_solids.any?
      outputs.static_solids << grid.rect
      outputs.static_solids << state.stars
    end
  
    def apply_round_finished_alpha entity
      return entity unless state.round_finished_debounce
      entity.a *= state.round_finished_debounce.percentage_of(2.seconds)
      return entity
    end
  
    def update_ship_outputs ship, sprite_size = 66
      ship.sprite =
        apply_round_finished_alpha [sprite_size.to_square(ship.x, ship.y),
                                    ship.sprite_path,
                                    ship.angle,
                                    ship.dead ? 0 : 255 * ship.created_at.ease(2.seconds)].sprite
      ship.label =
        apply_round_finished_alpha [ship.x,
                                    ship.y + 100,
                                    "." * 5.minus(ship.damage).greater(0), 20, 1, ship.color, 255].label
    end
  
    def render_flames sprite_size = 6
      outputs.sprites << state.flames.map do |p|
        apply_round_finished_alpha [sprite_size.to_square(p.x, p.y),
                                    'sprites/flame.png', 0,
                                    p.max_alpha * p.created_at.ease(p.lifetime, :flip)].sprite
      end
    end
  
    def render_bullets sprite_size = 10
      outputs.sprites << state.bullets.map do |b|
        apply_round_finished_alpha [b.sprite_size.to_square(b.x, b.y),
                                    b.owner.bullet_sprite_path,
                                    0, b.max_alpha].sprite
      end
    end
  
    def wrap_location! location
      location.x = grid.left    if location.x > grid.right
      location.x = grid.right   if location.x < grid.left
      location.y = grid.top     if location.y < grid.bottom
      location.y = grid.bottom  if location.y > grid.top
      location
    end
  
    def calc_thrusts
      state.flames =
        state.flames
          .reject(&:old?)
          .map do |p|
            p.speed *= 0.9
            p.y += p.angle.vector_y(p.speed)
            p.x += p.angle.vector_x(p.speed)
            wrap_location! p
        end
    end
  
    def all_ships
      [state.ship_blue, state.ship_red]
    end
  
    def alive_ships
      all_ships.reject { |s| s.dead }
    end
  
    def calc_bullet bullet
      bullet.y += bullet.angle.vector_y(bullet.speed)
      bullet.x += bullet.angle.vector_x(bullet.speed)
      wrap_location! bullet
      explode_bullet! bullet if bullet.old?
      return if bullet.exploded
      return if state.round_finished
      alive_ships.each do |s|
        if s != bullet.owner &&
           s.sprite.intersect_rect?(bullet.sprite_size.to_square(bullet.x, bullet.y))
          explode_bullet! bullet, 10, 5, 30
          s.damage += 1
        end
      end
    end
  
    def calc_bullets
      state.bullets.each    { |b| calc_bullet b }
      state.bullets.reject! { |b| b.exploded }
    end
  
    def create_explosion! type, entity, flame_count, max_speed, lifetime, max_alpha = 255
      flame_count.times do
        state.flames << state.new_entity(type,
                                       { angle: 360.randomize(:ratio),
                                         speed: max_speed.randomize(:ratio),
                                         lifetime: lifetime,
                                         x: entity.x,
                                         y: entity.y,
                                         max_alpha: max_alpha })
      end
    end
  
    def explode_bullet! bullet, flame_override = 5, max_speed = 5, lifetime = 10
      bullet.exploded = true
      create_explosion! :bullet_explosion,
                        bullet,
                        flame_override,
                        max_speed,
                        lifetime,
                        bullet.max_alpha
    end
  
    def calc_ship ship
      ship.x += ship.dx
      ship.y += ship.dy
      wrap_location! ship
    end
  
    def calc_ships
      all_ships.each { |s| calc_ship s }
      return if all_ships.any? { |s| s.dead }
      return if state.round_finished
      return unless state.ship_blue.sprite.intersect_rect?(state.ship_red.sprite)
      state.ship_blue.damage = 5
      state.ship_red.damage  = 5
    end
  
    def create_thruster_flames! ship
      state.flames << state.new_entity(:ship_thruster,
                                     { angle: ship.angle + 180 + 60.randomize(:sign, :ratio),
                                       speed: 5.randomize(:ratio),
                                       max_alpha: 255 * ship.created_at_elapsed.percentage_of(2.seconds),
                                       lifetime: 30,
                                       x: ship.x - ship.angle.vector_x(40) + 5.randomize(:sign, :ratio),
                                       y: ship.y - ship.angle.vector_y(40) + 5.randomize(:sign, :ratio) })
    end
  
    def input_accelerate_ship should_move_ship, ship
      return if ship.dead
  
      should_move_ship &&= (ship.dx + ship.dy).abs < 5
  
      if should_move_ship
        create_thruster_flames! ship
        ship.dx += ship.angle.vector_x 0.050
        ship.dy += ship.angle.vector_y 0.050
      else
        ship.dx *= 0.99
        ship.dy *= 0.99
      end
    end
  
    def input_accelerate
      input_accelerate_ship inputs.controller_one.key_held.r1 || inputs.keyboard.up, state.ship_blue
      input_accelerate_ship inputs.controller_two.key_held.r1, state.ship_red
    end
  
    def input_turn_ship direction, ship
      ship.angle -= 3 * direction
    end
  
    def input_turn
      input_turn_ship inputs.controller_one.left_right + inputs.keyboard.left_right, state.ship_blue
      input_turn_ship inputs.controller_two.left_right, state.ship_red
    end
  
    def input_bullet create_bullet, ship
      return unless create_bullet
      return if ship.dead
  
      state.bullets << state.new_entity(:ship_bullet,
                                      { owner: ship,
                                        angle: ship.angle,
                                        max_alpha: 255 * ship.created_at_elapsed.percentage_of(2.seconds),
                                        speed: 5 + ship.dx.mult(ship.angle.vector_x) + ship.dy.mult(ship.angle.vector_y),
                                        lifetime: 120,
                                        sprite_size: 10,
                                        x: ship.x + ship.angle.vector_x * 32,
                                        y: ship.y + ship.angle.vector_y * 32 })
    end
  
    def input_mine create_mine, ship
      return unless create_mine
      return if ship.dead
  
      state.bullets << state.new_entity(:ship_bullet,
                                      { owner: ship,
                                        angle: 360.randomize(:sign, :ratio),
                                        max_alpha: 255 * ship.created_at_elapsed.percentage_of(2.seconds),
                                        speed: 0.02,
                                        sprite_size: 10,
                                        lifetime: 600,
                                        x: ship.x + ship.angle.vector_x * -50,
                                        y: ship.y + ship.angle.vector_y * -50 })
    end
  
    def input_bullets_and_mines
      return if state.bullets.length > 100
  
      [
        [inputs.controller_one.key_held.a || inputs.keyboard.key_held.space,
         inputs.controller_one.key_down.b || inputs.keyboard.key_down.down,
         state.ship_blue],
        [inputs.controller_two.key_held.a, inputs.controller_two.key_down.b, state.ship_red]
      ].each do |a_held, b_down, ship|
        input_bullet(a_held && state.tick_count.mod_zero?(10).or(a_held == 0), ship)
        input_mine(b_down, ship)
      end
    end
  
    def calc_kill_ships
      alive_ships.find_all { |s| s.damage >= 5 }.each do |s|
        s.dead = true
        create_explosion! :ship_explosion, s, 20, 20, 30, s.max_alpha
      end
    end
  
    def calc_score
      return if state.round_finished
      return if alive_ships.length > 1
  
      if alive_ships.first == state.ship_red
        state.ship_red_score += 1
      elsif alive_ships.first == state.ship_blue
        state.ship_blue_score += 1
      end
  
      state.round_finished = true
    end
  
    def calc_reset_ships
      return unless state.round_finished
      state.round_finished_debounce ||= 2.seconds
      state.round_finished_debounce -= 1
      return if state.round_finished_debounce > 0
      start_new_round!
    end
  
    def start_new_round!
      state.ship_blue = new_blue_ship
      state.ship_red  = new_red_ship
      state.round_finished = false
      state.round_finished_debounce = nil
      state.flames.clear
      state.bullets.clear
    end
  
    def calc_winner
      calc_kill_ships
      calc_score
      calc_reset_ships
    end
  end
  
  $dueling_spaceship = DuelingSpaceships.new
  
  def tick args
    args.grid.origin_center!
    $dueling_spaceship.inputs  = args.inputs
    $dueling_spaceship.outputs = args.outputs
    $dueling_spaceship.state    = args.state
    $dueling_spaceship.grid    = args.grid
    $dueling_spaceship.tick
  end

#+end_src

*** arcade/flappy dragon/credits.txt
#+begin_src ruby
  # ./samples/99_genre_arcade/flappy_dragon/CREDITS.txt
  code: Amir Rajan, https://twitter.com/amirrajan
  graphics and audio: Nick Culbertson, https://twitter.com/MobyPixel
  

#+end_src

*** arcade/flappy dragon/main.rb
#+begin_src ruby
  # ./samples/99_genre_arcade/flappy_dragon/app/main.rb
  class FlappyDragon
    attr_accessor :grid, :inputs, :state, :outputs
  
    def tick
      defaults
      render
      calc
      process_inputs
    end
  
    def defaults
      state.flap_power              = 11
      state.gravity                 = 0.9
      state.ceiling                 = 600
      state.ceiling_flap_power      = 6
      state.wall_countdown_length   = 100
      state.wall_gap_size           = 100
      state.wall_countdown        ||= 0
      state.hi_score              ||= 0
      state.score                 ||= 0
      state.walls                 ||= []
      state.x                     ||= 50
      state.y                     ||= 500
      state.dy                    ||= 0
      state.scene                 ||= :menu
      state.scene_at              ||= 0
      state.difficulty            ||= :normal
      state.new_difficulty        ||= :normal
      state.countdown             ||= 4.seconds
      state.flash_at              ||= 0
    end
  
    def render
      outputs.sounds << "sounds/flappy-song.ogg" if state.tick_count == 1
      render_score
      render_menu
      render_game
    end
  
    def render_score
      outputs.primitives << { x: 10, y: 710, text: "HI SCORE: #{state.hi_score}", **large_white_typeset }
      outputs.primitives << { x: 10, y: 680, text: "SCORE: #{state.score}", **large_white_typeset }
      outputs.primitives << { x: 10, y: 650, text: "DIFFICULTY: #{state.difficulty.upcase}", **large_white_typeset }
    end
  
    def render_menu
      return unless state.scene == :menu
      render_overlay
  
      outputs.labels << { x: 640, y: 700, text: "Flappy Dragon", size_enum: 50, alignment_enum: 1, **white }
      outputs.labels << { x: 640, y: 500, text: "Instructions: Press Spacebar to flap. Don't die.", size_enum: 4, alignment_enum: 1, **white }
      outputs.labels << { x: 430, y: 430, text: "[Tab]    Change difficulty", size_enum: 4, alignment_enum: 0, **white }
      outputs.labels << { x: 430, y: 400, text: "[Enter]  Start at New Difficulty ", size_enum: 4, alignment_enum: 0, **white }
      outputs.labels << { x: 430, y: 370, text: "[Escape] Cancel/Resume ", size_enum: 4, alignment_enum: 0, **white }
      outputs.labels << { x: 640, y: 300, text: "(mouse, touch, and game controllers work, too!) ", size_enum: 4, alignment_enum: 1, **white }
      outputs.labels << { x: 640, y: 200, text: "Difficulty: #{state.new_difficulty.capitalize}", size_enum: 4, alignment_enum: 1, **white }
  
      outputs.labels << { x: 10, y: 100, text: "Code:   @amirrajan",     **white }
      outputs.labels << { x: 10, y:  80, text: "Art:    @mobypixel",     **white }
      outputs.labels << { x: 10, y:  60, text: "Music:  @mobypixel",     **white }
      outputs.labels << { x: 10, y:  40, text: "Engine: DragonRuby GTK", **white }
    end
  
    def render_overlay
      overlay_rect = grid.rect.scale_rect(1.1, 0, 0)
      outputs.primitives << { x: overlay_rect.x,
                              y: overlay_rect.y,
                              w: overlay_rect.w,
                              h: overlay_rect.h,
                              r: 0, g: 0, b: 0, a: 230 }.solid!
    end
  
    def render_game
      render_game_over
      render_background
      render_walls
      render_dragon
      render_flash
    end
  
    def render_game_over
      return unless state.scene == :game
      outputs.labels << { x: 638, y: 358, text: score_text,     size_enum: 20, alignment_enum: 1 }
      outputs.labels << { x: 635, y: 360, text: score_text,     size_enum: 20, alignment_enum: 1, r: 255, g: 255, b: 255 }
      outputs.labels << { x: 638, y: 428, text: countdown_text, size_enum: 20, alignment_enum: 1 }
      outputs.labels << { x: 635, y: 430, text: countdown_text, size_enum: 20, alignment_enum: 1, r: 255, g: 255, b: 255 }
    end
  
    def render_background
      outputs.sprites << { x: 0, y: 0, w: 1280, h: 720, path: 'sprites/background.png' }
  
      scroll_point_at   = state.tick_count
      scroll_point_at   = state.scene_at if state.scene == :menu
      scroll_point_at   = state.death_at if state.countdown > 0
      scroll_point_at ||= 0
  
      outputs.sprites << scrolling_background(scroll_point_at, 'sprites/parallax_back.png',   0.25)
      outputs.sprites << scrolling_background(scroll_point_at, 'sprites/parallax_middle.png', 0.50)
      outputs.sprites << scrolling_background(scroll_point_at, 'sprites/parallax_front.png',  1.00, -80)
    end
  
    def scrolling_background at, path, rate, y = 0
      [
        { x:    0 - at.*(rate) % 1440, y: y, w: 1440, h: 720, path: path },
        { x: 1440 - at.*(rate) % 1440, y: y, w: 1440, h: 720, path: path }
      ]
    end
  
    def render_walls
      state.walls.each do |w|
        w.sprites = [
          { x: w.x, y: w.bottom_height - 720, w: 100, h: 720, path: 'sprites/wall.png',       angle: 180 },
          { x: w.x, y: w.top_y,               w: 100, h: 720, path: 'sprites/wallbottom.png', angle: 0 }
        ]
      end
      outputs.sprites << state.walls.map(&:sprites)
    end
  
    def render_dragon
      state.show_death = true if state.countdown == 3.seconds
  
      if state.show_death == false || !state.death_at
        animation_index = state.flapped_at.frame_index 6, 2, false if state.flapped_at
        sprite_name = "sprites/dragon_fly#{animation_index.or(0) + 1}.png"
        state.dragon_sprite = { x: state.x, y: state.y, w: 100, h: 80, path: sprite_name, angle: state.dy * 1.2 }
      else
        sprite_name = "sprites/dragon_die.png"
        state.dragon_sprite = { x: state.x, y: state.y, w: 100, h: 80, path: sprite_name, angle: state.dy * 1.2 }
        sprite_changed_elapsed    = state.death_at.elapsed_time - 1.seconds
        state.dragon_sprite.angle += (sprite_changed_elapsed ** 1.3) * state.death_fall_direction * -1
        state.dragon_sprite.x     += (sprite_changed_elapsed ** 1.2) * state.death_fall_direction
        state.dragon_sprite.y     += (sprite_changed_elapsed * 14 - sprite_changed_elapsed ** 1.6)
      end
  
      outputs.sprites << state.dragon_sprite
    end
  
    def render_flash
      return unless state.flash_at
  
      outputs.primitives << { **grid.rect.to_hash,
                              **white,
                              a: 255 * state.flash_at.ease(20, :flip) }.solid!
  
      state.flash_at = 0 if state.flash_at.elapsed_time > 20
    end
  
    def calc
      return unless state.scene == :game
      reset_game if state.countdown == 1
      state.countdown -= 1 and return if state.countdown > 0
      calc_walls
      calc_flap
      calc_game_over
    end
  
    def calc_walls
      state.walls.each { |w| w.x -= 8 }
  
      walls_count_before_removal = state.walls.length
  
      state.walls.reject! { |w| w.x < -100 }
  
      state.score += 1 if state.walls.count < walls_count_before_removal
  
      state.wall_countdown -= 1 and return if state.wall_countdown > 0
  
      state.walls << state.new_entity(:wall) do |w|
        w.x             = grid.right
        w.opening       = grid.top
                              .randomize(:ratio)
                              .greater(200)
                              .lesser(520)
        w.bottom_height = w.opening - state.wall_gap_size
        w.top_y         = w.opening + state.wall_gap_size
      end
  
      state.wall_countdown = state.wall_countdown_length
    end
  
    def calc_flap
      state.y += state.dy
      state.dy = state.dy.lesser state.flap_power
      state.dy -= state.gravity
      return if state.y < state.ceiling
      state.y  = state.ceiling
      state.dy = state.dy.lesser state.ceiling_flap_power
    end
  
    def calc_game_over
      return unless game_over?
  
      state.death_at = state.tick_count
      state.death_from = state.walls.first
      state.death_fall_direction = -1
      state.death_fall_direction =  1 if state.x > state.death_from.x
      outputs.sounds << "sounds/hit-sound.wav"
      begin_countdown
    end
  
    def process_inputs
      process_inputs_menu
      process_inputs_game
    end
  
    def process_inputs_menu
      return unless state.scene == :menu
  
      changediff = inputs.keyboard.key_down.tab || inputs.controller_one.key_down.select
      if inputs.mouse.click
        p = inputs.mouse.click.point
        if (p.y >= 165) && (p.y < 200) && (p.x >= 500) && (p.x < 800)
          changediff = true
        end
      end
  
      if changediff
        case state.new_difficulty
        when :easy
          state.new_difficulty = :normal
        when :normal
          state.new_difficulty = :hard
        when :hard
          state.new_difficulty = :flappy
        when :flappy
          state.new_difficulty = :easy
        end
      end
  
      if inputs.keyboard.key_down.enter || inputs.controller_one.key_down.start || inputs.controller_one.key_down.a
        state.difficulty = state.new_difficulty
        change_to_scene :game
        reset_game false
        state.hi_score = 0
        begin_countdown
      end
  
      if inputs.keyboard.key_down.escape || (inputs.mouse.click && !changediff) || inputs.controller_one.key_down.b
        state.new_difficulty = state.difficulty
        change_to_scene :game
      end
    end
  
    def process_inputs_game
      return unless state.scene == :game
  
      clicked_menu = false
      if inputs.mouse.click
        p = inputs.mouse.click.point
        clicked_menu = (p.y >= 620) && (p.x < 275)
      end
  
      if clicked_menu || inputs.keyboard.key_down.escape || inputs.keyboard.key_down.enter || inputs.controller_one.key_down.start
        change_to_scene :menu
      elsif (inputs.mouse.down || inputs.mouse.click || inputs.keyboard.key_down.space || inputs.controller_one.key_down.a) && state.countdown == 0
        state.dy = 0
        state.dy += state.flap_power
        state.flapped_at = state.tick_count
        outputs.sounds << "sounds/fly-sound.wav"
      end
    end
  
    def white
      { r: 255, g: 255, b: 255 }
    end
  
    def large_white_typeset
      { size_enum: 5, alignment_enum: 0, r: 255, g: 255, b: 255 }
    end
  
    def at_beginning?
      state.walls.count == 0
    end
  
    def dragon_collision_box
      state.dragon_sprite
           .scale_rect(1.0 - collision_forgiveness, 0.5, 0.5)
           .rect_shift_right(10)
           .rect_shift_up(state.dy * 2)
    end
  
    def game_over?
      return true if state.y <= 0.-(500 * collision_forgiveness) && !at_beginning?
  
      state.walls
          .flat_map { |w| w.sprites }
          .any? do |s|
            s && s.intersect_rect?(dragon_collision_box)
          end
    end
  
    def collision_forgiveness
      case state.difficulty
      when :easy
        0.9
      when :normal
        0.7
      when :hard
        0.5
      when :flappy
        0.3
      else
        0.9
      end
    end
  
    def countdown_text
      state.countdown ||= -1
      return ""          if state.countdown == 0
      return "GO!"       if state.countdown.idiv(60) == 0
      return "GAME OVER" if state.death_at
      return "READY?"
    end
  
    def begin_countdown
      state.countdown = 4.seconds
    end
  
    def score_text
      return ""                        unless state.countdown > 1.seconds
      return ""                        unless state.death_at
      return "SCORE: 0 (LOL)"          if state.score == 0
      return "HI SCORE: #{state.score}" if state.score == state.hi_score
      return "SCORE: #{state.score}"
    end
  
    def reset_game set_flash = true
      state.flash_at = state.tick_count if set_flash
      state.walls = []
      state.y = 500
      state.dy = 0
      state.hi_score = state.hi_score.greater(state.score)
      state.score = 0
      state.wall_countdown = state.wall_countdown_length.fdiv(2)
      state.show_death = false
      state.death_at = nil
    end
  
    def change_to_scene scene
      state.scene = scene
      state.scene_at = state.tick_count
      inputs.keyboard.clear
      inputs.controller_one.clear
    end
  end
  
  $flappy_dragon = FlappyDragon.new
  
  def tick args
    $flappy_dragon.grid = args.grid
    $flappy_dragon.inputs = args.inputs
    $flappy_dragon.state = args.state
    $flappy_dragon.outputs = args.outputs
    $flappy_dragon.tick
  end

#+end_src

*** Arcade - Pong - main.rb
#+begin_src ruby
  # ./samples/99_genre_arcade/pong/app/main.rb
  def tick args
    defaults args
    render args
    calc args
    input args
  end
  
  def defaults args
    args.state.ball.debounce       ||= 3 * 60
    args.state.ball.size           ||= 10
    args.state.ball.size_half      ||= args.state.ball.size / 2
    args.state.ball.x              ||= 640
    args.state.ball.y              ||= 360
    args.state.ball.dx             ||= 5.randomize(:sign)
    args.state.ball.dy             ||= 5.randomize(:sign)
    args.state.left_paddle.y       ||= 360
    args.state.right_paddle.y      ||= 360
    args.state.paddle.h            ||= 120
    args.state.paddle.w            ||= 10
    args.state.left_paddle.score   ||= 0
    args.state.right_paddle.score  ||= 0
  end
  
  def render args
    render_center_line args
    render_scores args
    render_countdown args
    render_ball args
    render_paddles args
    render_instructions args
  end
  
  begin :render_methods
    def render_center_line args
      args.outputs.lines  << [640, 0, 640, 720]
    end
  
    def render_scores args
      args.outputs.labels << [
        [320, 650, args.state.left_paddle.score, 10, 1],
        [960, 650, args.state.right_paddle.score, 10, 1]
      ]
    end
  
    def render_countdown args
      return unless args.state.ball.debounce > 0
      args.outputs.labels << [640, 360, "%.2f" % args.state.ball.debounce.fdiv(60), 10, 1]
    end
  
    def render_ball args
      args.outputs.solids << solid_ball(args)
    end
  
    def render_paddles args
      args.outputs.solids << solid_left_paddle(args)
      args.outputs.solids << solid_right_paddle(args)
    end
  
    def render_instructions args
      args.outputs.labels << [320, 30, "W and S keys to move left paddle.",  0, 1]
      args.outputs.labels << [920, 30, "O and L keys to move right paddle.", 0, 1]
    end
  end
  
  def calc args
    args.state.ball.debounce -= 1 and return if args.state.ball.debounce > 0
    calc_move_ball args
    calc_collision_with_left_paddle args
    calc_collision_with_right_paddle args
    calc_collision_with_walls args
  end
  
  begin :calc_methods
    def calc_move_ball args
      args.state.ball.x += args.state.ball.dx
      args.state.ball.y += args.state.ball.dy
    end
  
    def calc_collision_with_left_paddle args
      if solid_left_paddle(args).intersect_rect? solid_ball(args)
        args.state.ball.dx *= -1
      elsif args.state.ball.x < 0
        args.state.right_paddle.score += 1
        calc_reset_round args
      end
    end
  
    def calc_collision_with_right_paddle args
      if solid_right_paddle(args).intersect_rect? solid_ball(args)
        args.state.ball.dx *= -1
      elsif args.state.ball.x > 1280
        args.state.left_paddle.score += 1
        calc_reset_round args
      end
    end
  
    def calc_collision_with_walls args
      if args.state.ball.y + args.state.ball.size_half > 720
        args.state.ball.y = 720 - args.state.ball.size_half
        args.state.ball.dy *= -1
      elsif args.state.ball.y - args.state.ball.size_half < 0
        args.state.ball.y = args.state.ball.size_half
        args.state.ball.dy *= -1
      end
    end
  
    def calc_reset_round args
      args.state.ball.x = 640
      args.state.ball.y = 360
      args.state.ball.dx = 5.randomize(:sign)
      args.state.ball.dy = 5.randomize(:sign)
      args.state.ball.debounce = 3 * 60
    end
  end
  
  def input args
    input_left_paddle args
    input_right_paddle args
  end
  
  begin :input_methods
    def input_left_paddle args
      if args.inputs.controller_one.key_down.down  || args.inputs.keyboard.key_down.s
        args.state.left_paddle.y -= 40
      elsif args.inputs.controller_one.key_down.up || args.inputs.keyboard.key_down.w
        args.state.left_paddle.y += 40
      end
    end
  
    def input_right_paddle args
      if args.inputs.controller_two.key_down.down  || args.inputs.keyboard.key_down.l
        args.state.right_paddle.y -= 40
      elsif args.inputs.controller_two.key_down.up || args.inputs.keyboard.key_down.o
        args.state.right_paddle.y += 40
      end
    end
  end
  
  begin :assets
    def solid_ball args
      centered_rect args.state.ball.x, args.state.ball.y, args.state.ball.size, args.state.ball.size
    end
  
    def solid_left_paddle args
      centered_rect_vertically 0, args.state.left_paddle.y, args.state.paddle.w, args.state.paddle.h
    end
  
    def solid_right_paddle args
      centered_rect_vertically 1280 - args.state.paddle.w, args.state.right_paddle.y, args.state.paddle.w, args.state.paddle.h
    end
  
    def centered_rect x, y, w, h
      [x - w / 2, y - h / 2, w, h]
    end
  
    def centered_rect_vertically x, y, w, h
      [x, y - h / 2, w, h]
    end
  end

#+end_src

*** Arcade - Snakemoji - main.rb
#+begin_src ruby
  # ./samples/99_genre_arcade/snakemoji/app/main.rb
  # coding: utf-8
  ################################
  #  So I was working on a snake game while
  #  learning DragonRuby, and at some point I had a thought
  #  what if I use "😀" as a function name, surely it wont work right...?
  #  RIGHT....?
  #  BUT IT DID, IT WORKED
  #  it all went downhill from then
  #  Created by Anton K. (ai Doge)
  #  https://gist.github.com/scorp200
  #############LICENSE############
  #  Feel free to use this anywhere and however you want
  #  You can sell this to EA for $1,000,000 if you want, its completely free.
  #  Just rememeber you are helping this... thing... to spread...
  #  ALSO! I am not liable for any mental, physical or financial damage caused.
  #############LICENSE############
  
  
  class Array
    #Helper function
    def move! vector
      self.x += vector.x
      self.y += vector.y
      return self
    end
  
    #Helper function to draw snake body
    def draw! 🎮, 📺, color
      translate 📺.solids, 🎮.⛓, [self.x * 🎮.⚖️ + 🎮.🛶 / 2, self.y * 🎮.⚖️ + 🎮.🛶 / 2, 🎮.⚖️ - 🎮.🛶, 🎮.⚖️ - 🎮.🛶, color]
    end
  
    #This is where it all started, I was trying to find  good way to multiply a map by a number, * is already used so is **
    #I kept trying different combinations of symbols, when suddenly...
    def 😀 value
      self.map {|d| d * value}
    end
  end
  
  #Draw stuff with an offset
  def translate output_collection, ⛓, what
    what.x += ⛓.x
    what.y += ⛓.y
    output_collection << what
  end
  
  BLUE = [33, 150, 243]
  RED = [244, 67, 54]
  GOLD = [255, 193, 7]
  LAST = 0
  
  def tick args
    defaults args.state
    render args.state, args.outputs
    input args.state, args.inputs
    update args.state
  end
  
  def update 🎮
    #Update every 10 frames
    if 🎮.tick_count.mod_zero? 10
      #Add new snake body piece at head's location
      🎮.🐍 << [*🎮.🤖]
      #Assign Next Direction to Direction
      🎮.🚗 = *🎮.🚦
  
      #Trim the snake a bit if its longer than current size
      if 🎮.🐍.length > 🎮.🛒
        🎮.🐍 = 🎮.🐍[-🎮.🛒..-1]
      end
  
      #Move the head in the Direction
      🎮.🤖.move! 🎮.🚗
  
      #If Head is outside the playing field, or inside snake's body restart game
      if 🎮.🤖.x < 0 || 🎮.🤖.x >= 🎮.🗺.x || 🎮.🤖.y < 0 || 🎮.🤖.y >= 🎮.🗺.y || 🎮.🚗 != [0, 0] && 🎮.🐍.any? {|s| s == 🎮.🤖}
        LAST = 🎮.💰
        🎮.as_hash.clear
        return
      end
  
      #If head lands on food add size and score
      if 🎮.🤖 == 🎮.🍎
        🎮.🛒 += 1
        🎮.💰 += (🎮.🛒 * 0.8).floor.to_i + 5
        spawn_🍎 🎮
        puts 🎮.🍎
      end
    end
  
    #Every second remove 1 point
    if 🎮.💰 > 0 && 🎮.tick_count.mod_zero?(60)
      🎮.💰 -= 1
    end
  end
  
  def spawn_🍎 🎮
    #Food
    🎮.🍎 ||= [*🎮.🤖]
    #Randomly spawns food inside the playing field, keep doing this if the food keeps landing on the snake's body
    while 🎮.🐍.any? {|s| s == 🎮.🍎} || 🎮.🍎 == 🎮.🤖 do
      🎮.🍎 = [rand(🎮.🗺.x), rand(🎮.🗺.y)]
    end
  end
  
  def render 🎮, 📺
    #Paint the background black
    📺.solids << [0, 0, 1280, 720, 0, 0, 0, 255]
    #Draw a border for the playing field
    translate 📺.borders, 🎮.⛓, [0, 0, 🎮.🗺.x * 🎮.⚖️, 🎮.🗺.y * 🎮.⚖️, 255, 255, 255]
  
    #Draw the snake's body
    🎮.🐍.map do |🐍| 🐍.draw! 🎮, 📺, BLUE end
    #Draw the head
    🎮.🤖.draw! 🎮, 📺, BLUE
    #Draw the food
    🎮.🍎.draw! 🎮, 📺, RED
  
    #Draw current score
    translate 📺.labels, 🎮.⛓, [5, 715, "Score: #{🎮.💰}", GOLD]
    #Draw your last score, if any
    translate 📺.labels, 🎮.⛓, [[*🎮.🤖.😀(🎮.⚖️)].move!([0, 🎮.⚖️ * 2]), "Your Last score is #{LAST}", 0, 1, GOLD] unless LAST == 0 || 🎮.🚗 != [0, 0]
    #Draw starting message, only if Direction is 0
    translate 📺.labels, 🎮.⛓, [🎮.🤖.😀(🎮.⚖️), "Press any Arrow key to start", 0, 1, GOLD] unless 🎮.🚗 != [0, 0]
  end
  
  def input 🎮, 🕹
    #Left and Right keyboard input, only change if X direction is 0
    if 🕹.keyboard.key_held.left && 🎮.🚗.x == 0
      🎮.🚦 = [-1, 0]
    elsif 🕹.keyboard.key_held.right && 🎮.🚗.x == 0
      🎮.🚦 = [1, 0]
    end
  
    #Up and Down keyboard input, only change if Y direction is 0
    if 🕹.keyboard.key_held.up && 🎮.🚗.y == 0
      🎮.🚦 = [0, 1]
    elsif 🕹.keyboard.key_held.down && 🎮.🚗.y == 0
      🎮.🚦 = [0, -1]
    end
  end
  
  def defaults 🎮
    #Playing field size
    🎮.🗺 ||= [20, 20]
    #Scale for drawing, screen height / Field height
    🎮.⚖️ ||= 720 / 🎮.🗺.y
    #Offset, offset all rendering to the center of the screen
    🎮.⛓ ||= [(1280 - 720).fdiv(2), 0]
    #Padding, make the snake body slightly smaller than the scale
    🎮.🛶 ||= (🎮.⚖️ * 0.2).to_i
    #Snake Size
    🎮.🛒 ||= 3
    #Snake head, the only part we are actually controlling
    🎮.🤖 ||= [🎮.🗺.x / 2, 🎮.🗺.y / 2]
    #Snake body map, follows the head
    🎮.🐍 ||= []
    #Direction the head moves to
    🎮.🚗 ||= [0, 0]
    #Next_Direction, during input check only change this variable and then when game updates asign this to Direction
    🎮.🚦 ||= [*🎮.🚗]
    #Your score
    🎮.💰 ||= 0
    #Spawns Food randomly
    spawn_🍎(🎮) unless 🎮.🍎?
  end

#+end_src

*** Arcade - Solar System - main.rb
#+begin_src ruby
  # ./samples/99_genre_arcade/solar_system/app/main.rb
  # Focused tutorial video: https://s3.amazonaws.com/s3.dragonruby.org/dragonruby-nddnug-workshop.mp4
  # Workshop/Presentation which provides motivation for creating a game engine: https://www.youtube.com/watch?v=S3CFce1arC8
  
  def defaults args
    args.outputs.background_color = [0, 0, 0]
    args.state.x ||= 640
    args.state.y ||= 360
    args.state.stars ||= 100.map do
      [1280 * rand, 720 * rand, rand.fdiv(10), 255 * rand, 255 * rand, 255 * rand]
    end
  
    args.state.sun ||= args.state.new_entity(:sun) do |s|
      s.s = 100
      s.path = 'sprites/sun.png'
    end
  
    args.state.planets = [
      [:mercury,   65,  5,          88],
      [:venus,    100, 10,         225],
      [:earth,    120, 10,         365],
      [:mars,     140,  8,         687],
      [:jupiter,  280, 30, 365 *  11.8],
      [:saturn,   350, 20, 365 *  29.5],
      [:uranus,   400, 15, 365 *    84],
      [:neptune,  440, 15, 365 * 164.8],
      [:pluto,    480,  5, 365 * 247.8],
    ].map do |name, distance, size, year_in_days|
      args.state.new_entity(name) do |p|
        p.path = "sprites/#{name}.png"
        p.distance = distance * 0.7
        p.s = size * 0.7
        p.year_in_days = year_in_days
      end
    end
  
    args.state.ship ||= args.state.new_entity(:ship) do |s|
      s.x = 1280 * rand
      s.y = 720 * rand
      s.angle = 0
    end
  end
  
  def to_sprite args, entity
    x = 0
    y = 0
  
    if entity.year_in_days
      day = args.state.tick_count
      day_in_year = day % entity.year_in_days
      entity.random_start_day ||= day_in_year * rand
      percentage_of_year = day_in_year.fdiv(entity.year_in_days)
      angle = 365 * percentage_of_year
      x = angle.vector_x(entity.distance)
      y = angle.vector_y(entity.distance)
    end
  
    [640 + x - entity.s.half, 360 + y - entity.s.half, entity.s, entity.s, entity.path]
  end
  
  def render args
    args.outputs.solids << [0, 0, 1280, 720]
  
    args.outputs.sprites << args.state.stars.map do |x, y, _, r, g, b|
      [x, y, 10, 10, 'sprites/star.png', 0, 100, r, g, b]
    end
  
    args.outputs.sprites << to_sprite(args, args.state.sun)
    args.outputs.sprites << args.state.planets.map { |p| to_sprite args, p }
    args.outputs.sprites << [args.state.ship.x, args.state.ship.y, 20, 20, 'sprites/ship.png', args.state.ship.angle]
  end
  
  def calc args
    args.state.stars = args.state.stars.map do |x, y, speed, r, g, b|
      x += speed
      y += speed
      x = 0 if x > 1280
      y = 0 if y > 720
      [x, y, speed, r, g, b]
    end
  
    if args.state.tick_count == 0
      args.outputs.sounds << 'sounds/bg.ogg'
    end
  end
  
  def process_inputs args
    if args.inputs.keyboard.left || args.inputs.controller_one.key_held.left
      args.state.ship.angle += 1
    elsif args.inputs.keyboard.right || args.inputs.controller_one.key_held.right
      args.state.ship.angle -= 1
    end
  
    if args.inputs.keyboard.up || args.inputs.controller_one.key_held.a
      args.state.ship.x += args.state.ship.angle.x_vector
      args.state.ship.y += args.state.ship.angle.y_vector
    end
  end
  
  def tick args
    defaults args
    render args
    calc args
    process_inputs args
  end
  
  def r
    $gtk.reset
  end

#+end_src

*** Arcade - Sound Golf - main.rb
#+begin_src ruby
  # ./samples/99_genre_arcade/sound_golf/app/main.rb
  =begin
  
   APIs Listing that haven't been encountered in previous sample apps:
  
   - sample: Chooses random element from array.
     In this sample app, the target note is set by taking a sample from the collection
     of available notes.
  
   Reminders:
   - args.grid.(left|right|top|bottom): Pixel value for the boundaries of the virtual
     720 p screen (Dragon Ruby Game Toolkits's virtual resolution is always 1280x720).
  
   - args.state.new_entity: Used when we want to create a new object, like a sprite or button.
     For example, if we want to create a new button, we would declare it as a new entity and
     then define its properties.
  
   - String interpolation: Uses #{} syntax; everything between the #{ and the } is evaluated
     as Ruby code, and the placeholder is replaced with its corresponding value or result.
  
   - args.outputs.labels: An array. The values generate a label.
     The parameters are [X, Y, TEXT, SIZE, ALIGNMENT, RED, GREEN, BLUE, ALPHA, FONT STYLE]
     For more information about labels, go to mygame/documentation/02-labels.md.
  
   - find_all: Finds all elements from a collection that meet a certain requirements (and excludes the ones that don't).
  
   - first: Returns the first element of an array.
  
   - inside_rect: Returns true or false depending on if the point is inside the rect.
  
   - to_sym: Returns symbol corresponding to string. Will create a symbol if it does
     not already exist.
  
  =end
  
  # This sample app allows users to test their musical skills by matching the piano sound that plays in each
  # level to the correct note.
  
  # Runs all the methods necessary for the game to function properly.
  def tick args
    defaults args
    render args
    calc args
    input_mouse args
    tick_instructions args, "Sample app shows how to play sounds. args.outputs.sounds << \"path_to_wav.wav\""
  end
  
  # Sets default values and creates empty collections
  # Initialization happens in the first frame only
  def defaults args
    args.state.notes ||= []
    args.state.click_feedbacks ||= []
    args.state.current_level ||= 1
    args.state.times_wrong ||= 0 # when game starts, user hasn't guessed wrong yet
  end
  
  # Uses a label to display current level, and shows the score
  # Creates a button to play the sample note, and displays the available notes that could be a potential match
  def render args
  
    # grid.w_half positions the label in the horizontal center of the screen.
    args.outputs.labels << [args.grid.w_half, args.grid.top.shift_down(40), "Hole #{args.state.current_level} of 9", 0, 1, 0, 0, 0]
  
    render_score args # shows score on screen
  
    args.state.play_again_button ||= { x: 560, y: args.grid.h * 3 / 4 - 40, w: 160, h: 60, label: 'again' } # array definition, text/title
    args.state.play_note_button ||= { x: 560, y: args.grid.h * 3 / 4 - 40, w: 160, h: 60, label: 'play' }
  
    if args.state.game_over # if game is over, a "play again" button is shown
      # Calculations ensure that Play Again label is displayed in center of border
      # Remove calculations from y parameters and see what happens to border and label placement
      args.outputs.labels <<  [args.grid.w_half, args.grid.h * 3 / 4, "Play Again", 0, 1, 0, 0, 0] # outputs label
      args.outputs.borders << args.state.play_again_button # outputs border
    else # otherwise, if game is not over
      # Calculations ensure that label appears in center of border
      args.outputs.labels <<  [args.grid.w_half, args.grid.h * 3 / 4, "Play Note ##{args.state.current_level}", 0, 1, 0, 0, 0] # outputs label
      args.outputs.borders << args.state.play_note_button # outputs border
    end
  
    return if args.state.game_over # return if game is over
  
    args.outputs.labels <<   [args.grid.w_half, 400, "I think the note is a(n)...",  0, 1, 0, 0, 0] # outputs label
  
    # Shows all of the available notes that can be potential matches.
    available_notes.each_with_index do |note, i|
      args.state.notes[i] ||= piano_button(args, note, i + 1) # calls piano_button method on each note (creates label and border)
      args.outputs.labels <<   args.state.notes[i].label # outputs note on screen with a label and a border
      args.outputs.borders <<  args.state.notes[i].border
    end
  
    # Shows whether or not the user is correct by filling the screen with either red or green
    args.outputs.solids << args.state.click_feedbacks.map { |c| c.solid }
  end
  
  # Shows the score (number of times the user guesses wrong) onto the screen using labels.
  def render_score args
    if args.state.times_wrong == 0 # if the user has guessed wrong zero times, the score is par
      args.outputs.labels << [args.grid.w_half, args.grid.top.shift_down(80), "Score: PAR", 0, 1, 0, 0, 0]
    else # otherwise, number of times the user has guessed wrong is shown
      args.outputs.labels << [args.grid.w_half, args.grid.top.shift_down(80), "Score: +#{args.state.times_wrong}", 0, 1, 0, 0, 0] # shows score using string interpolation
    end
  end
  
  # Sets the target note for the level and performs calculations on click_feedbacks.
  def calc args
    args.state.target_note ||= available_notes.sample # chooses a note from available_notes collection as target note
    args.state.click_feedbacks.each    { |c| c.solid[-1] -= 5 } # remove this line and solid color will remain on screen indefinitely
    # comment this line out and the solid color will keep flashing on screen instead of being removed from click_feedbacks collection
    args.state.click_feedbacks.reject! { |c| c.solid[-1] <= 0 }
  end
  
  # Uses input from the user to play the target note, as well as the other notes that could be a potential match.
  def input_mouse args
    return unless args.inputs.mouse.click # return unless the mouse is clicked
  
    # finds button that was clicked by user
    button_clicked = args.outputs.borders.find_all do |b| # go through borders collection to find all borders that meet requirements
      args.inputs.mouse.click.point.inside_rect? b # find button border that mouse was clicked inside of
    end.find_all { |b| b.is_a? Hash }.first # reject, return first element
  
    return unless button_clicked # return unless button_clicked as a value (a button was clicked)
  
    queue_click_feedback args, # calls queue_click_feedback method on the button that was clicked
                         button_clicked.x,
                         button_clicked.y,
                         button_clicked.w,
                         button_clicked.h,
                         150, 100, 200 # sets color of button to shade of purple
  
    if button_clicked[:label] == 'play' # if "play note" button is pressed
      args.outputs.sounds << "sounds/#{args.state.target_note}.wav" # sound of target note is output
    elsif button_clicked[:label] == 'again' # if "play game again" button is pressed
      args.state.target_note = nil # no target note
      args.state.current_level = 1 # starts at level 1 again
      args.state.times_wrong = 0 # starts off with 0 wrong guesses
      args.state.game_over = false # the game is not over (because it has just been restarted)
    else # otherwise if neither of those buttons were pressed
      args.outputs.sounds << "sounds/#{button_clicked[:label]}.wav" # sound of clicked note is played
      if button_clicked[:label] == args.state.target_note # if clicked note is target note
        args.state.target_note = nil # target note is emptied
  
        if args.state.current_level < 9 # if game hasn't reached level 9
          args.state.current_level += 1 # game goes to next level
        else # otherwise, if game has reached level 9
          args.state.game_over = true # the game is over
        end
  
        queue_click_feedback args, 0, 0, args.grid.w, args.grid.h, 100, 200, 100 # green shown if user guesses correctly
      else # otherwise, if clicked note is not target note
        args.state.times_wrong += 1 # increments times user guessed wrong
        queue_click_feedback args, 0, 0, args.grid.w, args.grid.h, 200, 100, 100 # red shown is user guesses wrong
      end
    end
  end
  
  # Creates a collection of all of the available notes as symbols
  def available_notes
    [:C3, :D3, :E3, :F3, :G3, :A3, :B3, :C4]
  end
  
  # Creates buttons for each note, and sets a label (the note's name) and border for each note's button.
  def piano_button args, note, position
    args.state.new_entity(:button) do |b| # declares button as new entity
      b.label  =  [460 + 40.mult(position), args.grid.h * 0.4, "#{note}", 0, 1, 0, 0, 0] # label definition
      b.border =  { x: 460 + 40.mult(position) - 20, y: args.grid.h * 0.4 - 32, w: 40, h: 40, label: note } # border definition, text/title; 20 subtracted so label is in center of border
    end
  end
  
  # Color of click feedback changes depending on what button was clicked, and whether the guess is right or wrong
  # If a button is clicked, the inside of button is purple (see input_mouse method)
  # If correct note is clicked, screen turns green
  # If incorrect note is clicked, screen turns red (again, see input_mouse method)
  def queue_click_feedback args, x, y, w, h, *color
    args.state.click_feedbacks << args.state.new_entity(:click_feedback) do |c| # declares feedback as new entity
      c.solid =  [x, y, w, h, *color, 255] # sets color
    end
  end
  
  def tick_instructions args, text, y = 715
    return if args.state.key_event_occurred
    if args.inputs.mouse.click ||
       args.inputs.keyboard.directional_vector ||
       args.inputs.keyboard.key_down.enter ||
       args.inputs.keyboard.key_down.escape
      args.state.key_event_occurred = true
    end
  
    args.outputs.debug << [0, y - 50, 1280, 60].solid
    args.outputs.debug << [640, y, text, 1, 1, 255, 255, 255].label
    args.outputs.debug << [640, y - 25, "(click to dismiss instructions)" , -2, 1, 255, 255, 255].label
  end

#+end_src

*** Arcade - Twinstick - main.rb
#+begin_src ruby
  # ./samples/99_genre_arcade/twinstick/app/main.rb
  def tick args
    args.state.player         ||= {x: 600, y: 320, w: 80, h: 80, path: 'sprites/circle-white.png', vx: 0, vy: 0, health: 10, cooldown: 0, score: 0}
    args.state.enemies        ||= []
    args.state.player_bullets ||= []
    args.state.tick_count     ||= -1
    args.state.tick_count     += 1
    spawn_enemies args
    kill_enemies args
    move_enemies args
    move_bullets args
    move_player args
    fire_player args
    args.state.player[:r] = args.state.player[:g] = args.state.player[:b] = (args.state.player[:health] * 25.5).clamp(0, 255)
    label_color           = args.state.player[:health] <= 5 ? 255 : 0
    args.outputs.labels << [
        {
            x: args.state.player.x + 40, y: args.state.player.y + 60, alignment_enum: 1, text: "#{args.state.player[:health]} HP",
            r: label_color, g: label_color, b: label_color
        }, {
            x: args.state.player.x + 40, y: args.state.player.y + 40, alignment_enum: 1, text: "#{args.state.player[:score]} PTS",
            r: label_color, g: label_color, b: label_color, size_enum: 2 - args.state.player[:score].to_s.length,
        }
    ]
    args.outputs.sprites << [args.state.player, args.state.enemies, args.state.player_bullets]
    args.state.clear! if args.state.player[:health] < 0 # Reset the game if the player's health drops below zero
  end
  
  def spawn_enemies args
    # Spawn enemies more frequently as the player's score increases.
    if rand < (100+args.state.player[:score])/(10000 + args.state.player[:score]) || args.state.tick_count.zero?
      theta = rand * Math::PI * 2
      args.state.enemies << {
          x: 600 + Math.cos(theta) * 800, y: 320 + Math.sin(theta) * 800, w: 80, h: 80, path: 'sprites/circle-white.png',
          r: (256 * rand).floor, g: (256 * rand).floor, b: (256 * rand).floor
      }
    end
  end
  
  def kill_enemies args
    args.state.enemies.reject! do |enemy|
      # Check if enemy and player are within 80 pixels of each other (i.e. overlapping)
      if 6400 > (enemy.x - args.state.player.x) ** 2 + (enemy.y - args.state.player.y) ** 2
        # Enemy is touching player. Kill enemy, and reduce player HP by 1.
        args.state.player[:health] -= 1
      else
        args.state.player_bullets.any? do |bullet|
          # Check if enemy and bullet are within 50 pixels of each other (i.e. overlapping)
          if 2500 > (enemy.x - bullet.x + 30) ** 2 + (enemy.y - bullet.y + 30) ** 2
            # Increase player health by one for each enemy killed by a bullet after the first enemy, up to a maximum of 10 HP
            args.state.player[:health] += 1 if args.state.player[:health] < 10 && bullet[:kills] > 0
            # Keep track of how many enemies have been killed by this particular bullet
            bullet[:kills]             += 1
            # Earn more points by killing multiple enemies with one shot.
            args.state.player[:score]  += bullet[:kills]
          end
        end
      end
    end
  end
  
  def move_enemies args
    args.state.enemies.each do |enemy|
      # Get the angle from the enemy to the player
      theta   = Math.atan2(enemy.y - args.state.player.y, enemy.x - args.state.player.x)
      # Convert the angle to a vector pointing at the player
      dx, dy  = theta.to_degrees.vector 5
      # Move the enemy towards thr player
      enemy.x -= dx
      enemy.y -= dy
    end
  end
  
  def move_bullets args
    args.state.player_bullets.each do |bullet|
      # Move the bullets according to the bullet's velocity
      bullet.x += bullet[:vx]
      bullet.y += bullet[:vy]
    end
    args.state.player_bullets.reject! do |bullet|
      # Despawn bullets that are outside the screen area
      bullet.x < -20 || bullet.y < -20 || bullet.x > 1300 || bullet.y > 740
    end
  end
  
  def move_player args
    # Get the currently held direction.
    dx, dy                 = move_directional_vector args
    # Take the weighted average of the old velocities and the desired velocities. 
    # Since move_directional_vector returns values between -1 and 1, 
    #   and we want to limit the speed to 7.5, we multiply dx and dy by 7.5*0.1 to get 0.75
    args.state.player[:vx] = args.state.player[:vx] * 0.9 + dx * 0.75
    args.state.player[:vy] = args.state.player[:vy] * 0.9 + dy * 0.75
    # Move the player
    args.state.player.x    += args.state.player[:vx]
    args.state.player.y    += args.state.player[:vy]
    # If the player is about to go out of bounds, put them back in bounds.
    args.state.player.x    = args.state.player.x.clamp(0, 1201)
    args.state.player.y    = args.state.player.y.clamp(0, 640)
  end
  
  
  def fire_player args
    # Reduce the firing cooldown each tick
    args.state.player[:cooldown] -= 1
    # If the player is allowed to fire
    if args.state.player[:cooldown] <= 0
      dx, dy = shoot_directional_vector args # Get the bullet velocity
      return if dx == 0 && dy == 0 # If the velocity is zero, the player doesn't want to fire. Therefore, we just return early.
      # Add a new bullet to the list of player bullets.
      args.state.player_bullets << {
          x:     args.state.player.x + 30 + 40 * dx,
          y:     args.state.player.y + 30 + 40 * dy,
          w:     20, h: 20,
          path:  'sprites/circle-white.png',
          r:     0, g: 0, b: 0,
          vx:    10 * dx + args.state.player[:vx] / 7.5, vy: 10 * dy + args.state.player[:vy] / 7.5, # Factor in a bit of the player's velocity
          kills: 0
      }
      args.state.player[:cooldown] = 30 # Reset the cooldown
    end
  end
  
  # Custom function for getting a directional vector just for movement using WASD
  def move_directional_vector args
    dx = 0
    dx += 1 if args.inputs.keyboard.d
    dx -= 1 if args.inputs.keyboard.a
    dy = 0
    dy += 1 if args.inputs.keyboard.w
    dy -= 1 if args.inputs.keyboard.s
    if dx != 0 && dy != 0
      dx *= 0.7071
      dy *= 0.7071
    end
    [dx, dy]
  end
  
  # Custom function for getting a directional vector just for shooting using the arrow keys
  def shoot_directional_vector args
    dx = 0
    dx += 1 if args.inputs.keyboard.key_down.right || args.inputs.keyboard.key_held.right
    dx -= 1 if args.inputs.keyboard.key_down.left || args.inputs.keyboard.key_held.left
    dy = 0
    dy += 1 if args.inputs.keyboard.key_down.up || args.inputs.keyboard.key_held.up
    dy -= 1 if args.inputs.keyboard.key_down.down || args.inputs.keyboard.key_held.down
    if dx != 0 && dy != 0
      dx *= 0.7071
      dy *= 0.7071
    end
    [dx, dy]
  end
#+end_src

*** Crafting - Craft Game Starting Point - main.rb
#+begin_src ruby
  # ./samples/99_genre_crafting/craft_game_starting_point/app/main.rb
  # ==================================================
  # A NOTE TO JAM CRAFT PARTICIPANTS:
  # The comments and code in here are just as small piece of DragonRuby's capabilities.
  # Be sure to check out the rest of the sample apps. Start with README.txt and go from there!
  # ==================================================
  
  # def tick args is the entry point into your game. This function is called at
  # a fixed update time of 60hz (60 fps).
  def tick args
    # The defaults function intitializes the game.
    defaults args
  
    # After the game is initialized, render it.
    render args
  
    # After rendering the player should be able to respond to input.
    input args
  
    # After responding to input, the game performs any additional calculations.
    calc args
  end
  
  def defaults args
    # hide the mouse cursor for this game, we are going to render our own cursor
    if args.state.tick_count == 0
      args.gtk.hide_cursor
    end
  
    args.state.click_ripples ||= []
  
    # everything is on a 1280x720 virtual canvas, so you can
    # hardcode locations
  
    # define the borders for where the inventory is located
    # args.state is a data structure that accepts any arbitrary parameters
    # so you can create an object graph without having to create any classes.
  
    # Bottom left is 0, 0. Top right is 1280, 720.
    # The inventory area is at the top of the screen
    # the number 80 is the size of all the sprites, so that is what is being
    # used to decide the with and height
    args.state.sprite_size = 80
  
    args.state.inventory_border.w  = args.state.sprite_size * 10
    args.state.inventory_border.h  = args.state.sprite_size * 3
    args.state.inventory_border.x  = 10
    args.state.inventory_border.y  = 710 - args.state.inventory_border.h
  
    # define the borders for where the crafting area is located
    # the crafting area is below the inventory area
    # the number 80 is the size of all the sprites, so that is what is being
    # used to decide the with and height
    args.state.craft_border.x =  10
    args.state.craft_border.y = 220
    args.state.craft_border.w = args.state.sprite_size * 3
    args.state.craft_border.h = args.state.sprite_size * 3
  
    # define the area where results are located
    # the crafting result is to the right of the craft area
    args.state.result_border.x =  10 + args.state.sprite_size * 3 + args.state.sprite_size
    args.state.result_border.y = 220 + args.state.sprite_size
    args.state.result_border.w = args.state.sprite_size
    args.state.result_border.h = args.state.sprite_size
  
    # initialize items for the first time if they are nil
    # you start with 15 wood, 1 chest, and 5 plank
    # Ruby has built in syntax for dictionaries (they look a lot like json objects).
    # Ruby also has a special type called a Symbol denoted with a : followed by a word.
    # Symbols are nice because they remove the need for magic strings.
    if !args.state.items
      args.state.items = [
        {
          id: :wood, # :wood is a Symbol, this is better than using "wood" for the id
          quantity: 15,
          path: 'sprites/wood.png',
          location: :inventory,
          ordinal_x: 0, ordinal_y: 0
        },
        {
          id: :chest,
          quantity: 1,
          path: 'sprites/chest.png',
          location: :inventory,
          ordinal_x: 1, ordinal_y: 0
        },
        {
          id: :plank,
          quantity: 5,
          path: 'sprites/plank.png',
          location: :inventory,
          ordinal_x: 2, ordinal_y: 0
        },
      ]
  
      # after initializing the oridinal positions, derive the pixel
      # locations assuming that the width and height are 80
      args.state.items.each { |item| set_inventory_position args, item }
    end
  
    # define all the oridinal positions of the inventory slots
    if !args.state.inventory_area
      args.state.inventory_area = [
        { ordinal_x: 0,  ordinal_y: 0 },
        { ordinal_x: 1,  ordinal_y: 0 },
        { ordinal_x: 2,  ordinal_y: 0 },
        { ordinal_x: 3,  ordinal_y: 0 },
        { ordinal_x: 4,  ordinal_y: 0 },
        { ordinal_x: 5,  ordinal_y: 0 },
        { ordinal_x: 6,  ordinal_y: 0 },
        { ordinal_x: 7,  ordinal_y: 0 },
        { ordinal_x: 8,  ordinal_y: 0 },
        { ordinal_x: 9,  ordinal_y: 0 },
        { ordinal_x: 0,  ordinal_y: 1 },
        { ordinal_x: 1,  ordinal_y: 1 },
        { ordinal_x: 2,  ordinal_y: 1 },
        { ordinal_x: 3,  ordinal_y: 1 },
        { ordinal_x: 4,  ordinal_y: 1 },
        { ordinal_x: 5,  ordinal_y: 1 },
        { ordinal_x: 6,  ordinal_y: 1 },
        { ordinal_x: 7,  ordinal_y: 1 },
        { ordinal_x: 8,  ordinal_y: 1 },
        { ordinal_x: 9,  ordinal_y: 1 },
        { ordinal_x: 0,  ordinal_y: 2 },
        { ordinal_x: 1,  ordinal_y: 2 },
        { ordinal_x: 2,  ordinal_y: 2 },
        { ordinal_x: 3,  ordinal_y: 2 },
        { ordinal_x: 4,  ordinal_y: 2 },
        { ordinal_x: 5,  ordinal_y: 2 },
        { ordinal_x: 6,  ordinal_y: 2 },
        { ordinal_x: 7,  ordinal_y: 2 },
        { ordinal_x: 8,  ordinal_y: 2 },
        { ordinal_x: 9,  ordinal_y: 2 },
      ]
  
      # after initializing the oridinal positions, derive the pixel
      # locations assuming that the width and height are 80
      args.state.inventory_area.each { |i| set_inventory_position args, i }
  
      # if you want to see the result you can use the Ruby function called "puts".
      # Uncomment this line to see the value.
      # puts args.state.inventory_area
  
      # You can see all things written via puts in DragonRuby's Console, or under logs/log.txt.
      # To bring up DragonRuby's Console, press the ~ key within the game.
    end
  
    # define all the oridinal positions of the craft slots
    if !args.state.craft_area
      args.state.craft_area = [
        { ordinal_x: 0, ordinal_y: 0 },
        { ordinal_x: 0, ordinal_y: 1 },
        { ordinal_x: 0, ordinal_y: 2 },
        { ordinal_x: 1, ordinal_y: 0 },
        { ordinal_x: 1, ordinal_y: 1 },
        { ordinal_x: 1, ordinal_y: 2 },
        { ordinal_x: 2, ordinal_y: 0 },
        { ordinal_x: 2, ordinal_y: 1 },
        { ordinal_x: 2, ordinal_y: 2 },
      ]
  
      # after initializing the oridinal positions, derive the pixel
      # locations assuming that the width and height are 80
      args.state.craft_area.each { |c| set_craft_position args, c }
    end
  end
  
  
  def render args
    # for the results area, create a sprite that show its boundaries
    args.outputs.primitives << { x: args.state.result_border.x,
                                 y: args.state.result_border.y,
                                 w: args.state.result_border.w,
                                 h: args.state.result_border.h,
                                 path: 'sprites/border-black.png' }
  
    # for each inventory spot, create a sprite
    # args.outputs.primitives is how DragonRuby performs a render.
    # Adding a single hash or multiple hashes to this array will tell
    # DragonRuby to render those primitives on that frame.
  
    # The .map function on Array is used instead of any kind of looping.
    # .map returns a new object for every object within an Array.
    args.outputs.primitives << args.state.inventory_area.map do |a|
      { x: a.x, y: a.y, w: a.w, h: a.h, path: 'sprites/border-black.png' }
    end
  
    # for each craft spot, create a sprite
    args.outputs.primitives << args.state.craft_area.map do |a|
      { x: a.x, y: a.y, w: a.w, h: a.h, path: 'sprites/border-black.png' }
    end
  
    # after the borders have been rendered, render the
    # items within those slots (and allow for highlighting)
    # if an item isn't currently being held
    allow_inventory_highlighting = !args.state.held_item
  
    # go through each item and render them
    # use Array's find_all method to remove any items that are currently being held
    args.state.items.find_all { |item| item[:location] != :held }.map do |item|
      # if an item is currently being held, don't render it in it's spot within the
      # inventory or craft area (this is handled via the find_all method).
  
      # the item_prefab returns a hash containing all the visual components of an item.
      # the main sprite, the black background, the quantity text, and a hover indication
      # if the mouse is currently hovering over the item.
      args.outputs.primitives << item_prefab(args, item, allow_inventory_highlighting, args.inputs.mouse)
    end
  
    # The last thing we want to render is the item currently being held.
    args.outputs.primitives << item_prefab(args, args.state.held_item, allow_inventory_highlighting, args.inputs.mouse)
  
    args.outputs.primitives << args.state.click_ripples
  
    # render a mouse cursor since we have the OS cursor hidden
    args.outputs.primitives << { x: args.inputs.mouse.x - 5, y: args.inputs.mouse.y - 5, w: 10, h: 10, path: 'sprites/circle-gray.png', a: 128 }
  end
  
  # Alrighty! This is where all the fun happens
  def input args
    # if the mouse is clicked and not item is currently being held
    # args.state.held_item is nil when the game starts.
    # If the player clicks, the property args.inputs.mouse.click will
    # be a non nil value, we don't want to process any of the code here
    # if the mouse hasn't been clicked
    return if !args.inputs.mouse.click
  
    # if a click occurred, add a ripple to the ripple queue
    args.state.click_ripples << { x: args.inputs.mouse.x - 5, y: args.inputs.mouse.y - 5, w: 10, h: 10, path: 'sprites/circle-gray.png', a: 128 }
  
    # if the mouse has been clicked, and no item is currently held...
    if !args.state.held_item
      # see if any of the items intersect the pointer using the inside_rect? method
      # the find method will either return the first object that returns true
      # for the match clause, or it'll return nil if nothing matches the match clause
      found = args.state.items.find do |item|
        # for each item in args.state.items, run the following boolean check
        args.inputs.mouse.click.point.inside_rect?(item)
      end
  
      # if an item intersects the mouse pointer, then set the item's location to :held and
      # set args.state.held_item to the item for later reference
      if found
        args.state.held_item = found
        found[:location] = :held
      end
  
    # if the mouse is clicked and an item is currently beign held....
    elsif args.state.held_item
      # determine if a slot within the craft area was clicked
      craft_area = args.state.craft_area.find { |a| args.inputs.mouse.click.point.inside_rect? a }
  
      # also determine if a slot within the inventory area was clicked
      inventory_area = args.state.inventory_area.find { |a| args.inputs.mouse.click.point.inside_rect? a }
  
      # if the click was within a craft area
      if craft_area
        # check to see if an item is already there and ignore the click if an item is found
        # item_at_craft_slot is a helper method that returns an item or nil for a given oridinal
        # position
        item_already_there = item_at_craft_slot args, craft_area[:ordinal_x], craft_area[:ordinal_y]
  
        # if an item *doesn't* exist in the craft area
        if !item_already_there
          # if the quantity they are currently holding is greater than 1
          if args.state.held_item[:quantity] > 1
            # remove one item (creating a seperate item of the same type), and place it
            # at the oridinal position and location of the craft area
            # the .merge method on Hash creates a new Hash, but updates any values
            # passed as arguments to merge
            new_item = args.state.held_item.merge(quantity: 1,
                                                  location: :craft,
                                                  ordinal_x: craft_area[:ordinal_x],
                                                  ordinal_y: craft_area[:ordinal_y])
  
            # after the item is crated, place it into the args.state.items collection
            args.state.items << new_item
  
            # then subtract one from the held item
            args.state.held_item[:quantity] -= 1
  
          # if the craft area is available and there is only one item being held
          elsif args.state.held_item[:quantity] == 1
            # instead of creating any new items just set the location of the held item
            # to the oridinal position of the craft area, and then nil out the
            # held item state so that a new item can be picked up
            args.state.held_item[:location] = :craft
            args.state.held_item[:ordinal_x] = craft_area[:ordinal_x]
            args.state.held_item[:ordinal_y] = craft_area[:ordinal_y]
            args.state.held_item = nil
          end
        end
  
      # if the selected area is an inventory area (as opposed to within the craft area)
      elsif inventory_area
  
        # check to see if there is already an item in that inventory slot
        # the item_at_inventory_slot helper method returns an item or nil
        item_already_there = item_at_inventory_slot args, inventory_area[:ordinal_x], inventory_area[:ordinal_y]
  
        # if there is already an item there, and the item types/id match
        if item_already_there && item_already_there[:id] == args.state.held_item[:id]
          # then merge the item quantities
          held_quantity = args.state.held_item[:quantity]
          item_already_there[:quantity] += held_quantity
  
          # remove the item being held from the items collection (since it's quantity is now 0)
          args.state.items.reject! { |i| i[:location] == :held }
  
          # nil out the held_item so a new item can be picked up
          args.state.held_item = nil
  
        # if there currently isn't an item there, then put the held item in the slot
        elsif !item_already_there
          args.state.held_item[:location] = :inventory
          args.state.held_item[:ordinal_x] = inventory_area[:ordinal_x]
          args.state.held_item[:ordinal_y] = inventory_area[:ordinal_y]
  
          # nil out the held_item so a new item can be picked up
          args.state.held_item = nil
        end
      end
    end
  end
  
  # the calc method is executed after input
  def calc args
    # make sure that the real position of the inventory
    # items are updated every frame to ensure that they
    # are placed correctly given their location and oridinal positions
    # instead of using .map, here we use .each (since we are not returning a new item and just updating the items in place)
    args.state.items.each do |item|
      # based on the location of the item, invoke the correct pixel conversion method
      if item[:location] == :inventory
        set_inventory_position args, item
      elsif item[:location] == :craft
        set_craft_position args, item
      elsif item[:location] == :held
        # if the item is held, center the item around the mouse pointer
        args.state.held_item.x = args.inputs.mouse.x - args.state.held_item.w.half
        args.state.held_item.y = args.inputs.mouse.y - args.state.held_item.h.half
      end
    end
  
    # for each hash/sprite in the click ripples queue,
    # expand its size by 20 percent and decrease its alpha
    # by 10.
    args.state.click_ripples.each do |ripple|
      delta_w = ripple.w * 1.2 - ripple.w
      delta_h = ripple.h * 1.2 - ripple.h
      ripple.x -= delta_w.half
      ripple.y -= delta_h.half
      ripple.w += delta_w
      ripple.h += delta_h
      ripple.a -= 10
    end
  
    # remove any items from the collection where the alpha value is less than equal to
    # zero using the reject! method (reject with an exclamation point at the end changes the
    # array value in place, while reject without the exclamation point returns a new array).
    args.state.click_ripples.reject! { |ripple| ripple.a <= 0 }
  end
  
  # helper function for finding an item at a craft slot
  def item_at_craft_slot args, ordinal_x, ordinal_y
    args.state.items.find { |i| i[:location] == :craft && i[:ordinal_x] == ordinal_x && i[:ordinal_y] == ordinal_y }
  end
  
  # helper function for finding an item at an inventory slot
  def item_at_inventory_slot args, ordinal_x, ordinal_y
    args.state.items.find { |i| i[:location] == :inventory && i[:ordinal_x] == ordinal_x && i[:ordinal_y] == ordinal_y }
  end
  
  # helper function that creates a visual representation of an item
  def item_prefab args, item, should_highlight, mouse
    return nil unless item
  
    overlay = nil
  
    x = item.x
    y = item.y
    w = item.w
    h = item.h
  
    if should_highlight && mouse.point.inside_rect?(item)
      overlay = { x: x, y: y, w: w, h: h, path: "sprites/square-blue.png", a: 130, }
    end
  
    [
      # sprites are hashes with a path property, this is the main sprite
      { x: x,      y: y, w: args.state.sprite_size, h: args.state.sprite_size, path: item[:path], },
  
      # this represents the black area in the bottom right corner of the main sprite so that the
      # quantity is visible
      { x: x + 55, y: y, w: 25, h: 25, path: "sprites/square-black.png", }, # sprites are hashes with a path property
  
      # labels are hashes with a text property
      { x: x + 56, y: y + 22, text: "#{item[:quantity]}", r: 255, g: 255, b: 255, },
  
      # this is the mouse overlay, if the overlay isn't applicable, then this value will be nil (nil values will not be rendered)
      overlay
    ]
  end
  
  # helper function for deriving the position of an item within inventory
  def set_inventory_position args, item
    item.x = args.state.inventory_border.x + item[:ordinal_x] * 80
    item.y = (args.state.inventory_border.y + args.state.inventory_border.h - 80) - item[:ordinal_y] * 80
    item.w = 80
    item.h = 80
  end
  
  # helper function for deriving the position of an item within the craft area
  def set_craft_position args, item
    item.x = args.state.craft_border.x + item[:ordinal_x] * 80
    item.y = (args.state.craft_border.y + args.state.inventory_border.h - 80) - item[:ordinal_y] * 80
    item.w = 80
    item.h = 80
  end
  
  # Any lines outside of a function will be executed when the file is reloaded.
  # So every time you save main.rb, the game will be reset.
  # Comment out the line below if you don't want this to happen.
  $gtk.reset

#+end_src

*** Crafting - Farming Game Starting Point - main.rb
#+begin_src ruby
  # ./samples/99_genre_crafting/farming_game_starting_point/app/main.rb
  def tick args
    args.state.tile_size     = 80
    args.state.player_speed  = 4
    args.state.player      ||= tile(args, 7, 3, 0, 128, 180)
    generate_map args
    #press j to plant a green onion
    if args.inputs.keyboard.j
    #change this part you can change what you want to plant
     args.state.walls << tile(args, ((args.state.player.x+80)/args.state.tile_size), ((args.state.player.y)/args.state.tile_size), 255, 255, 255)
     args.state.plants << tile(args, ((args.state.player.x+80)/args.state.tile_size), ((args.state.player.y+80)/args.state.tile_size), 0, 160, 0)
    end
    # Adds walls, background, and player to args.outputs.solids so they appear on screen
    args.outputs.solids << [0,0,1280,720, 237,189,101]
    args.outputs.sprites << [0, 0, 1280, 720, 'sprites/background.png']
    args.outputs.solids << args.state.walls
    args.outputs.solids << args.state.player
    args.outputs.solids << args.state.plants
    args.outputs.labels << [320, 640, "press J to plant", 3, 1, 255, 0, 0, 200]
  
    move_player args, -1,  0 if args.inputs.keyboard.left # x position decreases by 1 if left key is pressed
    move_player args,  1,  0 if args.inputs.keyboard.right # x position increases by 1 if right key is pressed
    move_player args,  0,  1 if args.inputs.keyboard.up # y position increases by 1 if up is pressed
    move_player args,  0, -1 if args.inputs.keyboard.down # y position decreases by 1 if down is pressed
  end
  
  # Sets position, size, and color of the tile
  def tile args, x, y, *color
    [x * args.state.tile_size, # sets definition for array using method parameters
     y * args.state.tile_size, # multiplying by tile_size sets x and y to correct position using pixel values
     args.state.tile_size,
     args.state.tile_size,
     *color]
  end
  
  # Creates map by adding tiles to the wall, as well as a goal (that the player needs to reach)
  def generate_map args
    return if args.state.area
  
    # Creates the area of the map. There are 9 rows running horizontally across the screen
    # and 16 columns running vertically on the screen. Any spot with a "1" is not
    # open for the player to move into (and is green), and any spot with a "0" is available
    # for the player to move in.
    args.state.area = [
      [1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,],
      [1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1,],
      [1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1,],
      [1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1,],
      [1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1,],
      [1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1,],
      [1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1,],
      [1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,],
      [1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1 ],
    ].reverse # reverses the order of the area collection
  
    # By reversing the order, the way that the area appears above is how it appears
    # on the screen in the game. If we did not reverse, the map would appear inverted.
  
    #The wall starts off with no tiles.
    args.state.walls = []
    args.state.plants = []
  
    # If v is 1, a green tile is added to args.state.walls.
    # If v is 2, a black tile is created as the goal.
    args.state.area.map_2d do |y, x, v|
      if    v == 1
        args.state.walls << tile(args, x, y, 255, 160, 156) # green tile
      end
    end
  end
  
  # Allows the player to move their box around the screen
  def move_player args, *vector
    box = args.state.player.shift_rect(vector) # box is able to move at an angle
  
    # If the player's box hits a wall, it is not able to move further in that direction
    return if args.state.walls
                  .any_intersect_rect?(box)
  
    # Player's box is able to move at angles (not just the four general directions) fast
    args.state.player =
      args.state.player
          .shift_rect(vector.x * args.state.player_speed, # if we don't multiply by speed, then
                      vector.y * args.state.player_speed) # the box will move extremely slow
  end

#+end_src

*** Crafting - Farming Game Starting Point - tests.rb
#+begin_src ruby
  # ./samples/99_genre_crafting/farming_game_starting_point/app/tests.rb
  # For advanced users:

  # You can put some quick verification tests here, any method

  # that starts with the `test_` will be run when you save this file.

  

  # Here is an example test and game

  

  # To run the test: ./dragonruby mygame --eval app/tests.rb --no-tick

  

  class MySuperHappyFunGame

    attr_gtk

  

    def tick

      outputs.solids << [100, 100, 300, 300]

    end

  end

  

  def test_universe args, assert

    game = MySuperHappyFunGame.new

    game.args = args

    game.tick

    assert.true!  args.outputs.solids.length == 1, "failure: a solid was not added after tick"

    assert.false! 1 == 2, "failure: some how, 1 equals 2, the world is ending"

    puts "test_universe completed successfully"

  end

  

  puts "running tests"

  $gtk.reset 100

  $gtk.log_level = :off

  $gtk.tests.start


#+end_src

*** Dev Tools - Add Buttons To Console - main.rb
#+begin_src ruby
  # ./samples/99_genre_dev_tools/add_buttons_to_console/app/main.rb
  # You can customize the buttons that show up in the Console.
  class GTK::Console::Menu
    # STEP 1: Override the custom_buttons function.
    def custom_buttons
      [
        (button id: :yay,
                # row for button
                row: 3,
                # column for button
                col: 10,
                # text
                text: "I AM CUSTOM",
                # when clicked call the custom_button_clicked function
                method: :custom_button_clicked),
  
        (button id: :yay,
                # row for button
                row: 3,
                # column for button
                col: 9,
                # text
                text: "CUSTOM ALSO",
                # when clicked call the custom_button_also_clicked function
                method: :custom_button_also_clicked)
      ]
    end
  
    # STEP 2: Define the function that should be called.
    def custom_button_clicked
      log "* INFO: I AM CUSTOM was clicked!"
    end
  
    def custom_button_also_clicked
      log "* INFO: Custom Button Clicked at #{Kernel.global_tick_count}!"
  
      all_buttons_as_string = $gtk.console.menu.buttons.map do |b|
        <<-S.strip
  ** id: #{b[:id]}
  :PROPERTIES:
  :id:     :#{b[:id]}
  :method: :#{b[:method]}
  :text:   #{b[:text]}
  :END:
  S
      end.join("\n")
  
      log <<-S
  * INFO: Here are all the buttons:
  #{all_buttons_as_string}
  S
    end
  end
  
  def tick args
    args.outputs.labels << [args.grid.center.x, args.grid.center.y,
                            "Open the DragonRuby Console to see the custom menu items.",
                            0, 1]
  end

#+end_src

*** Dev Tools - Animation Creator Starting Point - main.rb
#+begin_src ruby
  # ./samples/99_genre_dev_tools/animation_creator_starting_point/app/main.rb
  class OneBitLowrezPaint
    attr_gtk
  
    def tick
      outputs.background_color = [0, 0, 0]
      defaults
      render_instructions
      render_canvas
      render_buttons_frame_selection
      render_animation_frame_thumbnails
      render_animation
      input_mouse_click
      input_keyboard
      calc_auto_export
      calc_buttons_frame_selection
      calc_animation_frames
      process_queue_create_sprite
      process_queue_reset_sprite
      process_queue_update_rt_animation_frame
    end
  
    def defaults
      state.animation_frames_per_second = 12
      queues.create_sprite ||= []
      queues.reset_sprite ||= []
      queues.update_rt_animation_frame ||= []
  
      if !state.animation_frames
        state.animation_frames ||= []
        add_animation_frame_to_end
      end
  
      state.last_mouse_down ||= 0
      state.last_mouse_up   ||= 0
  
      state.buttons_frame_selection.left = 10
      state.buttons_frame_selection.top  = grid.top - 10
      state.buttons_frame_selection.size = 20
  
      defaults_canvas_sprite
  
      state.edit_mode ||= :drawing
    end
  
    def defaults_canvas_sprite
      rt_canvas.size   = 16
      rt_canvas.zoom   = 30
      rt_canvas.width  = rt_canvas.size * rt_canvas.zoom
      rt_canvas.height = rt_canvas.size * rt_canvas.zoom
      rt_canvas.sprite = { x: 0,
                           y: 0,
                           w: rt_canvas.width,
                           h: rt_canvas.height,
                           path: :rt_canvas }.center_inside_rect(x: 0, y: 0, w: 640, h: 720)
  
      return unless state.tick_count == 1
  
      outputs[:rt_canvas].width      = rt_canvas.width
      outputs[:rt_canvas].height     = rt_canvas.height
      outputs[:rt_canvas].sprites   << (rt_canvas.size + 1).map_with_index do |x|
        (rt_canvas.size + 1).map_with_index do |y|
          path = 'sprites/square-white.png'
          path = 'sprites/square-blue.png' if x == 7 || x == 8
          { x: x * rt_canvas.zoom,
            y: y * rt_canvas.zoom,
            w: rt_canvas.zoom,
            h: rt_canvas.zoom,
            path: path,
            a: 50 }
        end
      end
    end
  
    def render_instructions
      instructions = [
        "* Hotkeys:",
        "- d: hold to erase, release to draw.",
        "- a: add frame.",
        "- c: copy frame.",
        "- v: paste frame.",
        "- x: delete frame.",
        "- b: go to previous frame.",
        "- f: go to next frame.",
        "- w: save to ./canvas directory.",
        "- l: load from ./canvas."
      ]
  
      instructions.each.with_index do |l, i|
        outputs.labels << { x: 840, y: 500 - (i * 20), text: "#{l}",
                            r: 180, g: 180, b: 180, size_enum: 0 }
      end
    end
  
    def render_canvas
      return if state.tick_count.zero?
      outputs.sprites << rt_canvas.sprite
    end
  
    def render_buttons_frame_selection
      args.outputs.primitives << state.buttons_frame_selection.items.map_with_index do |b, i|
        label = { x: b.x + state.buttons_frame_selection.size.half,
                  y: b.y,
                  text: "#{i + 1}", r: 180, g: 180, b: 180,
                  size_enum: -4, alignment_enum: 1 }.label!
  
        selection_border = b.merge(r: 40, g: 40, b: 40).border!
  
        if i == state.animation_frames_selected_index
          selection_border = b.merge(r: 40, g: 230, b: 200).border!
        end
  
        [selection_border, label]
      end
    end
  
    def render_animation_frame_thumbnails
      return if state.tick_count.zero?
  
      outputs[:current_animation_frame].width   = rt_canvas.size
      outputs[:current_animation_frame].height  = rt_canvas.size
      outputs[:current_animation_frame].solids <<  selected_animation_frame[:pixels].map_with_index do |f, i|
        { x: f.x,
          y: f.y,
          w: 1,
          h: 1, r: 255, g: 255, b: 255 }
      end
  
      outputs.sprites << rt_canvas.sprite.merge(path: :current_animation_frame)
  
      state.animation_frames.map_with_index do |animation_frame, animation_frame_index|
        outputs.sprites << state.buttons_frame_selection[:items][animation_frame_index][:inner_rect]
                                .merge(path: animation_frame[:rt_name])
      end
    end
  
    def render_animation
      sprite_index = 0.frame_index count: state.animation_frames.length,
                                   hold_for: 60 / state.animation_frames_per_second,
                                   repeat: true
  
      args.outputs.sprites << { x: 700 - 8,
                                y: 120,
                                w: 16,
                                h: 16,
                                path: (sprite_path sprite_index) }
  
      args.outputs.sprites << { x: 700 - 16,
                                y: 230,
                                w: 32,
                                h: 32,
                                path: (sprite_path sprite_index) }
  
      args.outputs.sprites << { x: 700 - 32,
                                y: 360,
                                w: 64,
                                h: 64,
                                path: (sprite_path sprite_index) }
  
      args.outputs.sprites << { x: 700 - 64,
                                y: 520,
                                w: 128,
                                h: 128,
                                path: (sprite_path sprite_index) }
    end
  
    def input_mouse_click
      if inputs.mouse.up
        state.last_mouse_up = state.tick_count
      elsif inputs.mouse.moved && user_is_editing?
        edit_current_animation_frame inputs.mouse.point
      end
  
      return unless inputs.mouse.click
  
      clicked_frame_button = state.buttons_frame_selection.items.find do |b|
        inputs.mouse.point.inside_rect? b
      end
  
      if (clicked_frame_button)
        state.animation_frames_selected_index = clicked_frame_button[:index]
      end
  
      if (inputs.mouse.point.inside_rect? rt_canvas.sprite)
        state.last_mouse_down = state.tick_count
        edit_current_animation_frame inputs.mouse.point
      end
    end
  
    def input_keyboard
      # w to save
      if inputs.keyboard.key_down.w
        t = Time.now
        state.save_description = "Time: #{t} (#{t.to_i})"
        gtk.serialize_state 'canvas/state.txt', state
        gtk.serialize_state "tmp/canvas_backups/#{t.to_i}/state.txt", state
        animation_frames.each_with_index do |animation_frame, i|
          queues.update_rt_animation_frame << { index: i,
                                                at: state.tick_count + i,
                                                queue_sprite_creation: true }
          queues.create_sprite << { index: i,
                                    at: state.tick_count + animation_frames.length + i,
                                    path_override: "tmp/canvas_backups/#{t.to_i}/sprite-#{i}.png" }
        end
        gtk.notify! "Canvas saved."
      end
  
      # l to load
      if inputs.keyboard.key_down.l
        args.state = gtk.deserialize_state 'canvas/state.txt'
        animation_frames.each_with_index do |a, i|
          queues.update_rt_animation_frame << { index: i,
                                                at: state.tick_count + i,
                                                queue_sprite_creation: true }
        end
        gtk.notify! "Canvas loaded."
      end
  
      # d to go into delete mode, release to paint
      if inputs.keyboard.key_held.d
        state.edit_mode = :erasing
        gtk.notify! "Erasing." if inputs.keyboard.key_held.d == (state.tick_count - 1)
      elsif inputs.keyboard.key_up.d
        state.edit_mode = :drawing
        gtk.notify! "Drawing."
      end
  
      # a to add a frame to the end
      if inputs.keyboard.key_down.a
        queues.create_sprite << { index: state.animation_frames_selected_index,
                                  at: state.tick_count }
        queues.create_sprite << { index: state.animation_frames_selected_index + 1,
                                  at: state.tick_count }
        add_animation_frame_to_end
        gtk.notify! "Frame added to end."
      end
  
      # c or t to copy
      if (inputs.keyboard.key_down.c || inputs.keyboard.key_down.t)
        state.clipboard = [selected_animation_frame[:pixels]].flatten
        gtk.notify! "Current frame copied."
      end
  
      # v or q to paste
      if (inputs.keyboard.key_down.v || inputs.keyboard.key_down.q) && state.clipboard
        selected_animation_frame[:pixels] = [state.clipboard].flatten
        queues.update_rt_animation_frame << { index: state.animation_frames_selected_index,
                                              at: state.tick_count,
                                              queue_sprite_creation: true }
        gtk.notify! "Pasted."
      end
  
      # f to go forward/next frame
      if (inputs.keyboard.key_down.f)
        if (state.animation_frames_selected_index == (state.animation_frames.length - 1))
          state.animation_frames_selected_index = 0
        else
          state.animation_frames_selected_index += 1
        end
        gtk.notify! "Next frame."
      end
  
      # b to go back/previous frame
      if (inputs.keyboard.key_down.b)
        if (state.animation_frames_selected_index == 0)
          state.animation_frames_selected_index = state.animation_frames.length - 1
        else
          state.animation_frames_selected_index -= 1
        end
        gtk.notify! "Previous frame."
      end
  
      # x to delete frame
      if (inputs.keyboard.key_down.x) && animation_frames.length > 1
        state.clipboard = selected_animation_frame[:pixels]
        state.animation_frames = animation_frames.find_all { |v| v[:index] != state.animation_frames_selected_index }
        if state.animation_frames_selected_index >= state.animation_frames.length
          state.animation_frames_selected_index = state.animation_frames.length - 1
        end
        gtk.notify! "Frame deleted."
      end
    end
  
    def calc_auto_export
      return if user_is_editing?
      return if state.last_mouse_up.elapsed_time != 30
      # auto export current animation frame if there is no editing for 30 ticks
      queues.create_sprite << { index: state.animation_frames_selected_index,
                                at: state.tick_count }
    end
  
    def calc_buttons_frame_selection
      state.buttons_frame_selection.items = animation_frames.length.map_with_index do |i|
        { x: state.buttons_frame_selection.left + i * state.buttons_frame_selection.size,
          y: state.buttons_frame_selection.top - state.buttons_frame_selection.size,
          inner_rect: {
            x: (state.buttons_frame_selection.left + 2) + i * state.buttons_frame_selection.size,
            y: (state.buttons_frame_selection.top - state.buttons_frame_selection.size + 2),
            w: 16,
            h: 16,
          },
          w: state.buttons_frame_selection.size,
          h: state.buttons_frame_selection.size,
          index: i }
      end
    end
  
    def calc_animation_frames
      animation_frames.each_with_index do |animation_frame, i|
        animation_frame[:index] = i
        animation_frame[:rt_name] = "animation_frame_#{i}"
      end
    end
  
    def process_queue_create_sprite
      sprites_to_create = queues.create_sprite
                                .find_all { |h| h[:at].elapsed? }
  
      queues.create_sprite = queues.create_sprite - sprites_to_create
  
      sprites_to_create.each do |h|
        export_animation_frame h[:index], h[:path_override]
      end
    end
  
    def process_queue_reset_sprite
      sprites_to_reset = queues.reset_sprite
                               .find_all { |h| h[:at].elapsed? }
  
      queues.reset_sprite -= sprites_to_reset
  
      sprites_to_reset.each { |h| gtk.reset_sprite (sprite_path h[:index]) }
    end
  
    def process_queue_update_rt_animation_frame
      animation_frames_to_update = queues.update_rt_animation_frame
                                         .find_all { |h| h[:at].elapsed? }
  
      queues.update_rt_animation_frame -= animation_frames_to_update
  
      animation_frames_to_update.each do |h|
        update_animation_frame_render_target animation_frames[h[:index]]
  
        if h[:queue_sprite_creation]
          queues.create_sprite << { index: h[:index],
                                    at: state.tick_count + 1 }
        end
      end
    end
  
    def update_animation_frame_render_target animation_frame
      return if !animation_frame
  
      outputs[animation_frame[:rt_name]].width   = state.rt_canvas.size
      outputs[animation_frame[:rt_name]].height  = state.rt_canvas.size
      outputs[animation_frame[:rt_name]].solids << animation_frame[:pixels].map do |f|
        { x: f.x,
          y: f.y,
          w: 1,
          h: 1, r: 255, g: 255, b: 255 }
      end
    end
  
    def animation_frames
      state.animation_frames
    end
  
    def add_animation_frame_to_end
      animation_frames << {
        index: animation_frames.length,
        pixels: [],
        rt_name: "animation_frame_#{animation_frames.length}"
      }
  
      state.animation_frames_selected_index = (animation_frames.length - 1)
      queues.update_rt_animation_frame << { index: state.animation_frames_selected_index,
                                            at: state.tick_count,
                                            queue_sprite_creation: true }
    end
  
    def sprite_path i
      "canvas/sprite-#{i}.png"
    end
  
    def export_animation_frame i, path_override = nil
      return if !state.animation_frames[i]
  
      outputs.screenshots << state.buttons_frame_selection
                                  .items[i][:inner_rect]
                                  .merge(path: path_override || (sprite_path i))
  
      outputs.screenshots << state.buttons_frame_selection
                                  .items[i][:inner_rect]
                                  .merge(path: "tmp/sprite_backups/#{Time.now.to_i}-sprite-#{i}.png")
  
      queues.reset_sprite << { index: i, at: state.tick_count }
    end
  
    def selected_animation_frame
      state.animation_frames[state.animation_frames_selected_index]
    end
  
    def edit_current_animation_frame point
      draw_area_point = (to_draw_area point)
      if state.edit_mode == :drawing && (!selected_animation_frame[:pixels].include? draw_area_point)
        selected_animation_frame[:pixels] << draw_area_point
        queues.update_rt_animation_frame << { index: state.animation_frames_selected_index,
                                              at: state.tick_count,
                                              queue_sprite_creation: !user_is_editing? }
      elsif state.edit_mode == :erasing && (selected_animation_frame[:pixels].include? draw_area_point)
        selected_animation_frame[:pixels] = selected_animation_frame[:pixels].reject { |p| p == draw_area_point }
        queues.update_rt_animation_frame << { index: state.animation_frames_selected_index,
                                              at: state.tick_count,
                                              queue_sprite_creation: !user_is_editing? }
      end
    end
  
    def user_is_editing?
      state.last_mouse_down > state.last_mouse_up
    end
  
    def to_draw_area point
      x, y = point
      x -= rt_canvas.sprite.x
      y -= rt_canvas.sprite.y
      { x: x.idiv(rt_canvas.zoom),
        y: y.idiv(rt_canvas.zoom) }
    end
  
    def rt_canvas
      state.rt_canvas ||= state.new_entity(:rt_canvas)
    end
  
    def queues
      state.queues ||= state.new_entity(:queues)
    end
  end
  
  $game = OneBitLowrezPaint.new
  
  def tick args
    $game.args = args
    $game.tick
  end
  
  # $gtk.reset

#+end_src

*** Dev Tools - Tile Editor Starting Point - main.rb
#+begin_src ruby
  # ./samples/99_genre_dev_tools/tile_editor_starting_point/app/main.rb
  =begin
  
   APIs listing that haven't been encountered in previous sample apps:
  
   - to_s: Returns a string representation of an object.
     For example, if we had
     500.to_s
     the string "500" would be returned.
     Similar to to_i, which returns an integer representation of an object.
  
   - Ceil: Returns an integer number greater than or equal to the original
     with no decimal.
  
   Reminders:
  
   - ARRAY#inside_rect?: Returns true or false depending on if the point is inside a rect.
  
   - args.outputs.labels: An array. The values generate a label.
     The parameters are [X, Y, TEXT, SIZE, ALIGNMENT, RED, GREEN, BLUE, ALPHA, FONT STYLE]
     For more information about labels, go to mygame/documentation/02-labels.md.
  
   - args.outputs.sprites: An array. The values generate a sprite.
     The parameters are [X, Y, WIDTH, HEIGHT, IMAGE PATH]
     For more information about sprites, go to mygame/documentation/05-sprites.md.
  
   - args.outputs.solids: An array. The values generate a solid.
     The parameters are [X, Y, WIDTH, HEIGHT, RED, GREEN, BLUE]
     For more information about solids, go to mygame/documentation/03-solids-and-borders.md.
  
   - args.outputs.lines: An array. The values generate a line.
     The parameters are [X1, Y1, X2, Y2, RED, GREEN, BLUE]
     For more information about lines, go to mygame/documentation/04-lines.md.
  
   - args.state.new_entity: Used when we want to create a new object, like a sprite or button.
     In this sample app, new_entity is used to create a new button that clears the grid.
     (Remember, you can use state to define ANY property and it will be retained across frames.)
  
  =end
  
  # This sample app shows an empty grid that the user can paint in. There are different image tiles that
  # the user can use to fill the grid, and the "Clear" button can be pressed to clear the grid boxes.
  
  class TileEditor
    attr_accessor :inputs, :state, :outputs, :grid, :args
  
    # Runs all the methods necessary for the game to function properly.
    def tick
      defaults
      render
      check_click
      draw_buttons
    end
  
    # Sets default values
    # Initialization only happens in the first frame
    # NOTE: The values of some of these variables may seem confusingly large at first.
    # The gridSize is 1600 but it seems a lot smaller on the screen, for example.
    # But keep in mind that by using the "W", "A", "S", and "D" keys, you can
    # move the grid's view in all four directions for more grid spaces.
    def defaults
      state.tileCords      ||= []
      state.tileQuantity   ||= 6
      state.tileSize       ||= 50
      state.tileSelected   ||= 1
      state.tempX          ||= 50
      state.tempY          ||= 500
      state.speed          ||= 4
      state.centerX        ||= 4000
      state.centerY        ||= 4000
      state.originalCenter ||= [state.centerX, state.centerY]
      state.gridSize       ||= 1600
      state.lineQuantity   ||= 50
      state.increment      ||= state.gridSize / state.lineQuantity
      state.gridX          ||= []
      state.gridY          ||= []
      state.filled_squares ||= []
      state.grid_border    ||= [390, 140, 500, 500]
  
      get_grid unless state.tempX == 0 # calls get_grid in the first frame only
      determineTileCords unless state.tempX == 0 # calls determineTileCords in first frame
      state.tempX = 0 # sets tempX to 0; the two methods aren't called again
    end
  
    # Calculates the placement of lines or separators in the grid
    def get_grid
      curr_x = state.centerX - (state.gridSize / 2) # starts at left of grid
      deltaX = state.gridSize / state.lineQuantity # finds distance to place vertical lines evenly through width of grid
      (state.lineQuantity + 2).times do
        state.gridX << curr_x # adds curr_x to gridX collection
        curr_x += deltaX # increment curr_x by the distance between vertical lines
      end
  
      curr_y = state.centerY - (state.gridSize / 2) # starts at bottom of grid
      deltaY = state.gridSize / state.lineQuantity # finds distance to place horizontal lines evenly through height of grid
      (state.lineQuantity + 2).times do
        state.gridY << curr_y # adds curr_y to gridY collection
        curr_y += deltaY # increments curr_y to distance between horizontal lines
      end
    end
  
    # Determines coordinate positions of patterned tiles (on the left side of the grid)
    def determineTileCords
      state.tempCounter ||= 1 # initializes tempCounter to 1
      state.tileQuantity.times do # there are 6 different kinds of tiles
        state.tileCords += [[state.tempX, state.tempY, state.tempCounter]] # adds tile definition to collection
        state.tempX += 75 # increments tempX to put horizontal space between the patterned tiles
        state.tempCounter += 1 # increments tempCounter
        if state.tempX > 200 # if tempX exceeds 200 pixels
          state.tempX = 50 # a new row of patterned tiles begins
          state.tempY -= 75 # the new row is 75 pixels lower than the previous row
        end
      end
    end
  
    # Outputs objects (grid, tiles, etc) onto the screen
    def render
      outputs.sprites << state.tileCords.map do # outputs tileCords collection using images in sprites folder
        |x, y, order|
        [x, y, state.tileSize, state.tileSize, 'sprites/image' + order.to_s + ".png"]
      end
      outputs.solids << [0, 0, 1280, 720, 255, 255, 255] # outputs white background
      add_grid # outputs grid
      print_title # outputs title and current tile pattern
    end
  
    # Creates a grid by outputting vertical and horizontal grid lines onto the screen.
    # Outputs sprites for the filled_squares collection onto the screen.
    def add_grid
  
      # Outputs the grid's border.
      outputs.borders << state.grid_border
      temp = 0
  
      # Before looking at the code that outputs the vertical and horizontal lines in the
      # grid, take note of the fact that:
      # grid_border[1] refers to the border's bottom line (running horizontally),
      # grid_border[2] refers to the border's top line (running (horizontally),
      # grid_border[0] refers to the border's left line (running vertically),
      # and grid_border[3] refers to the border's right line (running vertically).
  
      #           [2]
      #       ----------
      #       |        |
      # [0]   |        | [3]
      #       |        |
      #       ----------
      #           [1]
  
      # Calculates the positions and outputs the x grid lines in the color gray.
      state.gridX.map do # perform an action on all elements of the gridX collection
        |x|
        temp += 1 # increment temp
  
        # if x's value is greater than (or equal to) the x value of the border's left side
        # and less than (or equal to) the x value of the border's right side
        if x >= state.centerX - (state.grid_border[2] / 2) && x <= state.centerX + (state.grid_border[2] / 2)
          delta = state.centerX - 640
          # vertical lines have the same starting and ending x positions
          # starting y and ending y positions lead from the bottom of the border to the top of the border
          outputs.lines << [x - delta, state.grid_border[1], x - delta, state.grid_border[1] + state.grid_border[2], 150, 150, 150] # sets definition of vertical line and outputs it
        end
      end
      temp = 0
  
      # Calculates the positions and outputs the y grid lines in the color gray.
      state.gridY.map do # perform an action on all elements of the gridY collection
        |y|
        temp += 1 # increment temp
  
        # if y's value is greater than (or equal to) the y value of the border's bottom side
        # and less than (or equal to) the y value of the border's top side
        if y >= state.centerY - (state.grid_border[3] / 2) && y <= state.centerY + (state.grid_border[3] / 2)
          delta = state.centerY - 393
          # horizontal lines have the same starting and ending y positions
          # starting x and ending x positions lead from the left side of the border to the right side of the border
          outputs.lines << [state.grid_border[0], y - delta, state.grid_border[0] + state.grid_border[3], y - delta, 150, 150, 150] # sets definition of horizontal line and outputs it
        end
      end
  
      # Sets values and outputs sprites for the filled_squares collection.
      state.filled_squares.map do # perform an action on every element of the filled_squares collection
        |x, y, w, h, sprite|
          # if x's value is greater than (or equal to) the x value of 17 pixels to the left of the border's left side
          # and less than (or equal to) the x value of the border's right side
          # and y's value is greater than (or equal to) the y value of the border's bottom side
          # and less than (or equal to) the y value of 25 pixels above the border's top side
          # NOTE: The allowance of 17 pixels and 25 pixels is due to the fact that a grid box may be slightly cut off or
          # not entirely visible in the grid's view (until it is moved using "W", "A", "S", "D")
          if x >= state.centerX - (state.grid_border[2] / 2) - 17 && x <= state.centerX + (state.grid_border[2] / 2) &&
             y >= state.centerY - (state.grid_border[3] / 2) && y <= state.centerY + (state.grid_border[3] / 2) + 25
            # calculations done to place sprites in grid spaces that are meant to filled in
            # mess around with the x and y values and see how the sprite placement changes
            outputs.sprites << [x - state.centerX + 630, y - state.centerY + 360, w, h, sprite]
          end
        end
  
        # outputs a white solid along the left side of the grid (change the color and you'll be able to see it against the white background)
        # state.increment subtracted in x parameter because solid's position is denoted by bottom left corner
        # state.increment subtracted in y parameter to avoid covering the title label
        outputs.primitives << [state.grid_border[0] - state.increment,
                               state.grid_border[1] - state.increment, state.increment, state.grid_border[3] + (state.increment * 2),
                               255, 255, 255].solid
  
        # outputs a white solid along the right side of the grid
        # state.increment subtracted from y parameter to avoid covering title label
        outputs.primitives << [state.grid_border[0] + state.grid_border[2],
                               state.grid_border[1] - state.increment, state.increment, state.grid_border[3] + (state.increment * 2),
                               255, 255, 255].solid
  
        # outputs a white solid along the bottom of the grid
        # state.increment subtracted from y parameter to avoid covering last row of grid boxes
        outputs.primitives << [state.grid_border[0] - state.increment, state.grid_border[1] - state.increment,
                               state.grid_border[2] + (2 * state.increment), state.increment, 255, 255, 255].solid
  
        # outputs a white solid along the top of the grid
        outputs.primitives << [state.grid_border[0] - state.increment, state.grid_border[1] + state.grid_border[3],
                               state.grid_border[2] + (2 * state.increment), state.increment, 255, 255, 255].solid
  
    end
  
    # Outputs title and current tile pattern
    def print_title
      outputs.labels << [640, 700, 'Mouse to Place Tile, WASD to Move Around', 7, 1] # title label
      outputs.lines << horizontal_separator(660, 0, 1280) # outputs horizontal separator
      outputs.labels << [1050, 500, 'Current:', 3, 1] # outputs Current label
      outputs.sprites << [1110, 474, state.tileSize / 2, state.tileSize / 2, 'sprites/image' + state.tileSelected.to_s + ".png"] # outputs sprite of current tile pattern using images in sprites folder; output is half the size of a tile
    end
  
    # Sets the starting position, ending position, and color for the horizontal separator.
    def horizontal_separator y, x, x2
      [x, y, x2, y, 150, 150, 150] # definition of separator; horizontal line means same starting/ending y
    end
  
    # Checks if the mouse is being clicked or dragged
    def check_click
      if inputs.keyboard.key_down.r # if the "r" key is pressed down
        $dragon.reset
      end
  
      if inputs.mouse.down #is mouse up or down?
        state.mouse_held = true
        if inputs.mouse.position.x < state.grid_border[0] # if mouse's x position is inside the grid's borders
          state.tileCords.map do # perform action on all elements of tileCords collection
            |x, y, order|
            # if mouse's x position is greater than (or equal to) the starting x position of a tile
            # and the mouse's x position is also less than (or equal to) the ending x position of that tile,
            # and the mouse's y position is greater than (or equal to) the starting y position of that tile,
            # and the mouse's y position is also less than (or equal to) the ending y position of that tile,
            # (BASICALLY, IF THE MOUSE'S POSITION IS WITHIN THE STARTING AND ENDING POSITIONS OF A TILE)
            if inputs.mouse.position.x >= x && inputs.mouse.position.x <= x + state.tileSize &&
               inputs.mouse.position.y >= y && inputs.mouse.position.y <= y + state.tileSize
              state.tileSelected = order # that tile is selected
            end
          end
        end
      elsif inputs.mouse.up # otherwise, if the mouse is in the "up" state
        state.mouse_held = false # mouse is not held down or dragged
        state.mouse_dragging = false
      end
  
      if state.mouse_held &&    # mouse needs to be down
         !inputs.mouse.click &&     # must not be first click
         ((inputs.mouse.previous_click.point.x - inputs.mouse.position.x).abs > 15 ||
          (inputs.mouse.previous_click.point.y - inputs.mouse.position.y).abs > 15) # Need to move 15 pixels before "drag"
        state.mouse_dragging = true
      end
  
      # if mouse is clicked inside grid's border, search_lines method is called with click input type
      if ((inputs.mouse.click) && (inputs.mouse.click.point.inside_rect? state.grid_border))
        search_lines(inputs.mouse.click.point, :click)
  
      # if mouse is dragged inside grid's border, search_lines method is called with drag input type
      elsif ((state.mouse_dragging) && (inputs.mouse.position.inside_rect? state.grid_border))
        search_lines(inputs.mouse.position, :drag)
      end
  
      # Changes grid's position on screen by moving it up, down, left, or right.
  
      # centerX is incremented by speed if the "d" key is pressed and if that sum is less than
      # the original left side of the center plus half the grid, minus half the top border of grid.
      # MOVES GRID RIGHT (increasing x)
      state.centerX += state.speed if inputs.keyboard.key_held.d &&
                                      (state.centerX + state.speed) < state.originalCenter[0] + (state.gridSize / 2) - (state.grid_border[2] / 2)
      # centerX is decremented by speed if the "a" key is pressed and if that difference is greater than
      # the original left side of the center minus half the grid, plus half the top border of grid.
      # MOVES GRID LEFT (decreasing x)
      state.centerX -= state.speed if inputs.keyboard.key_held.a &&
                                      (state.centerX - state.speed) > state.originalCenter[0] - (state.gridSize / 2) + (state.grid_border[2] / 2)
      # centerY is incremented by speed if the "w" key is pressed and if that sum is less than
      # the original bottom of the center plus half the grid, minus half the right border of grid.
      # MOVES GRID UP (increasing y)
      state.centerY += state.speed if inputs.keyboard.key_held.w &&
                                      (state.centerY + state.speed) < state.originalCenter[1] + (state.gridSize / 2) - (state.grid_border[3] / 2)
      # centerY is decremented by speed if the "s" key is pressed and if the difference is greater than
      # the original bottom of the center minus half the grid, plus half the right border of grid.
      # MOVES GRID DOWN (decreasing y)
      state.centerY -= state.speed if inputs.keyboard.key_held.s &&
                                      (state.centerY - state.speed) > state.originalCenter[1] - (state.gridSize / 2) + (state.grid_border[3] / 2)
    end
  
    # Performs calculations on the gridX and gridY collections, and sets values.
    # Sets the definition of a grid box, including the image that it is filled with.
    def search_lines (point, input_type)
      point.x += state.centerX - 630 # increments x and y
      point.y += state.centerY - 360
      findX = 0
      findY = 0
      increment = state.gridSize / state.lineQuantity # divides grid by number of separators
  
      state.gridX.map do # perform an action on every element of collection
        |x|
        # findX increments x by 10 if point.x is less than that sum and findX is currently 0
        findX = x + 10 if point.x < (x + 10) && findX == 0
      end
  
      state.gridY.map do
        |y|
        # findY is set to y if point.y is less than that value and findY is currently 0
        findY = y if point.y < (y) && findY == 0
      end
      # position of a box is denoted by bottom left corner, which is why the increment is being subtracted
      grid_box = [findX - (increment.ceil), findY - (increment.ceil), increment.ceil, increment.ceil,
                  "sprites/image" + state.tileSelected.to_s + ".png"] # sets sprite definition
  
      if input_type == :click # if user clicks their mouse
        if state.filled_squares.include? grid_box # if grid box is already filled in
          state.filled_squares.delete grid_box # box is cleared and removed from filled_squares
        else
          state.filled_squares << grid_box # otherwise, box is filled in and added to filled_squares
        end
      elsif input_type == :drag # if user drags mouse
        unless state.filled_squares.include? grid_box # unless grid box dragged over is already filled in
          state.filled_squares << grid_box # box is filled in and added to filled_squares
        end
      end
    end
  
    # Creates a "Clear" button using labels and borders.
    def draw_buttons
      x, y, w, h = 390, 50, 240, 50
      state.clear_button        ||= state.new_entity(:button_with_fade)
  
      # x and y positions are set to display "Clear" label in center of the button
      # Try changing first two parameters to simply x, y and see what happens to the text placement
      state.clear_button.label  ||= [x + w.half, y + h.half + 10, "Clear", 0, 1]
      state.clear_button.border ||= [x, y, w, h] # definition of button's border
  
      # If the mouse is clicked inside the borders of the clear button
      if inputs.mouse.click && inputs.mouse.click.point.inside_rect?(state.clear_button.border)
        state.clear_button.clicked_at = inputs.mouse.click.created_at # value is frame of mouse click
        state.filled_squares.clear # filled squares collection is emptied (squares are cleared)
        inputs.mouse.previous_click = nil # no previous click
      end
  
      outputs.labels << state.clear_button.label # outputs clear button
      outputs.borders << state.clear_button.border
  
      # When the clear button is clicked, the color of the button changes
      # and the transparency changes, as well. If you change the time from
      # 0.25.seconds to 1.25.seconds or more, the change will last longer.
      if state.clear_button.clicked_at
        outputs.solids << [x, y, w, h, 0, 180, 80, 255 * state.clear_button.clicked_at.ease(0.25.seconds, :flip)]
      end
    end
  end
  
  $tile_editor = TileEditor.new
  
  def tick args
    $tile_editor.inputs = args.inputs
    $tile_editor.grid = args.grid
    $tile_editor.args = args
    $tile_editor.outputs = args.outputs
    $tile_editor.state = args.state
    $tile_editor.tick
    tick_instructions args, "Roll your own tile editor. CLICK to select a sprite. CLICK in grid to place sprite. WASD to move around."
  end
  
  def tick_instructions args, text, y = 715
    return if args.state.key_event_occurred
    if args.inputs.mouse.click ||
       args.inputs.keyboard.directional_vector ||
       args.inputs.keyboard.key_down.enter ||
       args.inputs.keyboard.key_down.escape
      args.state.key_event_occurred = true
    end
  
    args.outputs.debug << [0, y - 50, 1280, 60].solid
    args.outputs.debug << [640, y, text, 1, 1, 255, 255, 255].label
    args.outputs.debug << [640, y - 25, "(click to dismiss instructions)" , -2, 1, 255, 255, 255].label
  end

#+end_src

*** Dungeon Crawl - Classics Jam - main.rb
#+begin_src ruby
  # ./samples/99_genre_dungeon_crawl/classics_jam/app/main.rb
  class Game
    attr_gtk
  
    def tick
      defaults
      render
      input
      calc
    end
  
    def defaults
      player.x              ||= 640
      player.y              ||= 360
      player.w              ||= 16
      player.h              ||= 16
      player.attacked_at    ||= -1
      player.angle          ||= 0
      player.future_player  ||= future_player_position 0, 0
      player.projectiles    ||= []
      player.damage         ||= 0
      state.level           ||= create_level level_one_template
    end
  
    def render
      outputs.sprites << level.walls.map do |w|
        w.merge(path: 'sprites/square/gray.png')
      end
  
      outputs.sprites << level.spawn_locations.map do |s|
        s.merge(path: 'sprites/square/blue.png')
      end
  
      outputs.sprites << player.projectiles.map do |p|
        p.merge(path: 'sprites/square/blue.png')
      end
  
      outputs.sprites << level.enemies.map do |e|
        e.merge(path: 'sprites/square/red.png')
      end
  
      outputs.sprites << player.merge(path: 'sprites/circle/green.png', angle: player.angle)
  
      outputs.labels << { x: 30, y: 30.from_top, text: "damage: #{player.damage || 0}" }
    end
  
    def input
      player.angle = inputs.directional_angle || player.angle
      if inputs.controller_one.key_down.a || inputs.keyboard.key_down.space
        player.attacked_at = state.tick_count
      end
    end
  
    def calc
      calc_player
      calc_projectiles
      calc_enemies
      calc_spawn_locations
    end
  
    def calc_player
      if player.attacked_at == state.tick_count
        player.projectiles << { at: state.tick_count,
                                x: player.x,
                                y: player.y,
                                angle: player.angle,
                                w: 4,
                                h: 4 }.center_inside_rect(player)
      end
  
      if player.attacked_at.elapsed_time > 5
        future_player = future_player_position inputs.left_right * 2, inputs.up_down * 2
        future_player_collision = future_collision player, future_player, level.walls
        player.x = future_player_collision.x if !future_player_collision.dx_collision
        player.y = future_player_collision.y if !future_player_collision.dy_collision
      end
    end
  
    def calc_projectile_collisions entities
      entities.each do |e|
        e.damage ||= 0
        player.projectiles.each do |p|
          if !p.collided && (p.intersect_rect? e)
            p.collided = true
            e.damage  += 1
          end
        end
      end
    end
  
    def calc_projectiles
      player.projectiles.map! do |p|
        dx, dy = p.angle.vector 10
        p.merge(x: p.x + dx, y: p.y + dy)
      end
  
      calc_projectile_collisions level.walls + level.enemies + level.spawn_locations
      player.projectiles.reject! { |p| p.at.elapsed_time > 10000 }
      player.projectiles.reject! { |p| p.collided }
      level.enemies.reject! { |e| e.damage > e.hp }
      level.spawn_locations.reject! { |s| s.damage > s.hp }
    end
  
    def calc_enemies
      level.enemies.map! do |e|
        dx =  0
        dx =  1 if e.x < player.x
        dx = -1 if e.x > player.x
        dy =  0
        dy =  1 if e.y < player.y
        dy = -1 if e.y > player.y
        future_e           = future_entity_position dx, dy, e
        future_e_collision = future_collision e, future_e, level.enemies + level.walls
        e.next_x = e.x
        e.next_y = e.y
        e.next_x = future_e_collision.x if !future_e_collision.dx_collision
        e.next_y = future_e_collision.y if !future_e_collision.dy_collision
        e
      end
  
      level.enemies.map! do |e|
        e.x = e.next_x
        e.y = e.next_y
        e
      end
  
      level.enemies.each do |e|
        player.damage += 1 if e.intersect_rect? player
      end
    end
  
    def calc_spawn_locations
      level.spawn_locations.map! do |s|
        s.merge(countdown: s.countdown - 1)
      end
      level.spawn_locations
           .find_all { |s| s.countdown.neg? }
           .each do |s|
        s.countdown = s.rate
        s.merge(countdown: s.rate)
        new_enemy = create_enemy s
        if !(level.enemies.find { |e| e.intersect_rect? new_enemy })
          level.enemies << new_enemy
        end
      end
    end
  
    def create_enemy spawn_location
      to_cell(spawn_location.ordinal_x, spawn_location.ordinal_y).merge hp: 2
    end
  
    def create_level level_template
      {
        walls:           level_template.walls.map { |w| to_cell(w.ordinal_x, w.ordinal_y).merge(w) },
        enemies:         [],
        spawn_locations: level_template.spawn_locations.map { |s| to_cell(s.ordinal_x, s.ordinal_y).merge(s) }
      }
    end
  
    def level_one_template
      {
        walls:           [{ ordinal_x: 25, ordinal_y: 20},
                          { ordinal_x: 25, ordinal_y: 21},
                          { ordinal_x: 25, ordinal_y: 22},
                          { ordinal_x: 25, ordinal_y: 23}],
        spawn_locations: [{ ordinal_x: 10, ordinal_y: 10, rate: 120, countdown: 0, hp: 5 }]
      }
    end
  
    def player
      state.player ||= {}
    end
  
    def level
      state.level  ||= {}
    end
  
    def future_collision entity, future_entity, others
      dx_collision = others.find { |o| o != entity && (o.intersect_rect? future_entity.dx) }
      dy_collision = others.find { |o| o != entity && (o.intersect_rect? future_entity.dy) }
  
      {
        dx_collision: dx_collision,
        x: future_entity.dx.x,
        dy_collision: dy_collision,
        y: future_entity.dy.y
      }
    end
  
    def future_entity_position dx, dy, entity
      {
        dx:   entity.merge(x: entity.x + dx),
        dy:   entity.merge(y: entity.y + dy),
        both: entity.merge(x: entity.x + dx, y: entity.y + dy)
      }
    end
  
    def future_player_position  dx, dy
      future_entity_position dx, dy, player
    end
  
    def to_cell ordinal_x, ordinal_y
      { x: ordinal_x * 16, y: ordinal_y * 16, w: 16, h: 16 }
    end
  end
  
  def tick args
    $game ||= Game.new
    $game.args = args
    $game.tick
  end
  
  $gtk.reset
  $game = nil

#+end_src

*** Fighting - Special Move Inputs - main.rb
#+begin_src ruby
  # ./samples/99_genre_fighting/01_special_move_inputs/app/main.rb
  def tick args
    #tick_instructions args, "Use LEFT and RIGHT arrow keys to move and SPACE to jump."
    defaults args
    render args
    input args
    calc args
  end
  
  # sets default values and creates empty collections
  # initialization only happens in the first frame
  def defaults args
    fiddle args
  
    args.state.tick_count = args.state.tick_count
    args.state.bridge_top = 128
    args.state.player.x  ||= 0                        # initializes player's properties
    args.state.player.y  ||= args.state.bridge_top
    args.state.player.w  ||= 64
    args.state.player.h  ||= 64
    args.state.player.dy ||= 0
    args.state.player.dx ||= 0
    args.state.player.r  ||= 0
    args.state.game_over_at ||= 0
    args.state.animation_time ||=0
  
    args.state.timeleft ||=0
    args.state.timeright ||=0
    args.state.lastpush ||=0
  
    args.state.inputlist ||=  ["j","k","l"]
  end
  
  # sets enemy, player, hammer values
  def fiddle args
    args.state.gravity                     = -0.5
    args.state.player_jump_power           = 10      # sets player values
    args.state.player_jump_power_duration  = 5
    args.state.player_max_run_speed        = 20
    args.state.player_speed_slowdown_rate  = 0.9
    args.state.player_acceleration         = 0.9
  end
  
  # outputs objects onto the screen
  def render args
    if (args.state.player.dx < 0.01) && (args.state.player.dx > -0.01)
      args.state.player.dx = 0
    end
  
    #move list
    (args.layout.rect_group row: 0, col_from_right: 8, drow: 0.3,
                            merge: { vertical_alignment_enum: 0, size_enum: -2 },
                            group: [
                              { text: "move:             WASD" },
                              { text: "jump:             Space" },
                              { text: "attack forwards:  J (while on ground" },
                              { text: "attack upwards:   K (while on groud)" },
                              { text: "attack backwards: J (while on ground and holding A)" },
                              { text: "attack downwards: K (while in air)" },
                              { text: "dash attack:      J, K in quick succession." },
                              { text: "shield: hold      J, K at the same time." },
                              { text: "dash backwards:   A, A in quick succession." },
                            ]).into args.outputs.labels
  
    # registered moves
    args.outputs.labels << { x: 0.to_layout_col,
                             y: 0.to_layout_row,
                             text: "input history",
                             size_enum: -2,
                             vertical_alignment_enum: 0 }
  
    (args.state.inputlist.take(5)).map do |s|
      { text: s, size_enum: -2, vertical_alignment_enum: 0 }
    end.yield_self do |group|
      (args.layout.rect_group row: 0.3, col: 0, drow: 0.3, group: group).into args.outputs.labels
    end
  
  
    #sprites
    player = [args.state.player.x, args.state.player.y,
              args.state.player.w, args.state.player.h,
              "sprites/square/white.png",
              args.state.player.r]
  
    playershield = [args.state.player.x - 20, args.state.player.y - 10,
                    args.state.player.w + 20, args.state.player.h + 20,
                    "sprites/square/blue.png",
                    args.state.player.r,
                    0]
  
    playerjab = [args.state.player.x + 32, args.state.player.y,
                 args.state.player.w, args.state.player.h,
                 "sprites/isometric/indigo.png",
                 args.state.player.r,
                 0]
  
    playerupper = [args.state.player.x, args.state.player.y + 32,
                   args.state.player.w, args.state.player.h,
                   "sprites/isometric/indigo.png",
                   args.state.player.r+90,
                   0]
  
    if ((args.state.tick_count - args.state.lastpush) <= 15)
      if (args.state.inputlist[0] == "<<")
        player = [args.state.player.x, args.state.player.y,
                  args.state.player.w, args.state.player.h,
                  "sprites/square/yellow.png", args.state.player.r]
      end
  
      if (args.state.inputlist[0] == "shield")
        player = [args.state.player.x, args.state.player.y,
                  args.state.player.w, args.state.player.h,
                  "sprites/square/indigo.png", args.state.player.r]
  
        playershield = [args.state.player.x - 10, args.state.player.y - 10,
                        args.state.player.w + 20, args.state.player.h + 20,
                        "sprites/square/blue.png", args.state.player.r, 50]
      end
  
      if (args.state.inputlist[0] == "back-attack")
        playerjab = [args.state.player.x - 20, args.state.player.y,
                     args.state.player.w - 10, args.state.player.h,
                     "sprites/isometric/indigo.png", args.state.player.r, 255]
      end
  
      if (args.state.inputlist[0] == "forward-attack")
        playerjab = [args.state.player.x + 32, args.state.player.y,
                     args.state.player.w, args.state.player.h,
                     "sprites/isometric/indigo.png", args.state.player.r, 255]
      end
  
      if (args.state.inputlist[0] == "up-attack")
        playerupper = [args.state.player.x, args.state.player.y + 32,
                       args.state.player.w, args.state.player.h,
                       "sprites/isometric/indigo.png", args.state.player.r + 90, 255]
      end
  
      if (args.state.inputlist[0] == "dair")
        playerupper = [args.state.player.x, args.state.player.y - 32,
                       args.state.player.w, args.state.player.h,
                       "sprites/isometric/indigo.png", args.state.player.r + 90, 255]
      end
  
      if (args.state.inputlist[0] == "dash-attack")
        playerupper = [args.state.player.x, args.state.player.y + 32,
                       args.state.player.w, args.state.player.h,
                       "sprites/isometric/violet.png", args.state.player.r + 90, 255]
  
        playerjab = [args.state.player.x + 32, args.state.player.y,
                     args.state.player.w, args.state.player.h,
                     "sprites/isometric/violet.png", args.state.player.r, 255]
      end
    end
  
    args.outputs.sprites << playerjab
    args.outputs.sprites << playerupper
    args.outputs.sprites << player
    args.outputs.sprites << playershield
  
    args.outputs.solids << 20.map_with_index do |i| # uses 20 squares to form bridge
      [i * 64, args.state.bridge_top - 64, 64, 64]
    end
  end
  
  # Performs calculations to move objects on the screen
  def calc args
    # Since velocity is the change in position, the change in x increases by dx. Same with y and dy.
    args.state.player.x  += args.state.player.dx
    args.state.player.y  += args.state.player.dy
  
    # Since acceleration is the change in velocity, the change in y (dy) increases every frame
    args.state.player.dy += args.state.gravity
  
    # player's y position is either current y position or y position of top of
    # bridge, whichever has a greater value
    # ensures that the player never goes below the bridge
    args.state.player.y  = args.state.player.y.greater(args.state.bridge_top)
  
    # player's x position is either the current x position or 0, whichever has a greater value
    # ensures that the player doesn't go too far left (out of the screen's scope)
    args.state.player.x  = args.state.player.x.greater(0)
  
    # player is not falling if it is located on the top of the bridge
    args.state.player.falling = false if args.state.player.y == args.state.bridge_top
    #args.state.player.rect = [args.state.player.x, args.state.player.y, args.state.player.h, args.state.player.w] # sets definition for player
  end
  
  # Resets the player by changing its properties back to the values they had at initialization
  def reset_player args
    args.state.player.x = 0
    args.state.player.y = args.state.bridge_top
    args.state.player.dy = 0
    args.state.player.dx = 0
    args.state.enemy.hammers.clear # empties hammer collection
    args.state.enemy.hammer_queue.clear # empties hammer_queue
    args.state.game_over_at = args.state.tick_count # game_over_at set to current frame (or passage of time)
  end
  
  # Processes input from the user to move the player
  def input args
    if args.state.inputlist.length > 5
      args.state.inputlist.pop
    end
  
    should_process_special_move = (args.inputs.keyboard.key_down.j)           ||
                                  (args.inputs.keyboard.key_down.k)           ||
                                  (args.inputs.keyboard.key_down.a)           ||
                                  (args.inputs.keyboard.key_down.d)           ||
                                  (args.inputs.controller_one.key_down.y)     ||
                                  (args.inputs.controller_one.key_down.x)     ||
                                  (args.inputs.controller_one.key_down.left)  ||
                                  (args.inputs.controller_one.key_down.right)
  
    if (should_process_special_move)
      if (args.inputs.keyboard.key_down.j && args.inputs.keyboard.key_down.k) ||
         (args.inputs.controller_one.key_down.x && args.inputs.controller_one.key_down.y)
        args.state.inputlist.unshift("shield")
      elsif (args.inputs.keyboard.key_down.k || args.inputs.controller_one.key_down.y) &&
            (args.state.inputlist[0] == "forward-attack") && ((args.state.tick_count - args.state.lastpush) <= 15)
        args.state.inputlist.unshift("dash-attack")
        args.state.player.dx = 20
      elsif (args.inputs.keyboard.key_down.j && args.inputs.keyboard.a) ||
            (args.inputs.controller_one.key_down.x && args.inputs.controller_one.key_down.left)
        args.state.inputlist.unshift("back-attack")
      elsif ( args.inputs.controller_one.key_down.x || args.inputs.keyboard.key_down.j)
        args.state.inputlist.unshift("forward-attack")
      elsif (args.inputs.keyboard.key_down.k || args.inputs.controller_one.key_down.y) &&
            (args.state.player.y > 128)
        args.state.inputlist.unshift("dair")
      elsif (args.inputs.keyboard.key_down.k || args.inputs.controller_one.key_down.y)
        args.state.inputlist.unshift("up-attack")
      elsif (args.inputs.controller_one.key_down.left || args.inputs.keyboard.key_down.a) &&
            (args.state.inputlist[0] == "<") &&
            ((args.state.tick_count - args.state.lastpush) <= 10)
        args.state.inputlist.unshift("<<")
        args.state.player.dx = -15
      elsif (args.inputs.controller_one.key_down.left || args.inputs.keyboard.key_down.a)
        args.state.inputlist.unshift("<")
        args.state.timeleft = args.state.tick_count
      elsif (args.inputs.controller_one.key_down.right || args.inputs.keyboard.key_down.d)
        args.state.inputlist.unshift(">")
      end
  
      args.state.lastpush = args.state.tick_count
    end
  
    if args.inputs.keyboard.space || args.inputs.controller_one.r2   # if the user presses the space bar
      args.state.player.jumped_at ||= args.state.tick_count # jumped_at is set to current frame
  
      # if the time that has passed since the jump is less than the player's jump duration and
      # the player is not falling
      if args.state.player.jumped_at.elapsed_time < args.state.player_jump_power_duration && !args.state.player.falling
        args.state.player.dy = args.state.player_jump_power # change in y is set to power of player's jump
      end
    end
  
    # if the space bar is in the "up" state (or not being pressed down)
    if args.inputs.keyboard.key_up.space || args.inputs.controller_one.key_up.r2
      args.state.player.jumped_at = nil # jumped_at is empty
      args.state.player.falling = true # the player is falling
    end
  
    if args.inputs.left # if left key is pressed
      if args.state.player.dx < -5
        args.state.player.dx = args.state.player.dx
      else
        args.state.player.dx = -5
      end
  
    elsif args.inputs.right # if right key is pressed
      if args.state.player.dx > 5
        args.state.player.dx = args.state.player.dx
      else
        args.state.player.dx = 5
      end
    else
      args.state.player.dx *= args.state.player_speed_slowdown_rate # dx is scaled down
    end
  
    if ((args.state.player.dx).abs > 5) #&& ((args.state.tick_count - args.state.lastpush) <= 10)
      args.state.player.dx *= 0.95
    end
  end
  
  def tick_instructions args, text, y = 715
    return if args.state.key_event_occurred
    if args.inputs.mouse.click ||
       args.inputs.keyboard.directional_vector ||
       args.inputs.keyboard.key_down.enter ||
       args.inputs.keyboard.key_down.space ||
       args.inputs.keyboard.key_down.escape
      args.state.key_event_occurred = true
    end
  
    args.outputs.debug << [0, y - 50, 1280, 60].solid
    args.outputs.debug << [640, y, text, 1, 1, 255, 255, 255].label
    args.outputs.debug << [640, y - 25, "(click to dismiss instructions)" , -2, 1, 255, 255, 255].label
  end

#+end_src

*** Lowrez - Nokia 3310 - main.rb
#+begin_src ruby
  # ./samples/99_genre_lowrez/nokia_3310/app/main.rb
  require 'app/nokia.rb'
  
  def tick args
    # =======================================================================
    # ==== HELLO WORLD ======================================================
    # =======================================================================
    # Steps to get started:
    # 1. ~def tick args~ is the entry point for your game.
    # 2. There are quite a few code samples below, remove the "##"
    #    before each line and save the file to see the changes.
    # 3. 0,  0 is in bottom left and 83, 47 is in top right corner.
    # 4. Be sure to come to the discord channel if you need
    #    more help: [[http://discord.dragonruby.org]].
  
    # Commenting and uncommenting code:
    # - Add a "#" infront of lines to comment out code
    # - Remove the "#" infront of lines to comment out code
  
    # Invoke the hello_world subroutine/method
    hello_world args # <---- add a "#" to the beginning of the line to stop running this subroutine/method.
  
    # =======================================================================
    # ==== HOW TO RENDER A LABEL ============================================
    # =======================================================================
  
    # Uncomment the line below to invoke the how_to_render_a_label subroutine/method.
    # Note: The method is defined in this file with the signature ~def how_to_render_a_label args~
    #       Scroll down to the method to see the details.
  
    # Remove the "#" at the beginning of the line below
    # how_to_render_a_label args # <---- remove the "#" at the beginning of this line to run the method
  
  
    # =======================================================================
    # ==== HOW TO RENDER A FILLED SQUARE (SOLID) ============================
    # =======================================================================
    # Remove the "#" at the beginning of the line below
    # how_to_render_solids args
  
  
    # =======================================================================
    # ==== HOW TO RENDER AN UNFILLED SQUARE (BORDER) ========================
    # =======================================================================
    # Remove the "#" at the beginning of the line below
    # how_to_render_borders args
  
  
    # =======================================================================
    # ==== HOW TO RENDER A LINE =============================================
    # =======================================================================
    # Remove the "#" at the beginning of the line below
    # how_to_render_lines args
  
  
    # =======================================================================
    # == HOW TO RENDER A SPRITE =============================================
    # =======================================================================
    # Remove the "#" at the beginning of the line below
    # how_to_render_sprites args
  
  
    # =======================================================================
    # ==== HOW TO MOVE A SPRITE BASED OFF OF USER INPUT =====================
    # =======================================================================
    # Remove the "#" at the beginning of the line below
    # how_to_move_a_sprite args
  
  
    # =======================================================================
    # ==== HOW TO ANIMATE A SPRITE (SEPERATE PNGS) ==========================
    # =======================================================================
    # Remove the "#" at the beginning of the line below
    # how_to_animate_a_sprite args
  
  
    # =======================================================================
    # ==== HOW TO ANIMATE A SPRITE (SPRITE SHEET) ===========================
    # =======================================================================
    # Remove the "#" at the beginning of the line below
    # how_to_animate_a_sprite_sheet args
  
  
    # =======================================================================
    # ==== HOW TO DETERMINE COLLISION =============================================
    # =======================================================================
    # Remove the "#" at the beginning of the line below
    # how_to_determine_collision args
  
  
    # =======================================================================
    # ==== HOW TO CREATE BUTTONS ==================================================
    # =======================================================================
    # Remove the "#" at the beginning of the line below
    # how_to_create_buttons args
  
    # ==== The line below renders a debug grid, mouse information, and current tick
    # render_debug args
  end
  
  # =======================================================================
  # ==== HELLO WORLD ======================================================
  # =======================================================================
  def hello_world args
    args.nokia.solids  << { x: 0, y: 64, w: 10, h: 10, r: 255 }
  
    args.nokia.labels  << {
      x: 42,
      y: 46,
      text: "nokia 3310 jam 3",
      size_enum: NOKIA_FONT_SM,
      alignment_enum: 1,
      r: 0,
      g: 0,
      b: 0,
      a: 255,
      font: NOKIA_FONT_PATH
    }
  
    args.nokia.sprites << {
      x: 42 - 10,
      y: 26 - 10,
      w: 20,
      h: 20,
      path: 'sprites/monochrome-ship.png',
      a: 255,
      angle: args.state.tick_count % 360
    }
  end
  
  # =======================================================================
  # ==== HOW TO RENDER A LABEL ============================================
  # =======================================================================
  def how_to_render_a_label args
    # NOTE: Text is aligned from the TOP LEFT corner
  
    # Render an EXTRA LARGE/XL label (remove the "#" in front of each line below)
    args.nokia.labels << { x: 0, y: 46, text: "Hello World",
                           size_enum: NOKIA_FONT_XL,
                           r: 0, g: 0, b: 0, a: 255,
                           font: NOKIA_FONT_PATH }
  
    # Render a LARGE/LG label (remove the "#" in front of each line below)
    args.nokia.labels << { x: 0, y: 29, text: "Hello World",
                            size_enum: NOKIA_FONT_LG,
                            r: 0, g: 0, b: 0, a: 255,
                            font: NOKIA_FONT_PATH }
  
    # Render a MEDIUM/MD label (remove the "#" in front of each line below)
    args.nokia.labels << { x: 0, y: 16, text: "Hello World",
                            size_enum: NOKIA_FONT_MD,
                            r: 0, g: 0, b: 0, a: 255,
                            font: NOKIA_FONT_PATH }
  
    # Render a SMALL/SM label (remove the "#" in front of each line below)
    args.nokia.labels << { x: 0, y: 7, text: "Hello World",
                            size_enum: NOKIA_FONT_SM,
                            r: 0, g: 0, b: 0, a: 255,
                            font: NOKIA_FONT_PATH }
  
    # You are provided args.nokia.default_label which returns a Hash that you
    # can ~merge~ properties with
    # Example 1
    args.nokia.labels << args.nokia
                              .default_label
                              .merge(text: "Default")
  
    # Example 2
    args.nokia.labels << args.nokia
                              .default_label
                              .merge(x: 31,
                                     text: "Default")
  end
  
  # =============================================================================
  # ==== HOW TO RENDER FILLED SQUARES (SOLIDS) ==================================
  # =============================================================================
  def how_to_render_solids args
    # Render a square at 0, 0 with a width and height of 1
    args.nokia.solids << { x: 0, y: 0, w: 1, h: 1 }
  
    # Render a square at 1, 1 with a width and height of 2
    args.nokia.solids << { x: 1, y: 1, w: 2, h: 2 }
  
    # Render a square at 3, 3 with a width and height of 3
    args.nokia.solids << { x: 3, y: 3, w: 3, h: 3 }
  
    # Render a square at 6, 6 with a width and height of 4
    args.nokia.solids << { x: 6, y: 6, w: 4, h: 4 }
  end
  
  # =============================================================================
  # ==== HOW TO RENDER UNFILLED SQUARES (BORDERS) ===============================
  # =============================================================================
  def how_to_render_borders args
    # Render a square at 0, 0 with a width and height of 3
    args.nokia.borders << { x: 0, y: 0, w: 3, h: 3, a: 255 }
  
    # Render a square at 3, 3 with a width and height of 3
    args.nokia.borders << { x: 3, y: 3, w: 4, h: 4, a: 255 }
  
    # Render a square at 5, 5 with a width and height of 4
    args.nokia.borders << { x: 7, y: 7, w: 5, h: 5, a: 255 }
  end
  
  # =============================================================================
  # ==== HOW TO RENDER A LINE ===================================================
  # =============================================================================
  def how_to_render_lines args
    # Render a horizontal line at the bottom
    args.nokia.lines << { x: 0, y: 0, x2: 83, y2:  0 }
  
    # Render a vertical line at the left
    args.nokia.lines << { x: 0, y: 0, x2:  0, y2: 47 }
  
    # Render a diagonal line starting from the bottom left and going to the top right
    args.nokia.lines << { x: 0, y: 0, x2: 83, y2: 47 }
  end
  
  # =============================================================================
  # == HOW TO RENDER A SPRITE ===================================================
  # =============================================================================
  def how_to_render_sprites args
    # Loop 10 times and create 10 sprites in 10 positions
    # Render a sprite at the bottom left with a width and height of 5 and a path of 'sprites/monochrome-ship.png'
    10.times do |i|
      args.nokia.sprites << {
        x: i * 8.4,
        y: i * 4.8,
        w: 5,
        h: 5,
        path: 'sprites/monochrome-ship.png'
      }
    end
  
    # Given an array of positions create sprites
    positions = [
      { x: 20, y: 32 },
      { x: 45, y: 15 },
      { x: 72, y: 23 },
    ]
  
    positions.each do |position|
      # use Ruby's ~Hash#merge~ function to create a sprite
      args.nokia.sprites << position.merge(path: 'sprites/monochrome-ship.png',
                                            w: 5,
                                            h: 5)
    end
  end
  
  # =============================================================================
  # ==== HOW TO ANIMATE A SPRITE (SEPERATE PNGS) ==========================
  # =============================================================================
  def how_to_animate_a_sprite args
    # STEP 1: Define when you want the animation to start. The animation in this case will start in 3 seconds
    start_animation_on_tick = 180
  
    # STEP 2: Get the frame_index given the start tick.
    sprite_index = start_animation_on_tick.frame_index count: 7,     # how many sprites?
                                                       hold_for: 8,  # how long to hold each sprite?
                                                       repeat: true  # should it repeat?
  
    # STEP 3: frame_index will return nil if the frame hasn't arrived yet
    if sprite_index
      # if the sprite_index is populated, use it to determine the sprite path and render it
      sprite_path  = "sprites/explosion-#{sprite_index}.png"
      args.nokia.sprites << { x: 42 - 16,
                               y: 47 - 32,
                               w: 32,
                               h: 32,
                               path: sprite_path }
    else
      # if the sprite_index is nil, render a countdown instead
      countdown_in_seconds = ((start_animation_on_tick - args.state.tick_count) / 60).round(1)
  
      args.nokia.labels  << args.nokia
                                 .default_label
                                 .merge(x: 0,
                                        y: 18,
                                        text: "Count Down: #{countdown_in_seconds.to_sf}",
                                        alignment_enum: 0)
    end
  
    # render the current tick and the resolved sprite index
    args.nokia.labels  << args.nokia
                                 .default_label
                                 .merge(x: 0,
                                        y: 11,
                                        text: "Tick: #{args.state.tick_count}")
    args.nokia.labels  << args.nokia
                                 .default_label
                                 .merge(x: 0,
                                        y: 5,
                                        text: "sprite_index: #{sprite_index}")
  end
  
  # =============================================================================
  # ==== HOW TO ANIMATE A SPRITE (SPRITE SHEET) =================================
  # =============================================================================
  def how_to_animate_a_sprite_sheet args
    # STEP 1: Define when you want the animation to start. The animation in this case will start in 3 seconds
    start_animation_on_tick = 180
  
    # STEP 2: Get the frame_index given the start tick.
    sprite_index = start_animation_on_tick.frame_index count: 7,     # how many sprites?
                                                       hold_for: 8,  # how long to hold each sprite?
                                                       repeat: true  # should it repeat?
  
    # STEP 3: frame_index will return nil if the frame hasn't arrived yet
    if sprite_index
      # if the sprite_index is populated, use it to determine the source rectangle and render it
      args.nokia.sprites << {
        x: 42 - 16,
        y: 47 - 32,
        w: 32,
        h: 32,
        path:  "sprites/explosion-sheet.png",
        source_x: 32 * sprite_index,
        source_y: 0,
        source_w: 32,
        source_h: 32
      }
    else
      # if the sprite_index is nil, render a countdown instead
      countdown_in_seconds = ((start_animation_on_tick - args.state.tick_count) / 60).round(1)
  
      args.nokia.labels  << args.nokia
                                 .default_label
                                 .merge(x: 0,
                                        y: 18,
                                        text: "Count Down: #{countdown_in_seconds.to_sf}",
                                        alignment_enum: 0)
    end
  
    # render the current tick and the resolved sprite index
    args.nokia.labels  << args.nokia
                                 .default_label
                                 .merge(x: 0,
                                        y: 11,
                                        text: "tick: #{args.state.tick_count}")
    args.nokia.labels  << args.nokia
                                 .default_label
                                 .merge(x: 0,
                                        y: 5,
                                        text: "sprite_index: #{sprite_index}")
  end
  
  # =============================================================================
  # ==== HOW TO STORE STATE, ACCEPT INPUT, AND RENDER SPRITE BASED OFF OF STATE =
  # =============================================================================
  def how_to_move_a_sprite args
    args.nokia.labels << args.nokia
                              .default_label
                              .merge(x: 42,
                                     y: 46, text: "Use Arrow Keys",
                                     alignment_enum: 1)
  
    args.nokia.labels << args.nokia
                              .default_label
                              .merge(x: 42,
                                     y: 41, text: "Or WASD",
                                     alignment_enum: 1)
  
    args.nokia.labels << args.nokia
                              .default_label
                              .merge(x: 42,
                                     y: 36, text: "Or Click",
                                     alignment_enum: 1)
  
    # set the initial values for x and y using ||= ("or equal operator")
    args.state.ship.x ||= 0
    args.state.ship.y ||= 0
  
    # if a mouse click occurs, update the ship's x and y to be the location of the click
    if args.nokia.mouse_click
      args.state.ship.x = args.nokia.mouse_click.x
      args.state.ship.y = args.nokia.mouse_click.y
    end
  
    # if a or left arrow is pressed/held, decrement the ships x position
    if args.nokia.keyboard.left
      args.state.ship.x -= 1
    end
  
    # if d or right arrow is pressed/held, increment the ships x position
    if args.nokia.keyboard.right
      args.state.ship.x += 1
    end
  
    # if s or down arrow is pressed/held, decrement the ships y position
    if args.nokia.keyboard.down
      args.state.ship.y -= 1
    end
  
    # if w or up arrow is pressed/held, increment the ships y position
    if args.nokia.keyboard.up
      args.state.ship.y += 1
    end
  
    # render the sprite to the screen using the position stored in args.state.ship
    args.nokia.sprites << {
      x: args.state.ship.x,
      y: args.state.ship.y,
      w: 5,
      h: 5,
      path: 'sprites/monochrome-ship.png',
      # parameters beyond this point are optional
      angle: 0, # Note: rotation angle is denoted in degrees NOT radians
      r: 255,
      g: 255,
      b: 255,
      a: 255
    }
  end
  
  # =======================================================================
  # ==== HOW TO DETERMINE COLLISION =======================================
  # =======================================================================
  def how_to_determine_collision args
    # Render the instructions
    args.nokia.labels << args.nokia
                              .default_label
                              .merge(x: 42,
                                     y: 46, text: "Click Anywhere",
                                     alignment_enum: 1)
  
    # if a mouse click occurs:
    # - set ship_one if it isn't set
    # - set ship_two if it isn't set
    # - otherwise reset ship one and ship two
    if args.nokia.mouse_click
      # is ship_one set?
      if !args.state.ship_one
        args.state.ship_one = { x: args.nokia.mouse_click.x - 5,
                                y: args.nokia.mouse_click.y - 5,
                                w: 10,
                                h: 10 }
      # is ship_one set?
      elsif !args.state.ship_two
        args.state.ship_two = { x: args.nokia.mouse_click.x - 5,
                                y: args.nokia.mouse_click.y - 5,
                                w: 10,
                                h: 10 }
      # should we reset?
      else
        args.state.ship_one = nil
        args.state.ship_two = nil
      end
    end
  
    # render ship one if it's set
    if args.state.ship_one
      # use Ruby's .merge method which is available on ~Hash~ to set the sprite and alpha
      # render ship one
      args.nokia.sprites << args.state.ship_one.merge(path: 'sprites/monochrome-ship.png')
    end
  
    if args.state.ship_two
      # use Ruby's .merge method which is available on ~Hash~ to set the sprite and alpha
      # render ship two
      args.nokia.sprites << args.state.ship_two.merge(path: 'sprites/monochrome-ship.png')
    end
  
    # if both ship one and ship two are set, then determine collision
    if args.state.ship_one && args.state.ship_two
      # collision is determined using the intersect_rect? method
      if args.state.ship_one.intersect_rect? args.state.ship_two
        # if collision occurred, render the words collision!
        args.nokia.labels << args.nokia
                              .default_label
                              .merge(x: 42,
                                     y: 5,
                                     text: "Collision!",
                                     alignment_enum: 1)
      else
        # if collision occurred, render the words no collision.
        args.nokia.labels << args.nokia
                              .default_label
                              .merge(x: 42,
                                     y: 5,
                                     text: "No Collision.",
                                     alignment_enum: 1)
      end
    else
      # if both ship one and ship two aren't set, then render --
        args.nokia.labels << args.nokia
                              .default_label
                              .merge(x: 42,
                                     y: 6,
                                     text: "--",
                                     alignment_enum: 1)
    end
  end
  
  # =============================================================================
  # ==== HOW TO CREATE BUTTONS ==================================================
  # =============================================================================
  def how_to_create_buttons args
    # Define a button style
    args.state.button_style = { w: 82, h: 10, }
  
    # Render instructions
    args.state.button_message ||= "Press a Button!"
    args.nokia.labels << args.nokia
                              .default_label
                              .merge(x: 42,
                                     y: 82,
                                     text: args.state.button_message,
                                     alignment_enum: 1)
  
  
    # Creates button one using a border and a label
    args.state.button_one_border = args.state.button_style.merge( x: 1, y: 32)
    args.nokia.borders << args.state.button_one_border
    args.nokia.labels  << args.nokia
                               .default_label
                               .merge(x: args.state.button_one_border.x + 2,
                                      y: args.state.button_one_border.y + NOKIA_FONT_SM_HEIGHT + 2,
                                      text: "Button One")
  
    # Creates button two using a border and a label
    args.state.button_two_border = args.state.button_style.merge( x: 1, y: 20)
  
    args.nokia.borders << args.state.button_two_border
    args.nokia.labels << args.nokia
                              .default_label
                              .merge(x: args.state.button_two_border.x + 2,
                                     y: args.state.button_two_border.y + NOKIA_FONT_SM_HEIGHT + 2,
                                     text: "Button Two")
  
    # Initialize the state variable that tracks which button was clicked to "" (empty stringI
    args.state.last_button_clicked ||= "--"
  
    # If a click occurs, check to see if either button one, or button two was clicked
    # using the inside_rect? method of the mouse
    # set args.state.last_button_clicked accordingly
    if args.nokia.mouse_click
      if args.nokia.mouse_click.inside_rect? args.state.button_one_border
        args.state.last_button_clicked = "One Clicked!"
      elsif args.nokia.mouse_click.inside_rect? args.state.button_two_border
        args.state.last_button_clicked = "Two Clicked!"
      else
        args.state.last_button_clicked = "--"
      end
    end
  
    # Render the current value of args.state.last_button_clicked
    args.nokia.labels << args.nokia
                               .default_label
                               .merge(x: 42,
                                      y: 5,
                                      text: args.state.last_button_clicked,
                                      alignment_enum: 1)
  end
  
  def render_debug args
    if !args.state.grid_rendered
      (NOKIA_HEIGHT + 1).map_with_index do |i|
        args.outputs.static_debug << {
          x:  NOKIA_X_OFFSET,
          y:  NOKIA_Y_OFFSET + (i * NOKIA_ZOOM),
          x2: NOKIA_X_OFFSET + NOKIA_ZOOMED_WIDTH,
          y2: NOKIA_Y_OFFSET + (i * NOKIA_ZOOM),
          r: 128,
          g: 128,
          b: 128,
          a: 80
        }.line
      end
  
      (NOKIA_WIDTH + 1).map_with_index do |i|
        args.outputs.static_debug << {
          x:  NOKIA_X_OFFSET + (i * NOKIA_ZOOM),
          y:  NOKIA_Y_OFFSET,
          x2: NOKIA_X_OFFSET + (i * NOKIA_ZOOM),
          y2: NOKIA_Y_OFFSET + NOKIA_ZOOMED_HEIGHT,
          r: 128,
          g: 128,
          b: 128,
          a: 80
        }.line
      end
    end
  
    args.state.grid_rendered = true
  
    args.state.last_click ||= 0
    args.state.last_up    ||= 0
    args.state.last_click   = args.state.tick_count if args.nokia.mouse_down # you can also use args.nokia.click
    args.state.last_up      = args.state.tick_count if args.nokia.mouse_up
    args.state.label_style  = { size_enum: -1.5 }
  
    args.state.watch_list = [
      "args.state.tick_count is:      #{args.state.tick_count}",
      "args.nokia.mouse_position is:  #{args.nokia.mouse_position.x}, #{args.nokia.mouse_position.y}",
      "args.nokia.mouse_down tick:    #{args.state.last_click || "never"}",
      "args.nokia.mouse_up tick:      #{args.state.last_up || "false"}",
    ]
  
    args.outputs.debug << args.state
                              .watch_list
                              .map_with_index do |text, i|
      {
        x: 5,
        y: 720 - (i * 18),
        text: text,
        size_enum: -1.5,
        r: 255, g: 255, b: 255
      }.label!
    end
  
    args.outputs.debug << {
      x: 640,
      y:  25,
      text: "INFO: dev mode is currently enabled. Comment out the invocation of ~render_debug~ within the ~tick~ method to hide the debug layer.",
      size_enum: -0.5,
      alignment_enum: 1,
      r: 255, g: 255, b: 255
    }.label!
  end
  
  def snake_demo args
  
  end
  
  $gtk.reset

#+end_src

*** Lowrez - Nokia 3310 - nokia.rb
#+begin_src ruby
  # ./samples/99_genre_lowrez/nokia_3310/app/nokia.rb
  # Emulation of a 64x64 canvas. Don't change this file unless you know what you're doing :-)
  # Head over to main.rb and study the code there.
  
  NOKIA_WIDTH           = 84
  NOKIA_HEIGHT          = 48
  NOKIA_ZOOM            = 12
  NOKIA_ZOOMED_WIDTH    = NOKIA_WIDTH  * NOKIA_ZOOM
  NOKIA_ZOOMED_HEIGHT   = NOKIA_HEIGHT * NOKIA_ZOOM
  NOKIA_X_OFFSET        = (1280 - NOKIA_ZOOMED_WIDTH).half
  NOKIA_Y_OFFSET        = ( 720 - NOKIA_ZOOMED_HEIGHT).half
  
  NOKIA_FONT_XL         = -1
  NOKIA_FONT_XL_HEIGHT  = 20
  
  NOKIA_FONT_LG         = -3.5
  NOKIA_FONT_LG_HEIGHT  = 15
  
  NOKIA_FONT_MD         = -6
  NOKIA_FONT_MD_HEIGHT  = 10
  
  NOKIA_FONT_SM         = -8.5
  NOKIA_FONT_SM_HEIGHT  = 5
  
  NOKIA_FONT_PATH       = 'fonts/lowrez.ttf'
  
  
  class NokiaOutputs
    attr_accessor :width, :height
  
    def initialize args
      @args = args
    end
  
    def outputs_nokia
      return @args.outputs if @args.state.tick_count <= 0
      return @args.outputs[:nokia]
    end
  
    def solids
      outputs_nokia.solids
    end
  
    def borders
      outputs_nokia.borders
    end
  
    def sprites
      outputs_nokia.sprites
    end
  
    def labels
      outputs_nokia.labels
    end
  
    def default_label
      {
        x: 0,
        y: 63,
        text: "",
        size_enum: NOKIA_FONT_SM,
        alignment_enum: 0,
        r: 0,
        g: 0,
        b: 0,
        a: 255,
        font: NOKIA_FONT_PATH
      }
    end
  
    def lines
      outputs_nokia.lines
    end
  
    def primitives
      outputs_nokia.primitives
    end
  
    def click
      return nil unless @args.inputs.mouse.click
      mouse
    end
  
    def mouse_click
      click
    end
  
    def mouse_down
      @args.inputs.mouse.down
    end
  
    def mouse_up
      @args.inputs.mouse.up
    end
  
    def mouse
      [
        ((@args.inputs.mouse.x - NOKIA_X_OFFSET).idiv(NOKIA_ZOOM)),
        ((@args.inputs.mouse.y - NOKIA_Y_OFFSET).idiv(NOKIA_ZOOM))
      ]
    end
  
    def mouse_position
      mouse
    end
  
    def keyboard
      @args.inputs.keyboard
    end
  end
  
  class GTK::Args
    def init_nokia
      return if @nokia
      @nokia = NokiaOutputs.new self
    end
  
    def nokia
      @nokia
    end
  end
  
  module GTK
    class Runtime
      alias_method :__original_tick_core__, :tick_core unless Runtime.instance_methods.include?(:__original_tick_core__)
  
      def tick_core
        @args.init_nokia
  
        __original_tick_core__
  
        return if @args.state.tick_count <= 0
  
        @args.render_target(:nokia)
             .labels
             .each do |l|
          l.y  += 1
          if (l.a || 255) > 128
            l.r = 67
            l.g = 82
            l.b = 61
            l.a = 255
          else
            l.a = 0
          end
        end
  
        @args.render_target(:nokia)
             .sprites
             .each do |s|
          if (s.a || 255) > 128
            s.a = 255
          else
            s.a = 0
          end
        end
  
        @args.render_target(:nokia)
             .solids
             .each do |s|
          if (s.a || 255) > 128
            s.r = 67
            s.g = 82
            s.b = 61
            s.a = 255
          else
            s.a = 0
          end
        end
  
        @args.render_target(:nokia)
             .borders
             .each do |s|
          if (s.a || 255) > 128
            s.r = 67
            s.g = 82
            s.b = 61
            s.a = 255
          else
            s.a = 0
          end
        end
  
        @args.render_target(:nokia)
             .lines
             .each do |l|
          l.y  += 1
          l.y2 += 1
          l.y2 += 1 if l.y1 != l.y2
          l.x2 += 1 if l.x1 != l.x2
  
          if (l.a || 255) > 128
            l.r = 67
            l.g = 82
            l.b = 61
            l.a = 255
          else
            l.a = 0
          end
        end
  
        @args.outputs.borders << {
          x: NOKIA_X_OFFSET      - 1,
          y: NOKIA_Y_OFFSET      - 1,
          w: NOKIA_ZOOMED_WIDTH  + 2,
          h: NOKIA_ZOOMED_HEIGHT + 2,
          r: 128, g: 128, b: 128
        }
  
  
        @args.outputs.background_color = [199, 240, 216]
  
        @args.outputs.solids << [0, 0, NOKIA_X_OFFSET, 720]
        @args.outputs.solids << [0, 0, 1280, NOKIA_Y_OFFSET]
        @args.outputs.solids << [NOKIA_X_OFFSET + NOKIA_ZOOMED_WIDTH, 0, NOKIA_X_OFFSET, 720]
        @args.outputs.solids << [0, NOKIA_Y_OFFSET.from_top, 1280, NOKIA_Y_OFFSET]
  
        @args.outputs
             .sprites << { x: NOKIA_X_OFFSET,
                           y: NOKIA_Y_OFFSET,
                           w: NOKIA_ZOOMED_WIDTH,
                           h: NOKIA_ZOOMED_HEIGHT,
                           source_x: 0,
                           source_y: 0,
                           source_w: NOKIA_WIDTH,
                           source_h: NOKIA_HEIGHT,
                           path: :nokia }
  
        if !@args.state.overlay_rendered
          (NOKIA_HEIGHT + 1).map_with_index do |i|
            @args.outputs.static_lines << {
              x:  NOKIA_X_OFFSET,
              y:  NOKIA_Y_OFFSET + (i * NOKIA_ZOOM),
              x2: NOKIA_X_OFFSET + NOKIA_ZOOMED_WIDTH,
              y2: NOKIA_Y_OFFSET + (i * NOKIA_ZOOM),
              r: 199,
              g: 240,
              b: 216,
              a: 100
            }.line!
          end
  
          (NOKIA_WIDTH + 1).map_with_index do |i|
            @args.outputs.static_lines << {
              x:  NOKIA_X_OFFSET + (i * NOKIA_ZOOM),
              y:  NOKIA_Y_OFFSET,
              x2: NOKIA_X_OFFSET + (i * NOKIA_ZOOM),
              y2: NOKIA_Y_OFFSET + NOKIA_ZOOMED_HEIGHT,
              r: 199,
              g: 240,
              b: 216,
              a: 100
            }.line!
          end
  
          @args.state.overlay_rendered = true
        end
      end
    end
  end

#+end_src

*** Lowrez - Resolution 64x64 - lowrez.rb
#+begin_src ruby
  # ./samples/99_genre_lowrez/resolution_64x64/app/lowrez.rb
  # Emulation of a 64x64 canvas. Don't change this file unless you know what you're doing :-)
  # Head over to main.rb and study the code there.
  
  LOWREZ_SIZE            = 64
  LOWREZ_ZOOM            = 10
  LOWREZ_ZOOMED_SIZE     = LOWREZ_SIZE * LOWREZ_ZOOM
  LOWREZ_X_OFFSET        = (1280 - LOWREZ_ZOOMED_SIZE).half
  LOWREZ_Y_OFFSET        = ( 720 - LOWREZ_ZOOMED_SIZE).half
  
  LOWREZ_FONT_XL         = -1
  LOWREZ_FONT_XL_HEIGHT  = 20
  
  LOWREZ_FONT_LG         = -3.5
  LOWREZ_FONT_LG_HEIGHT  = 15
  
  LOWREZ_FONT_MD         = -6
  LOWREZ_FONT_MD_HEIGHT  = 10
  
  LOWREZ_FONT_SM         = -8.5
  LOWREZ_FONT_SM_HEIGHT  = 5
  
  LOWREZ_FONT_PATH       = 'fonts/lowrez.ttf'
  
  
  class LowrezOutputs
    attr_accessor :width, :height
  
    def initialize args
      @args = args
      @background_color ||= [0, 0, 0]
      @args.outputs.background_color = @background_color
    end
  
    def background_color
      @background_color ||= [0, 0, 0]
    end
  
    def background_color= opts
      @background_color = opts
      @args.outputs.background_color = @background_color
  
      outputs_lowrez.solids << [0, 0, LOWREZ_SIZE, LOWREZ_SIZE, @background_color]
    end
  
    def outputs_lowrez
      return @args.outputs if @args.state.tick_count <= 0
      return @args.outputs[:lowrez]
    end
  
    def solids
      outputs_lowrez.solids
    end
  
    def borders
      outputs_lowrez.borders
    end
  
    def sprites
      outputs_lowrez.sprites
    end
  
    def labels
      outputs_lowrez.labels
    end
  
    def default_label
      {
        x: 0,
        y: 63,
        text: "",
        size_enum: LOWREZ_FONT_SM,
        alignment_enum: 0,
        r: 0,
        g: 0,
        b: 0,
        a: 255,
        font: LOWREZ_FONT_PATH
      }
    end
  
    def lines
      outputs_lowrez.lines
    end
  
    def primitives
      outputs_lowrez.primitives
    end
  
    def click
      return nil unless @args.inputs.mouse.click
      mouse
    end
  
    def mouse_click
      click
    end
  
    def mouse_down
      @args.inputs.mouse.down
    end
  
    def mouse_up
      @args.inputs.mouse.up
    end
  
    def mouse
      [
        ((@args.inputs.mouse.x - LOWREZ_X_OFFSET).idiv(LOWREZ_ZOOM)),
        ((@args.inputs.mouse.y - LOWREZ_Y_OFFSET).idiv(LOWREZ_ZOOM))
      ]
    end
  
    def mouse_position
      mouse
    end
  
    def keyboard
      @args.inputs.keyboard
    end
  end
  
  class GTK::Args
    def init_lowrez
      return if @lowrez
      @lowrez = LowrezOutputs.new self
    end
  
    def lowrez
      @lowrez
    end
  end
  
  module GTK
    class Runtime
      alias_method :__original_tick_core__, :tick_core unless Runtime.instance_methods.include?(:__original_tick_core__)
  
      def tick_core
        @args.init_lowrez
        __original_tick_core__
  
        return if @args.state.tick_count <= 0
  
        @args.render_target(:lowrez)
             .labels
             .each do |l|
          l.y  += 1
        end
  
        @args.render_target(:lowrez)
             .lines
             .each do |l|
          l.y  += 1
          l.y2 += 1
          l.y2 += 1 if l.y1 != l.y2
          l.x2 += 1 if l.x1 != l.x2
        end
  
        @args.outputs
             .sprites << { x: 320,
                           y: 40,
                           w: 640,
                           h: 640,
                           source_x: 0,
                           source_y: 0,
                           source_w: 64,
                           source_h: 64,
                           path: :lowrez }
      end
    end
  end

#+end_src

*** Lowrez - Resolution 64x64 - main.rb
#+begin_src ruby
  # ./samples/99_genre_lowrez/resolution_64x64/app/main.rb
  require 'app/lowrez.rb'
  
  def tick args
    # How to set the background color
    args.lowrez.background_color = [255, 255, 255]
  
    # ==== HELLO WORLD ======================================================
    # Steps to get started:
    # 1. ~def tick args~ is the entry point for your game.
    # 2. There are quite a few code samples below, remove the "##"
    #    before each line and save the file to see the changes.
    # 3. 0,  0 is in bottom left and 63, 63 is in top right corner.
    # 4. Be sure to come to the discord channel if you need
    #    more help: [[http://discord.dragonruby.org]].
  
    # Commenting and uncommenting code:
    # - Add a "#" infront of lines to comment out code
    # - Remove the "#" infront of lines to comment out code
  
    # Invoke the hello_world subroutine/method
    hello_world args # <---- add a "#" to the beginning of the line to stop running this subroutine/method.
    # =======================================================================
  
  
    # ==== HOW TO RENDER A LABEL ============================================
    # Uncomment the line below to invoke the how_to_render_a_label subroutine/method.
    # Note: The method is defined in this file with the signature ~def how_to_render_a_label args~
    #       Scroll down to the method to see the details.
  
    # Remove the "#" at the beginning of the line below
    # how_to_render_a_label args # <---- remove the "#" at the begging of this line to run the method
    # =======================================================================
  
  
    # ==== HOW TO RENDER A FILLED SQUARE (SOLID) ============================
    # Remove the "#" at the beginning of the line below
    # how_to_render_solids args
    # =======================================================================
  
  
    # ==== HOW TO RENDER AN UNFILLED SQUARE (BORDER) ========================
    # Remove the "#" at the beginning of the line below
    # how_to_render_borders args
    # =======================================================================
  
  
    # ==== HOW TO RENDER A LINE =============================================
    # Remove the "#" at the beginning of the line below
    # how_to_render_lines args
    # =======================================================================
  
  
    # == HOW TO RENDER A SPRITE =============================================
    # Remove the "#" at the beginning of the line below
    # how_to_render_sprites args
    # =======================================================================
  
  
    # ==== HOW TO MOVE A SPRITE BASED OFF OF USER INPUT =====================
    # Remove the "#" at the beginning of the line below
    # how_to_move_a_sprite args
    # =======================================================================
  
  
    # ==== HOW TO ANIMATE A SPRITE (SEPERATE PNGS) ==========================
    # Remove the "#" at the beginning of the line below
    # how_to_animate_a_sprite args
    # =======================================================================
  
  
    # ==== HOW TO ANIMATE A SPRITE (SPRITE SHEET) ===========================
    # Remove the "#" at the beginning of the line below
    # how_to_animate_a_sprite_sheet args
    # =======================================================================
  
  
    # ==== HOW TO DETERMINE COLLISION =============================================
    # Remove the "#" at the beginning of the line below
    # how_to_determine_collision args
    # =======================================================================
  
  
    # ==== HOW TO CREATE BUTTONS ==================================================
    # Remove the "#" at the beginning of the line below
    # how_to_create_buttons args
    # =======================================================================
  
  
    # ==== The line below renders a debug grid, mouse information, and current tick
    render_debug args
  end
  
  def hello_world args
    args.lowrez.solids  << { x: 0, y: 64, w: 10, h: 10, r: 255 }
  
    args.lowrez.labels  << {
      x: 32,
      y: 63,
      text: "lowrezjam 2020",
      size_enum: LOWREZ_FONT_SM,
      alignment_enum: 1,
      r: 0,
      g: 0,
      b: 0,
      a: 255,
      font: LOWREZ_FONT_PATH
    }
  
    args.lowrez.sprites << {
      x: 32 - 10,
      y: 32 - 10,
      w: 20,
      h: 20,
      path: 'sprites/lowrez-ship-blue.png',
      a: args.state.tick_count % 255,
      angle: args.state.tick_count % 360
    }
  end
  
  
  # =======================================================================
  # ==== HOW TO RENDER A LABEL ============================================
  # =======================================================================
  def how_to_render_a_label args
    # NOTE: Text is aligned from the TOP LEFT corner
  
    # Render an EXTRA LARGE/XL label (remove the "#" in front of each line below)
    args.lowrez.labels << { x: 0, y: 57, text: "Hello World",
                           size_enum: LOWREZ_FONT_XL,
                           r: 0, g: 0, b: 0, a: 255,
                           font: LOWREZ_FONT_PATH }
  
    # Render a LARGE/LG label (remove the "#" in front of each line below)
    args.lowrez.labels << { x: 0, y: 36, text: "Hello World",
                            size_enum: LOWREZ_FONT_LG,
                            r: 0, g: 0, b: 0, a: 255,
                            font: LOWREZ_FONT_PATH }
  
    # Render a MEDIUM/MD label (remove the "#" in front of each line below)
    args.lowrez.labels << { x: 0, y: 20, text: "Hello World",
                            size_enum: LOWREZ_FONT_MD,
                            r: 0, g: 0, b: 0, a: 255,
                            font: LOWREZ_FONT_PATH }
  
    # Render a SMALL/SM label (remove the "#" in front of each line below)
    args.lowrez.labels << { x: 0, y: 9, text: "Hello World",
                            size_enum: LOWREZ_FONT_SM,
                            r: 0, g: 0, b: 0, a: 255,
                            font: LOWREZ_FONT_PATH }
  
    # You are provided args.lowrez.default_label which returns a Hash that you
    # can ~merge~ properties with
    # Example 1
    args.lowrez.labels << args.lowrez
                              .default_label
                              .merge(text: "Default")
  
    # Example 2
    args.lowrez.labels << args.lowrez
                              .default_label
                              .merge(x: 31,
                                     text: "Default",
                                     r: 128,
                                     g: 128,
                                     b: 128)
  end
  
  ## # =============================================================================
  ## # ==== HOW TO RENDER FILLED SQUARES (SOLIDS) ==================================
  ## # =============================================================================
  def how_to_render_solids args
    # Render a red square at 0, 0 with a width and height of 1
    args.lowrez.solids << { x: 0, y: 0, w: 1, h: 1, r: 255, g: 0, b: 0, a: 255 }
  
    # Render a red square at 1, 1 with a width and height of 2
    args.lowrez.solids << { x: 1, y: 1, w: 2, h: 2, r: 255, g: 0, b: 0, a: 255 }
  
    # Render a red square at 3, 3 with a width and height of 3
    args.lowrez.solids << { x: 3, y: 3, w: 3, h: 3, r: 255, g: 0, b: 0 }
  
    # Render a red square at 6, 6 with a width and height of 4
    args.lowrez.solids << { x: 6, y: 6, w: 4, h: 4, r: 255, g: 0, b: 0 }
  end
  
  ## # =============================================================================
  ## # ==== HOW TO RENDER UNFILLED SQUARES (BORDERS) ===============================
  ## # =============================================================================
  def how_to_render_borders args
    # Render a red square at 0, 0 with a width and height of 3
    args.lowrez.borders << { x: 0, y: 0, w: 3, h: 3, r: 255, g: 0, b: 0, a: 255 }
  
    # Render a red square at 3, 3 with a width and height of 3
    args.lowrez.borders << { x: 3, y: 3, w: 4, h: 4, r: 255, g: 0, b: 0, a: 255 }
  
    # Render a red square at 5, 5 with a width and height of 4
    args.lowrez.borders << { x: 7, y: 7, w: 5, h: 5, r: 255, g: 0, b: 0, a: 255 }
  end
  
  ## # =============================================================================
  ## # ==== HOW TO RENDER A LINE ===================================================
  ## # =============================================================================
  def how_to_render_lines args
    # Render a horizontal line at the bottom
    args.lowrez.lines << { x: 0, y: 0, x2: 63, y2:  0, r: 255 }
  
    # Render a vertical line at the left
    args.lowrez.lines << { x: 0, y: 0, x2:  0, y2: 63, r: 255 }
  
    # Render a diagonal line starting from the bottom left and going to the top right
    args.lowrez.lines << { x: 0, y: 0, x2: 63, y2: 63, r: 255 }
  end
  
  ## # =============================================================================
  ## # == HOW TO RENDER A SPRITE ===================================================
  ## # =============================================================================
  def how_to_render_sprites args
    # Loop 10 times and create 10 sprites in 10 positions
    # Render a sprite at the bottom left with a width and height of 5 and a path of 'sprites/lowrez-ship-blue.png'
    10.times do |i|
      args.lowrez.sprites << {
        x: i * 5,
        y: i * 5,
        w: 5,
        h: 5,
        path: 'sprites/lowrez-ship-blue.png'
      }
    end
  
    # Given an array of positions create sprites
    positions = [
      { x: 10, y: 42 },
      { x: 15, y: 45 },
      { x: 22, y: 33 },
    ]
  
    positions.each do |position|
      # use Ruby's ~Hash#merge~ function to create a sprite
      args.lowrez.sprites << position.merge(path: 'sprites/lowrez-ship-red.png',
                                            w: 5,
                                            h: 5)
    end
  end
  
  ## # =============================================================================
  ## # ==== HOW TO ANIMATE A SPRITE (SEPERATE PNGS) ==========================
  ## # =============================================================================
  def how_to_animate_a_sprite args
    # STEP 1: Define when you want the animation to start. The animation in this case will start in 3 seconds
    start_animation_on_tick = 180
  
    # STEP 2: Get the frame_index given the start tick.
    sprite_index = start_animation_on_tick.frame_index count: 7,     # how many sprites?
                                                       hold_for: 4,  # how long to hold each sprite?
                                                       repeat: true  # should it repeat?
  
    # STEP 3: frame_index will return nil if the frame hasn't arrived yet
    if sprite_index
      # if the sprite_index is populated, use it to determine the sprite path and render it
      sprite_path  = "sprites/explosion-#{sprite_index}.png"
      args.lowrez.sprites << { x: 0, y: 0, w: 64, h: 64, path: sprite_path }
    else
      # if the sprite_index is nil, render a countdown instead
      countdown_in_seconds = ((start_animation_on_tick - args.state.tick_count) / 60).round(1)
  
      args.lowrez.labels  << args.lowrez
                                 .default_label
                                 .merge(x: 32,
                                        y: 32,
                                        text: "Count Down: #{countdown_in_seconds}",
                                        alignment_enum: 1)
    end
  
    # render the current tick and the resolved sprite index
    args.lowrez.labels  << args.lowrez
                                 .default_label
                                 .merge(x: 0,
                                        y: 11,
                                        text: "Tick: #{args.state.tick_count}")
    args.lowrez.labels  << args.lowrez
                                 .default_label
                                 .merge(x: 0,
                                        y: 5,
                                        text: "sprite_index: #{sprite_index}")
  end
  
  ## # =============================================================================
  ## # ==== HOW TO ANIMATE A SPRITE (SPRITE SHEET) =================================
  ## # =============================================================================
  def how_to_animate_a_sprite_sheet args
    # STEP 1: Define when you want the animation to start. The animation in this case will start in 3 seconds
    start_animation_on_tick = 180
  
    # STEP 2: Get the frame_index given the start tick.
    sprite_index = start_animation_on_tick.frame_index count: 7,     # how many sprites?
                                                       hold_for: 4,  # how long to hold each sprite?
                                                       repeat: true  # should it repeat?
  
    # STEP 3: frame_index will return nil if the frame hasn't arrived yet
    if sprite_index
      # if the sprite_index is populated, use it to determine the source rectangle and render it
      args.lowrez.sprites << {
        x: 0,
        y: 0,
        w: 64,
        h: 64,
        path:  "sprites/explosion-sheet.png",
        source_x: 32 * sprite_index,
        source_y: 0,
        source_w: 32,
        source_h: 32
      }
    else
      # if the sprite_index is nil, render a countdown instead
      countdown_in_seconds = ((start_animation_on_tick - args.state.tick_count) / 60).round(1)
  
      args.lowrez.labels  << args.lowrez
                                 .default_label
                                 .merge(x: 32,
                                        y: 32,
                                        text: "Count Down: #{countdown_in_seconds}",
                                        alignment_enum: 1)
    end
  
    # render the current tick and the resolved sprite index
    args.lowrez.labels  << args.lowrez
                                 .default_label
                                 .merge(x: 0,
                                        y: 11,
                                        text: "tick: #{args.state.tick_count}")
    args.lowrez.labels  << args.lowrez
                                 .default_label
                                 .merge(x: 0,
                                        y: 5,
                                        text: "sprite_index: #{sprite_index}")
  end
  
  ## # =============================================================================
  ## # ==== HOW TO STORE STATE, ACCEPT INPUT, AND RENDER SPRITE BASED OFF OF STATE =
  ## # =============================================================================
  def how_to_move_a_sprite args
    args.lowrez.labels << args.lowrez
                              .default_label
                              .merge(x: 32,
                                     y: 62, text: "Use Arrow Keys",
                                     alignment_enum: 1)
  
    args.lowrez.labels << args.lowrez
                              .default_label
                              .merge(x: 32,
                                     y: 56, text: "Use WASD",
                                     alignment_enum: 1)
  
    args.lowrez.labels << args.lowrez
                              .default_label
                              .merge(x: 32,
                                     y: 50, text: "Or Click",
                                     alignment_enum: 1)
  
    # set the initial values for x and y using ||= ("or equal operator")
    args.state.ship.x ||= 0
    args.state.ship.y ||= 0
  
    # if a mouse click occurs, update the ship's x and y to be the location of the click
    if args.lowrez.mouse_click
      args.state.ship.x = args.lowrez.mouse_click.x
      args.state.ship.y = args.lowrez.mouse_click.y
    end
  
    # if a or left arrow is pressed/held, decrement the ships x position
    if args.lowrez.keyboard.left
      args.state.ship.x -= 1
    end
  
    # if d or right arrow is pressed/held, increment the ships x position
    if args.lowrez.keyboard.right
      args.state.ship.x += 1
    end
  
    # if s or down arrow is pressed/held, decrement the ships y position
    if args.lowrez.keyboard.down
      args.state.ship.y -= 1
    end
  
    # if w or up arrow is pressed/held, increment the ships y position
    if args.lowrez.keyboard.up
      args.state.ship.y += 1
    end
  
    # render the sprite to the screen using the position stored in args.state.ship
    args.lowrez.sprites << {
      x: args.state.ship.x,
      y: args.state.ship.y,
      w: 5,
      h: 5,
      path: 'sprites/lowrez-ship-blue.png',
      # parameters beyond this point are optional
      angle: 0, # Note: rotation angle is denoted in degrees NOT radians
      r: 255,
      g: 255,
      b: 255,
      a: 255
    }
  end
  
  # =======================================================================
  # ==== HOW TO DETERMINE COLLISION =======================================
  # =======================================================================
  def how_to_determine_collision args
    # Render the instructions
    args.lowrez.labels << args.lowrez
                              .default_label
                              .merge(x: 32,
                                     y: 62, text: "Click Anywhere",
                                     alignment_enum: 1)
  
    # if a mouse click occurs:
    # - set ship_one if it isn't set
    # - set ship_two if it isn't set
    # - otherwise reset ship one and ship two
    if args.lowrez.mouse_click
      # is ship_one set?
      if !args.state.ship_one
        args.state.ship_one = { x: args.lowrez.mouse_click.x - 10,
                                y: args.lowrez.mouse_click.y - 10,
                                w: 20,
                                h: 20 }
      # is ship_one set?
      elsif !args.state.ship_two
        args.state.ship_two = { x: args.lowrez.mouse_click.x - 10,
                                y: args.lowrez.mouse_click.y - 10,
                                w: 20,
                                h: 20 }
      # should we reset?
      else
        args.state.ship_one = nil
        args.state.ship_two = nil
      end
    end
  
    # render ship one if it's set
    if args.state.ship_one
      # use Ruby's .merge method which is available on ~Hash~ to set the sprite and alpha
      # render ship one
      args.lowrez.sprites << args.state.ship_one.merge(path: 'sprites/lowrez-ship-blue.png', a: 100)
    end
  
    if args.state.ship_two
      # use Ruby's .merge method which is available on ~Hash~ to set the sprite and alpha
      # render ship two
      args.lowrez.sprites << args.state.ship_two.merge(path: 'sprites/lowrez-ship-red.png', a: 100)
    end
  
    # if both ship one and ship two are set, then determine collision
    if args.state.ship_one && args.state.ship_two
      # collision is determined using the intersect_rect? method
      if args.state.ship_one.intersect_rect? args.state.ship_two
        # if collision occurred, render the words collision!
        args.lowrez.labels << args.lowrez
                              .default_label
                              .merge(x: 31,
                                     y: 5,
                                     text: "Collision!",
                                     alignment_enum: 1)
      else
        # if collision occurred, render the words no collision.
        args.lowrez.labels << args.lowrez
                              .default_label
                              .merge(x: 31,
                                     y: 5,
                                     text: "No Collision.",
                                     alignment_enum: 1)
      end
    else
      # if both ship one and ship two aren't set, then render --
        args.lowrez.labels << args.lowrez
                              .default_label
                              .merge(x: 31,
                                     y: 6,
                                     text: "--",
                                     alignment_enum: 1)
    end
  end
  
  ## # =============================================================================
  ## # ==== HOW TO CREATE BUTTONS ==================================================
  ## # =============================================================================
  def how_to_create_buttons args
    # Define a button style
    args.state.button_style = { w: 62, h: 10, r: 80, g: 80, b: 80 }
    args.state.label_style  = { r: 80, g: 80, b: 80 }
  
    # Render instructions
    args.state.button_message ||= "Press a Button!"
    args.lowrez.labels << args.lowrez
                              .default_label
                              .merge(args.state.label_style)
                              .merge(x: 32,
                                     y: 62,
                                     text: args.state.button_message,
                                     alignment_enum: 1)
  
  
    # Creates button one using a border and a label
    args.state.button_one_border = args.state.button_style.merge( x: 1, y: 32)
    args.lowrez.borders << args.state.button_one_border
    args.lowrez.labels  << args.lowrez
                               .default_label
                               .merge(args.state.label_style)
                               .merge(x: args.state.button_one_border.x + 2,
                                      y: args.state.button_one_border.y + LOWREZ_FONT_SM_HEIGHT + 2,
                                      text: "Button One")
  
    # Creates button two using a border and a label
    args.state.button_two_border = args.state.button_style.merge( x: 1, y: 20)
  
    args.lowrez.borders << args.state.button_two_border
    args.lowrez.labels << args.lowrez
                              .default_label
                              .merge(args.state.label_style)
                              .merge(x: args.state.button_two_border.x + 2,
                                     y: args.state.button_two_border.y + LOWREZ_FONT_SM_HEIGHT + 2,
                                     text: "Button Two")
  
    # Initialize the state variable that tracks which button was clicked to "" (empty stringI
    args.state.last_button_clicked ||= "--"
  
    # If a click occurs, check to see if either button one, or button two was clicked
    # using the inside_rect? method of the mouse
    # set args.state.last_button_clicked accordingly
    if args.lowrez.mouse_click
      if args.lowrez.mouse_click.inside_rect? args.state.button_one_border
        args.state.last_button_clicked = "One Clicked!"
      elsif args.lowrez.mouse_click.inside_rect? args.state.button_two_border
        args.state.last_button_clicked = "Two Clicked!"
      else
        args.state.last_button_clicked = "--"
      end
    end
  
    # Render the current value of args.state.last_button_clicked
    args.lowrez.labels << args.lowrez
                               .default_label
                               .merge(args.state.label_style)
                               .merge(x: 32,
                                      y: 5,
                                      text: args.state.last_button_clicked,
                                      alignment_enum: 1)
  end
  
  
  def render_debug args
    if !args.state.grid_rendered
      65.map_with_index do |i|
        args.outputs.static_debug << {
          x:  LOWREZ_X_OFFSET,
          y:  LOWREZ_Y_OFFSET + (i * 10),
          x2: LOWREZ_X_OFFSET + LOWREZ_ZOOMED_SIZE,
          y2: LOWREZ_Y_OFFSET + (i * 10),
          r: 128,
          g: 128,
          b: 128,
          a: 80
        }.line!
  
        args.outputs.static_debug << {
          x:  LOWREZ_X_OFFSET + (i * 10),
          y:  LOWREZ_Y_OFFSET,
          x2: LOWREZ_X_OFFSET + (i * 10),
          y2: LOWREZ_Y_OFFSET + LOWREZ_ZOOMED_SIZE,
          r: 128,
          g: 128,
          b: 128,
          a: 80
        }.line!
      end
    end
  
    args.state.grid_rendered = true
  
    args.state.last_click ||= 0
    args.state.last_up    ||= 0
    args.state.last_click   = args.state.tick_count if args.lowrez.mouse_down # you can also use args.lowrez.click
    args.state.last_up      = args.state.tick_count if args.lowrez.mouse_up
    args.state.label_style  = { size_enum: -1.5 }
  
    args.state.watch_list = [
      "args.state.tick_count is:       #{args.state.tick_count}",
      "args.lowrez.mouse_position is:  #{args.lowrez.mouse_position.x}, #{args.lowrez.mouse_position.y}",
      "args.lowrez.mouse_down tick:    #{args.state.last_click || "never"}",
      "args.lowrez.mouse_up tick:      #{args.state.last_up || "false"}",
    ]
  
    args.outputs.debug << args.state
                              .watch_list
                              .map_with_index do |text, i|
      {
        x: 5,
        y: 720 - (i * 20),
        text: text,
        size_enum: -1.5
      }.label!
    end
  
    args.outputs.debug << {
      x: 640,
      y:  25,
      text: "INFO: dev mode is currently enabled. Comment out the invocation of ~render_debug~ within the ~tick~ method to hide the debug layer.",
      size_enum: -0.5,
      alignment_enum: 1
    }.label!
  end
  
  $gtk.reset

#+end_src

*** Mario - Jumping - main.rb
#+begin_src ruby
  # ./samples/99_genre_mario/01_jumping/app/main.rb
  def tick args
    defaults args
    render args
    input args
    calc args
  end
  
  def defaults args
    args.state.player.x      ||= args.grid.w.half
    args.state.player.y      ||= 0
    args.state.player.size   ||= 100
    args.state.player.dy     ||= 0
    args.state.player.action ||= :jumping
    args.state.jump.power           = 20
    args.state.jump.increase_frames = 10
    args.state.jump.increase_power  = 1
    args.state.gravity              = -1
  end
  
  def render args
    args.outputs.sprites << {
      x: args.state.player.x -
         args.state.player.size.half,
      y: args.state.player.y,
      w: args.state.player.size,
      h: args.state.player.size,
      path: 'sprites/square/red.png'
    }
  end
  
  def input args
    if args.inputs.keyboard.key_down.space
      if args.state.player.action == :standing
        args.state.player.action = :jumping
        args.state.player.dy = args.state.jump.power
  
        # record when the action took place
        current_frame = args.state.tick_count
        args.state.player.action_at = current_frame
      end
    end
  
    # if the space bar is being held
    if args.inputs.keyboard.key_held.space
      # is the player jumping
      is_jumping = args.state.player.action == :jumping
  
      # when was the jump performed
      time_of_jump = args.state.player.action_at
  
      # how much time has passed since the jump
      jump_elapsed_time = time_of_jump.elapsed_time
  
      # how much time is allowed for increasing power
      time_allowed = args.state.jump.increase_frames
  
      # if the player is jumping
      # and the elapsed time is less than
      # the allowed time
      if is_jumping && jump_elapsed_time < time_allowed
         # increase the dy by the increase power
         power_to_add = args.state.jump.increase_power
         args.state.player.dy += power_to_add
      end
    end
  end
  
  def calc args
    if args.state.player.action == :jumping
      args.state.player.y  += args.state.player.dy
      args.state.player.dy += args.state.gravity
    end
  
    if args.state.player.y < 0
      args.state.player.y      = 0
      args.state.player.action = :standing
    end
  end

#+end_src

*** Mario - Jumping And Collisions - main.rb
#+begin_src ruby
  # ./samples/99_genre_mario/02_jumping_and_collisions/app/main.rb
  class Game
    attr_gtk
  
    def tick
      defaults
      render
      input
      calc
    end
  
    def defaults
      return if state.tick_count != 0
  
      player.x                     = 64
      player.y                     = 800
      player.size                  = 50
      player.dx                    = 0
      player.dy                    = 0
      player.action                = :falling
  
      player.max_speed             = 20
      player.jump_power            = 15
      player.jump_air_time         = 15
      player.jump_increase_power   = 1
  
      state.gravity                = -1
      state.drag                   = 0.001
      state.tile_size              = 64
      state.tiles                ||= [
        { ordinal_x:  0, ordinal_y: 0 },
        { ordinal_x:  1, ordinal_y: 0 },
        { ordinal_x:  2, ordinal_y: 0 },
        { ordinal_x:  3, ordinal_y: 0 },
        { ordinal_x:  4, ordinal_y: 0 },
        { ordinal_x:  5, ordinal_y: 0 },
        { ordinal_x:  6, ordinal_y: 0 },
        { ordinal_x:  7, ordinal_y: 0 },
        { ordinal_x:  8, ordinal_y: 0 },
        { ordinal_x:  9, ordinal_y: 0 },
        { ordinal_x: 10, ordinal_y: 0 },
        { ordinal_x: 11, ordinal_y: 0 },
        { ordinal_x: 12, ordinal_y: 0 },
  
        { ordinal_x:  9, ordinal_y: 3 },
        { ordinal_x: 10, ordinal_y: 3 },
        { ordinal_x: 11, ordinal_y: 3 },
      ]
  
      tiles.each do |t|
        t.rect = { x: t.ordinal_x * 64,
                   y: t.ordinal_y * 64,
                   w: 64,
                   h: 64 }
      end
    end
  
    def render
      render_player
      render_tiles
      # render_grid
    end
  
    def input
      input_jump
      input_move
    end
  
    def calc
      calc_player_rect
      calc_left
      calc_right
      calc_below
      calc_above
      calc_player_dy
      calc_player_dx
      calc_game_over
    end
  
    def render_player
      outputs.sprites << {
        x: player.x,
        y: player.y,
        w: player.size,
        h: player.size,
        path: 'sprites/square/red.png'
      }
    end
  
    def render_tiles
      outputs.sprites << state.tiles.map do |t|
        t.merge path: 'sprites/square/white.png',
                x: t.ordinal_x * 64,
                y: t.ordinal_y * 64,
                w: 64,
                h: 64
      end
    end
  
    def render_grid
      if state.tick_count == 0
        outputs[:grid].background_color = [0, 0, 0, 0]
        outputs[:grid].borders << available_brick_locations
        outputs[:grid].labels  << available_brick_locations.map do |b|
          [
            b.merge(text: "#{b.ordinal_x},#{b.ordinal_y}",
                    x: b.x + 2,
                    y: b.y + 2,
                    size_enum: -3,
                    vertical_alignment_enum: 0,
                    blendmode_enum: 0),
            b.merge(text: "#{b.x},#{b.y}",
                    x: b.x + 2,
                    y: b.y + 2 + 20,
                    size_enum: -3,
                    vertical_alignment_enum: 0,
                    blendmode_enum: 0)
          ]
        end
      end
  
      outputs.sprites << { x: 0, y: 0, w: 1280, h: 720, path: :grid }
    end
  
    def input_jump
      if inputs.keyboard.key_down.space
        player_jump
      end
  
      if inputs.keyboard.key_held.space
        player_jump_increase_air_time
      end
    end
  
    def input_move
      if player.dx.abs < 20
        if inputs.keyboard.left
          player.dx -= 2
        elsif inputs.keyboard.right
          player.dx += 2
        end
      end
    end
  
    def calc_game_over
      if player.y < -64
        player.x = 64
        player.y = 800
        player.dx = 0
        player.dy = 0
      end
    end
  
    def calc_player_rect
      player.rect      = player_current_rect
      player.next_rect = player_next_rect
      player.prev_rect = player_prev_rect
    end
  
    def calc_player_dx
      player.dx  = player_next_dx
      player.x  += player.dx
    end
  
    def calc_player_dy
      player.y  += player.dy
      player.dy  = player_next_dy
    end
  
    def calc_below
      return unless player.dy < 0
      tiles_below = tiles_find { |t| t.rect.top <= player.prev_rect.y }
      collision = tiles_find_colliding tiles_below, (player.rect.merge y: player.next_rect.y)
      if collision
        player.y  = collision.rect.y + state.tile_size
        player.dy = 0
        player.action = :standing
      else
        player.action = :falling
      end
    end
  
    def calc_left
      return unless player.dx < 0 && player_next_dx < 0
      tiles_left = tiles_find { |t| t.rect.right <= player.prev_rect.left }
      collision = tiles_find_colliding tiles_left, (player.rect.merge x: player.next_rect.x)
      return unless collision
      player.x  = collision.rect.right
      player.dx = 0
    end
  
    def calc_right
      return unless player.dx > 0 && player_next_dx > 0
      tiles_right = tiles_find { |t| t.rect.left >= player.prev_rect.right }
      collision = tiles_find_colliding tiles_right, (player.rect.merge x: player.next_rect.x)
      return unless collision
      player.x  = collision.rect.left - player.rect.w
      player.dx = 0
    end
  
    def calc_above
      return unless player.dy > 0
      tiles_above = tiles_find { |t| t.rect.y >= player.prev_rect.y }
      collision = tiles_find_colliding tiles_above, (player.rect.merge y: player.next_rect.y)
      return unless collision
      player.dy = 0
      player.y  = collision.rect.bottom - player.rect.h
    end
  
    def player_current_rect
      { x: player.x, y: player.y, w: player.size, h: player.size }
    end
  
    def available_brick_locations
      (0..19).to_a
        .product(0..11)
        .map do |(ordinal_x, ordinal_y)|
        { ordinal_x: ordinal_x,
          ordinal_y: ordinal_y,
          x: ordinal_x * 64,
          y: ordinal_y * 64,
          w: 64,
          h: 64 }
      end
    end
  
    def player
      state.player ||= args.state.new_entity :player
    end
  
    def player_next_dy
      player.dy + state.gravity + state.drag ** 2 * -1
    end
  
    def player_next_dx
      player.dx * 0.8
    end
  
    def player_next_rect
      player.rect.merge x: player.x + player_next_dx,
                        y: player.y + player_next_dy
    end
  
    def player_prev_rect
      player.rect.merge x: player.x - player.dx,
                        y: player.y - player.dy
    end
  
    def player_jump
      return if player.action != :standing
      player.action = :jumping
      player.dy = state.player.jump_power
      current_frame = state.tick_count
      player.action_at = current_frame
    end
  
    def player_jump_increase_air_time
      return if player.action != :jumping
      return if player.action_at.elapsed_time >= player.jump_air_time
      player.dy += player.jump_increase_power
    end
  
    def tiles
      state.tiles
    end
  
    def tiles_find_colliding tiles, target
      tiles.find { |t| t.rect.intersect_rect? target }
    end
  
    def tiles_find &block
      tiles.find_all(&block)
    end
  end
  
  def tick args
    $game ||= Game.new
    $game.args = args
    $game.tick
  end
  
  $gtk.reset

#+end_src

*** Platformer - Clepto Frog - main.rb
#+begin_src ruby
  # ./samples/99_genre_platformer/clepto_frog/app/main.rb
  MAP_FILE_PATH = 'map.txt'
  
  require 'app/map.rb'
  
  class CleptoFrog
    attr_gtk
  
    def render_ending
      state.game_over_at ||= state.tick_count
  
      outputs.labels << [640, 700, "Clepto Frog", 4, 1]
  
      if state.tick_count >= (state.game_over_at + 120)
        outputs.labels << [640, 620, "\"I... I.... don't believe it.\" - New Guy",
                           4, 1, 0, 0, 0, 255 * (state.game_over_at + 120).ease(60)]
      end
  
      if state.tick_count >= (state.game_over_at + 240)
        outputs.labels << [640, 580, "\"He actually stole all the mugs?\" - New Guy",
                           4, 1, 0, 0, 0, 255 * (state.game_over_at + 240).ease(60)]
      end
  
      if state.tick_count >= (state.game_over_at + 360)
        outputs.labels << [640, 540, "\"Kind of feel bad STARTING HIM WITH NOTHING again.\" - New Guy",
                           4, 1, 0, 0, 0, 255 * (state.game_over_at + 360).ease(60)]
      end
  
      outputs.sprites << [640 - 50, 360 - 50, 100, 100,
                          "sprites/square-green.png"]
  
      outputs.labels << [640, 300, "Current Time: #{"%.2f" % state.stuff_time}", 4, 1]
      outputs.labels << [640, 270, "Best Time: #{"%.2f" % state.stuff_best_time}", 4, 1]
  
      if state.tick_count >= (state.game_over_at + 550)
        restart_game
      end
    end
  
    def restart_game
      state.world = nil
      state.x = nil
      state.y = nil
      state.dx = nil
      state.dy = nil
      state.stuff_score = 0
      state.stuff_time = 0
      state.intro_tick_count = nil
      defaults
      state.game_start_at = state.tick_count
      state.scene = :game
      state.game_over_at = nil
    end
  
    def render_intro
      outputs.labels << [640, 700, "Clepto Frog", 4, 1]
      if state.tick_count == 120
        state.scene = :game
        state.game_start_at = state.tick_count
      end
    end
  
    def tick
      defaults
      if state.scene == :intro && state.tick_count <= 120
        render_intro
      elsif state.scene == :ending
        render_ending
      else
        render
      end
      calc
      process_inputs
    end
  
    def defaults
      state.scene ||= :intro
      state.stuff_score     ||= 0
      state.stuff_time      ||= 0
      state.stuff_best_time ||= nil
      state.camera_x ||= 0
      state.camera_y ||= 0
      state.target_camera_scale ||= 1
      state.camera_scale ||= 1
      state.tongue_length          ||= 100
      state.dev_action             ||= :collision_mode
      state.action                 ||= :aiming
      state.tongue_angle           ||= 90
      state.tile_size                = 64
      state.gravity                  = -0.1
      state.air                      = -0.01
      state.player_width             = 60
      state.player_height            = 60
      state.collision_tolerance      = 0.0
      state.previous_tile_size     ||= state.tile_size
      state.x                      ||= 2400
      state.y                      ||= 200
      state.dy                     ||= 0
      state.dx                     ||= 0
      attempt_load_world_from_file
      state.world_lookup           ||= { }
      state.world_collision_rects  ||= []
      state.mode                   ||= :creating
      state.select_menu            ||= [0, 720, 1280, 720]
      state.sprite_quantity        ||= 20
      state.sprite_coords          ||= []
      state.banner_coords          ||= [640, 680 + 720]
      state.sprite_selected        ||= 1
      state.map_saved_at           ||= 0
      state.intro_tick_count       ||= state.tick_count
      if state.sprite_coords == []
        count = 1
        temp_x = 165
        temp_y = 500 + 720
        state.sprite_quantity.times do
          state.sprite_coords += [[temp_x, temp_y, count]]
          temp_x += 100
          count += 1
          if temp_x > 1280 - (165 + 50)
            temp_x = 165
            temp_y -= 75
          end
        end
      end
    end
  
    def start_of_tongue x = nil, y = nil
      x ||= state.x
      y ||= state.y
      [
        x + state.player_width.half,
        y + state.player_height.half
      ]
    end
  
    def stage_definition
      outputs.sprites << [vx(0), vy(0), vw(10000), vw(5875), 'sprites/level-map.png']
    end
  
    def render
      stage_definition
      start_of_tongue_render = [vx(start_of_tongue.x), vy(start_of_tongue.y)]
      end_of_tongue_render = [vx(end_of_tongue.x), vy(end_of_tongue.y)]
  
      if state.anchor_point
        anchor_point_render = [vx(state.anchor_point.x), vy(state.anchor_point.y)]
        outputs.sprites << { x: start_of_tongue_render.x,
                             y: start_of_tongue_render.y,
                             w: vw(2),
                             h: args.geometry.distance(start_of_tongue_render, anchor_point_render),
                             path:  'sprites/square-pink.png',
                             angle_anchor_y: 0,
                             angle: state.tongue_angle - 90 }
      else
        outputs.sprites << { x: vx(start_of_tongue.x),
                             y: vy(start_of_tongue.y),
                             w: vw(2),
                             h: vh(state.tongue_length),
                             path:  'sprites/square-pink.png',
                             angle_anchor_y: 0,
                             angle: state.tongue_angle - 90 }
      end
  
      outputs.sprites << state.objects.map { |o| [vx(o.x), vy(o.y), vw(o.w), vh(o.h), o.path] }
  
      if state.god_mode
        # SHOW HIDE COLLISIONS
        outputs.sprites << state.world.map do |rect|
          x = vx(rect.x)
          y = vy(rect.y)
          if x > -80 && x < 1280 && y > -80 && y < 720
            {
              x: x,
              y: y,
              w: vw(rect.w || state.tile_size),
              h: vh(rect.h || state.tile_size),
              path: 'sprites/square-gray.png',
              a: 128
            }
          end
        end
      end
  
      render_player
      outputs.sprites << [vx(2315), vy(45), vw(569), vh(402), 'sprites/square-blue.png', 0, 40]
  
      # Label in top left of the screen
      outputs.primitives << [20, 640, 180, 70, 255, 255, 255, 128].solid
      outputs.primitives << [30, 700, "Stuff: #{state.stuff_score} of #{$mugs.count}", 1].label
      outputs.primitives << [30, 670, "Time: #{"%.2f" % state.stuff_time}", 1].label
  
      if state.god_mode
        if state.map_saved_at > 0 && state.map_saved_at.elapsed_time < 120
          outputs.primitives << [920, 670, 'Map has been exported!', 1, 0, 50, 100, 50].label
        end
  
  
        # Creates sprite following mouse to help indicate which sprite you have selected
        outputs.primitives << [inputs.mouse.position.x - 32 * state.camera_scale,
                               inputs.mouse.position.y - 32 * state.camera_scale,
                               state.tile_size * state.camera_scale,
                               state.tile_size * state.camera_scale, 'sprites/square-indigo.png', 0, 100].sprite
      end
  
      render_mini_map
      outputs.primitives << [0, 0, 1280, 720, 255, 255, 255, 255 * state.game_start_at.ease(60, :flip)].solid
    end
  
    def render_mini_map
      x, y = 1170, 10
      outputs.primitives << [x, y, 100, 58, 0, 0, 0, 200].solid
      outputs.primitives << [x + args.state.x.fdiv(100) - 1, y + args.state.y.fdiv(100) - 1, 2, 2, 0, 255, 0].solid
      t_start = start_of_tongue
      t_end = end_of_tongue
      outputs.primitives << [
        x + t_start.x.fdiv(100), y + t_start.y.fdiv(100),
        x + t_end.x.fdiv(100), y + t_end.y.fdiv(100),
        255, 255, 255
      ].line
  
      state.objects.each do |o|
        outputs.primitives << [x + o.x.fdiv(100) - 1, y + o.y.fdiv(100) - 1, 2, 2, 200, 200, 0].solid
      end
    end
  
    def calc_camera percentage_override = nil
      percentage = percentage_override || (0.2 * state.camera_scale)
      target_scale = state.target_camera_scale
      distance_scale = target_scale - state.camera_scale
      state.camera_scale += distance_scale * percentage
  
      target_x = state.x * state.target_camera_scale
      target_y = state.y * state.target_camera_scale
  
      distance_x = target_x - (state.camera_x + 640)
      distance_y = target_y - (state.camera_y + 360)
      state.camera_x += distance_x * percentage if distance_x.abs > 1
      state.camera_y += distance_y * percentage if distance_y.abs > 1
      state.camera_x = 0 if state.camera_x < 0
      state.camera_y = 0 if state.camera_y < 0
    end
  
    def vx x
       (x * state.camera_scale) - state.camera_x
    end
  
    def vy y
      (y * state.camera_scale) - state.camera_y
    end
  
    def vw w
      w * state.camera_scale
    end
  
    def vh h
      h * state.camera_scale
    end
  
    def calc
      calc_camera
      calc_world_lookup
      calc_player
      calc_on_floor
      calc_score
    end
  
    def set_camera_scale v = nil
      return if v < 0.1
      state.target_camera_scale = v
    end
  
    def process_inputs_god_mode
      return unless state.god_mode
  
      if inputs.keyboard.key_down.equal_sign || (inputs.keyboard.equal_sign && state.tick_count.mod_zero?(10))
        set_camera_scale state.camera_scale + 0.1
      elsif inputs.keyboard.key_down.hyphen || (inputs.keyboard.hyphen && state.tick_count.mod_zero?(10))
        set_camera_scale state.camera_scale - 0.1
      elsif inputs.keyboard.eight || inputs.keyboard.zero
        set_camera_scale 1
      end
  
      if inputs.mouse.click
        state.id_seed += 1
        id = state.id_seed
        x = state.camera_x + (inputs.mouse.click.x.fdiv(state.camera_scale) - 32)
        y = state.camera_y + (inputs.mouse.click.y.fdiv(state.camera_scale) - 32)
        x = ((x + 2).idiv 4) * 4
        y = ((y + 2).idiv 4) * 4
        w = 64
        h = 64
        candidate_rect = { id: id, x: x, y: y, w: w, h: h }
        scaled_candidate_rect = { x: x + 30, y: y + 30, w: w - 60, h: h - 60 }
        to_remove = state.world.find { |r| r.intersect_rect? scaled_candidate_rect }
        if to_remove && args.inputs.keyboard.x
          state.world.reject! { |r| r.id == to_remove.id }
        else
          state.world << candidate_rect
        end
        export_map
        state.world_lookup = {}
        state.world_collision_rects = nil
        calc_world_lookup
      end
  
      if input_up?
        state.y += 10
        state.dy = 0
      elsif input_down?
        state.y -= 10
        state.dy = 0
      end
  
      if input_left?
        state.x -= 10
        state.dx = 0
      elsif input_right?
        state.x += 10
        state.dx = 0
      end
    end
  
    def process_inputs
      if state.scene == :game
        process_inputs_player_movement
        process_inputs_god_mode
      end
    end
  
    def input_up?
      inputs.keyboard.w || inputs.keyboard.up || inputs.keyboard.k
    end
  
    def input_up_released?
      inputs.keyboard.key_up.w ||
      inputs.keyboard.key_up.up ||
      inputs.keyboard.key_up.k
    end
  
    def input_down?
      inputs.keyboard.s || inputs.keyboard.down || inputs.keyboard.j
    end
  
    def input_down_released?
      inputs.keyboard.key_up.s ||
      inputs.keyboard.key_up.down ||
      inputs.keyboard.key_up.j
    end
  
    def input_left?
      inputs.keyboard.a || inputs.keyboard.left || inputs.keyboard.h
    end
  
    def input_right?
      inputs.keyboard.d || inputs.keyboard.right || inputs.keyboard.l
    end
  
    def set_object path, w, h
      state.object = path
      state.object_w = w
      state.object_h = h
    end
  
    def collision_mode
      state.dev_action = :collision_mode
    end
  
    def process_inputs_player_movement
      if inputs.keyboard.key_down.g
        state.god_mode = !state.god_mode
        puts state.god_mode
      end
  
      if inputs.keyboard.key_down.u && state.dev_action == :collision_mode
        state.world = state.world[0..-2]
        state.world_lookup = {}
      end
  
      if inputs.keyboard.key_down.space && !state.anchor_point
        state.tongue_length = 0
        state.action = :shooting
        outputs.sounds << 'sounds/shooting.wav'
      elsif inputs.keyboard.key_down.space
        state.action = :aiming
        state.anchor_point  = nil
        state.tongue_length = 100
      end
  
      if state.anchor_point
        if input_up?
          if state.tongue_length >= 105
            state.tongue_length -= 5
            state.dy += 0.8
          end
        elsif input_down?
          state.tongue_length += 5
          state.dy -= 0.8
        end
  
        if input_left? && state.dx > 1
          state.dx *= 0.98
        elsif input_left? && state.dx < -1
          state.dx *= 1.03
        elsif input_left? && !state.on_floor
          state.dx -= 3
        elsif input_right? && state.dx > 1
          state.dx *= 1.03
        elsif input_right? && state.dx < -1
          state.dx *= 0.98
        elsif input_right? && !state.on_floor
          state.dx += 3
        end
      else
        if input_left?
          state.tongue_angle += 1.5
          state.tongue_angle = state.tongue_angle
        elsif input_right?
          state.tongue_angle -= 1.5
          state.tongue_angle = state.tongue_angle
        end
      end
    end
  
    def attempt_load_world_from_file
      return if state.world
      # exported_world = gtk.read_file(MAP_FILE_PATH)
      state.world = []
      state.objects = []
  
      if $collisions
        state.id_seed ||= 0
        $collisions.each do |x, y, w, h|
          state.id_seed += 1
          state.world << { id: state.id_seed, x: x, y: y, w: w, h: h }
        end
      end
  
      if $mugs
        $mugs.map do |x, y, w, h, path|
          state.objects << [x, y, w, h, path]
        end
      end
    end
  
    def calc_world_lookup
      if state.tile_size != state.previous_tile_size
        state.previous_tile_size = state.tile_size
        state.world_lookup = {}
      end
  
      return if state.world_lookup.keys.length > 0
      return unless state.world.length > 0
  
      # Searches through the world and finds the cordinates that exist
      state.world_lookup = {}
      state.world.each do |rect|
        state.world_lookup[rect.id] = rect
      end
  
      # Assigns collision rects for every sprite drawn
      state.world_collision_rects =
        state.world_lookup
             .keys
             .map do |key|
               rect = state.world_lookup[key]
               s = state.tile_size
               rect.w ||= s
               rect.h ||= s
               {
                 args:       rect,
                 left_right: { x: rect.x,     y: rect.y + 4, w: rect.w,     h: rect.h - 6 },
                 top:        { x: rect.x + 4, y: rect.y + 6, w: rect.w - 8, h: rect.h - 6 },
                 bottom:     { x: rect.x + 1, y: rect.y - 1, w: rect.w - 2, h: rect.h - 8 },
               }
             end
  
    end
  
    def calc_pendulum
      return if !state.anchor_point
      target_x = state.anchor_point.x - start_of_tongue.x
      target_y = state.anchor_point.y -
                 state.tongue_length - 5 - 20 - state.player_height
  
      diff_y = state.y - target_y
  
      if target_x > 0
        state.dx += 0.6
      elsif target_x < 0
        state.dx -= 0.6
      end
  
      if diff_y > 0
        state.dy -= 0.1
      elsif diff_y < 0
        state.dy += 0.1
      end
  
      state.dx *= 0.99
  
      if state.dy.abs < 2
        state.dy *= 0.8
      else
        state.dy *= 0.90
      end
  
      if state.tongue_length && state.y
        state.dy += state.tongue_angle.vector_y state.tongue_length.fdiv(1000)
      end
    end
  
    def calc_tongue_angle
      return unless state.anchor_point
      state.tongue_angle = args.geometry.angle_from state.anchor_point, start_of_tongue
      state.tongue_length = args.geometry.distance(start_of_tongue, state.anchor_point)
      state.tongue_length = state.tongue_length.greater(100)
    end
  
    def player_from_end_of_tongue
      p = state.tongue_angle.vector(state.tongue_length)
      derived_start = [state.anchor_point.x - p.x, state.anchor_point.y - p.y]
      derived_start.x -= state.player_width.half
      derived_start.y -= state.player_height.half
      derived_start
    end
  
    def end_of_tongue
      p = state.tongue_angle.vector(state.tongue_length)
      { x: start_of_tongue.x + p.x, y: start_of_tongue.y + p.y }
    end
  
    def calc_shooting
      calc_shooting_increment
      calc_shooting_increment
      calc_shooting_increment
      calc_shooting_increment
      calc_shooting_increment
      calc_shooting_increment
    end
  
    def calc_shooting_increment
      return unless state.action == :shooting
      state.tongue_length += 5
      potential_anchor = end_of_tongue
      if potential_anchor.x <= 0
        state.anchor_point = potential_anchor
        state.action = :anchored
        outputs.sounds << 'sounds/attached.wav'
      elsif potential_anchor.x >= 10000
        state.anchor_point = potential_anchor
        state.action = :anchored
        outputs.sounds << 'sounds/attached.wav'
      elsif potential_anchor.y <= 0
        state.anchor_point = potential_anchor
        state.action = :anchored
        outputs.sounds << 'sounds/attached.wav'
      elsif potential_anchor.y >= 5875
        state.anchor_point = potential_anchor
        state.action = :anchored
        outputs.sounds << 'sounds/attached.wav'
      else
        anchor_rect = { x: potential_anchor.x - 5, y: potential_anchor.y - 5, w: 10, h: 10 }
        collision = state.world_collision_rects.find_all do |v|
          v[:args].intersect_rect?(anchor_rect)
        end.first
        if collision
          state.anchor_point = potential_anchor
          state.action = :anchored
        outputs.sounds << 'sounds/attached.wav'
        end
      end
    end
  
    def calc_player
      calc_shooting
      if !state.god_mode
        state.dy += state.gravity  # Since acceleration is the change in velocity, the change in y (dy) increases every frame
        state.dx += state.dx * state.air
      end
      calc_pendulum
      calc_box_collision
      calc_edge_collision
      if !state.god_mode
        state.y  += state.dy
        state.x  += state.dx
      end
      calc_tongue_angle
    end
  
    def calc_box_collision
      return unless state.world_lookup.keys.length > 0
      collision_floor
      collision_left
      collision_right
      collision_ceiling
    end
  
    def calc_edge_collision
      # Ensures that player doesn't fall below the map
      if next_y < 0 && state.dy < 0
        state.y = 0
        state.dy = state.dy.abs * 0.8
        state.collision_on_y = true
      # Ensures player doesn't go insanely high
      elsif next_y > 5875 - state.tile_size && state.dy > 0
        state.y = 5875 - state.tile_size
        state.dy = state.dy.abs * 0.8 * -1
        state.collision_on_y = true
      end
  
      # Ensures that player remains in the horizontal range its supposed to
      if state.x >= 10000 - state.tile_size && state.dx > 0
        state.x = 10000 - state.tile_size
        state.dx = state.dx.abs * 0.8 * -1
        state.collision_on_x = true
      elsif state.x <= 0 && state.dx < 0
        state.x = 0
        state.dx = state.dx.abs * 0.8
        state.collision_on_x = true
      end
    end
  
    def next_y
      state.y + state.dy
    end
  
    def next_x
      if state.dx < 0
        return (state.x + state.dx) - (state.tile_size - state.player_width)
      else
        return (state.x + state.dx) + (state.tile_size - state.player_width)
      end
    end
  
    def collision_floor
      return unless state.dy <= 0
  
      player_rect = [state.x, next_y, state.tile_size, state.tile_size]
  
      # Runs through all the sprites on the field and determines if the player hits the bottom of sprite (hence "-0.1" above)
      floor_collisions = state.world_collision_rects
                           .find_all { |r| r[:top].intersect_rect?(player_rect, state.collision_tolerance) }
                           .first
  
      return unless floor_collisions
      state.y = floor_collisions[:top].top
      state.dy = state.dy.abs * 0.8
    end
  
    def collision_left
      return unless state.dx < 0
      player_rect = [next_x, state.y, state.tile_size, state.tile_size]
  
      # Runs through all the sprites on the field and determines if the player hits the left side of sprite (hence "-0.1" above)
      left_side_collisions = state.world_collision_rects
                               .find_all { |r| r[:left_right].intersect_rect?(player_rect, state.collision_tolerance) }
                               .first
  
      return unless left_side_collisions
      state.x = left_side_collisions[:left_right].right + 1
      state.dx = state.dy.abs * 0.8
      state.collision_on_x = true
    end
  
    def collision_right
      return unless state.dx > 0
  
      player_rect = [next_x, state.y, state.tile_size, state.tile_size]
      # Runs through all the sprites on the field and determines if the player hits the right side of sprite (hence "-0.1" above)
      right_side_collisions = state.world_collision_rects
                                .find_all { |r| r[:left_right].intersect_rect?(player_rect, state.collision_tolerance) }
                                .first
  
      return unless right_side_collisions
      state.x = right_side_collisions[:left_right].left - state.tile_size - 1
      state.dx = state.dx.abs * 0.8 * -1
      state.collision_on_x = true
    end
  
    def collision_ceiling
      return unless state.dy > 0
  
      player_rect = [state.x, next_y, state.player_width, state.player_height]
  
      # Runs through all the sprites on the field and determines if the player hits the ceiling of sprite (hence "+0.1" above)
      ceil_collisions = state.world_collision_rects
                          .find_all { |r| r[:bottom].intersect_rect?(player_rect, state.collision_tolerance) }
                          .first
  
      return unless ceil_collisions
      state.y = ceil_collisions[:bottom].y - state.tile_size - 1
      state.dy = state.dy.abs * 0.8 * -1
      state.collision_on_y = true
    end
  
    def to_coord point
      # Integer divides (idiv) point.x to turn into grid
      # Then, you can just multiply each integer by state.tile_size
      # later and huzzah. Grid coordinates
      [point.x.idiv(state.tile_size), point.y.idiv(state.tile_size)]
    end
  
    def export_map
      export_string = "$collisions = [\n"
      export_string += state.world.map do |rect|
        "[#{rect.x},#{rect.y},#{rect.w},#{rect.h}],"
      end.join "\n"
      export_string += "\n]\n\n"
      export_string += "$mugs = [\n"
      export_string += state.objects.map do |x, y, w, h, path|
        "[#{x},#{y},#{w},#{h},'#{path}'],"
      end.join "\n"
      export_string += "\n]\n\n"
      gtk.write_file(MAP_FILE_PATH, export_string)
      state.map_saved_at = state.tick_count
    end
  
    def inputs_export_stage
    end
  
    def calc_score
      return unless state.scene == :game
      player = [state.x, state.y, state.player_width, state.player_height]
      collected = state.objects.find_all { |s| s.intersect_rect? player }
      state.stuff_score += collected.length
      if collected.length > 0
        outputs.sounds << 'sounds/collectable.wav'
      end
      state.objects = state.objects.reject { |s| collected.include? s }
      state.stuff_time += 0.01
      if state.objects.length == 0
        if !state.stuff_best_time || state.stuff_time < state.stuff_best_time
          state.stuff_best_time = state.stuff_time
        end
        state.game_over_at = nil
        state.scene = :ending
      end
    end
  
    def calc_on_floor
      if state.action == :anchored
        state.on_floor = false
        state.on_floor_debounce = 30
      else
        state.on_floor_debounce ||= 30
  
        if state.dy.round != 0
          state.on_floor_debounce = 30
          state.on_floor = false
        else
          state.on_floor_debounce -= 1
        end
  
        if state.on_floor_debounce <= 0
          state.on_floor_debounce = 0
          state.on_floor = true
        end
      end
    end
  
    def render_player
      path = "sprites/square-green.png"
      angle = 0
      # outputs.labels << [vx(state.x), vy(state.y) - 30, "dy: #{state.dy.round}"]
      if state.action == :idle
        # outputs.labels << [vx(state.x), vy(state.y), "IDLE"]
        path = "sprites/square-green.png"
      elsif state.action == :aiming && !state.on_floor
        # outputs.labels << [vx(state.x), vy(state.y), "AIMING AIR BORN"]
        angle = state.tongue_angle - 90
        path = "sprites/square-green.png"
      elsif state.action == :aiming # ON THE GROUND
        # outputs.labels << [vx(state.x), vy(state.y), "AIMING GROUND"]
        path = "sprites/square-green.png"
      elsif state.action == :shooting && !state.on_floor
        # outputs.labels << [vx(state.x), vy(state.y), "SHOOTING AIR BORN"]
        path = "sprites/square-green.png"
        angle = state.tongue_angle - 90
      elsif state.action == :shooting
        # outputs.labels << [vx(state.x), vy(state.y), "SHOOTING ON GROUND"]
        path = "sprites/square-green.png"
      elsif state.action == :anchored
        # outputs.labels << [vx(state.x), vy(state.y), "SWINGING"]
        angle = state.tongue_angle - 90
        path = "sprites/square-green.png"
      end
  
      outputs.sprites << [vx(state.x),
                          vy(state.y),
                          vw(state.player_width),
                          vh(state.player_height),
                          path,
                          angle]
    end
  
    def render_player_old
      # Player
      if state.action == :aiming
        path = 'sprites\frg\idle\frog_idle.png'
        if state.dx > 2
  	  #directional right sprite was here but i needa redo it
          path = 'sprites\frg\anchor\frog-anchor-0.png'
        #directional left sprite was here but i needa redo it
  	  elsif state.dx < -2
          path = 'sprites\frg\anchor\frog-anchor-0.png'
        end
        outputs.sprites << [vx(state.x),
                            vy(state.y),
                            vw(state.player_width),
                            vh(state.player_height),
                            path,
                            (state.tongue_angle - 90)]
      elsif state.action == :anchored || state.action == :shooting
        outputs.sprites << [vx(state.x),
                            vy(state.y),
                            vw(state.player_width),
                            vw(state.player_height),
                            'sprites/animations_povfrog/frog_bwah_up.png',
                            (state.tongue_angle - 90)]
      end
    end
  end
  
  
  $game = CleptoFrog.new
  
  def tick args
    if args.state.scene == :game
      tick_instructions args, "SPACE to SHOOT and RELEASE tongue. LEFT, RIGHT to SWING and BUILD momentum. MINIMAP in bottom right corner.", 360
    end
    $game.args = args
    $game.tick
  end
  
  def tick_instructions args, text, y = 715
    return if args.state.key_event_occurred
    if args.inputs.keyboard.directional_vector || args.inputs.keyboard.key_down.space
      args.state.key_event_occurred = true
    end
  
    args.outputs.debug << [0, y - 50, 1280, 60].solid
    args.outputs.debug << [640, y, text, 1, 1, 255, 255, 255].label
    args.outputs.debug << [640, y - 25, "(SPACE to dismiss instructions)" , -2, 1, 255, 255, 255].label
  end

#+end_src

*** Platformer - Clepto Frog - map.rb
#+begin_src ruby
  # ./samples/99_genre_platformer/clepto_frog/app/map.rb
  $collisions = [
    [326, 463, 64, 64],
    [274, 462, 64, 64],
    [326, 413, 64, 64],
    [275, 412, 64, 64],
    [124, 651, 64, 64],
    [72, 651, 64, 64],
    [124, 600, 64, 64],
    [69, 599, 64, 64],
    [501, 997, 64, 64],
    [476, 995, 64, 64],
    [3224, 2057, 64, 64],
    [3224, 1994, 64, 64],
    [3225, 1932, 64, 64],
    [3225, 1870, 64, 64],
    [3226, 1806, 64, 64],
    [3224, 1744, 64, 64],
    [3225, 1689, 64, 64],
    [3226, 1660, 64, 64],
    [3161, 1658, 64, 64],
    [3097, 1660, 64, 64],
    [3033, 1658, 64, 64],
    [2969, 1658, 64, 64],
    [2904, 1658, 64, 64],
    [2839, 1657, 64, 64],
    [2773, 1657, 64, 64],
    [2709, 1658, 64, 64],
    [2643, 1657, 64, 64],
    [2577, 1657, 64, 64],
    [2509, 1658, 64, 64],
    [2440, 1658, 64, 64],
    [2371, 1658, 64, 64],
    [2301, 1659, 64, 64],
    [2230, 1659, 64, 64],
    [2159, 1659, 64, 64],
    [2092, 1660, 64, 64],
    [2025, 1661, 64, 64],
    [1958, 1660, 64, 64],
    [1888, 1659, 64, 64],
    [1817, 1657, 64, 64],
    [1745, 1656, 64, 64],
    [1673, 1658, 64, 64],
    [1605, 1660, 64, 64],
    [1536, 1658, 64, 64],
    [1465, 1660, 64, 64],
    [1386, 1960, 64, 64],
    [1384, 1908, 64, 64],
    [1387, 1862, 64, 64],
    [1326, 1863, 64, 64],
    [1302, 1862, 64, 64],
    [1119, 1906, 64, 64],
    [1057, 1905, 64, 64],
    [994, 1905, 64, 64],
    [937, 1904, 64, 64],
    [896, 1904, 64, 64],
    [1001, 1845, 64, 64],
    [1003, 1780, 64, 64],
    [1003, 1718, 64, 64],
    [692, 1958, 64, 64],
    [691, 1900, 64, 64],
    [774, 1861, 64, 64],
    [712, 1861, 64, 64],
    [691, 1863, 64, 64],
    [325, 2133, 64, 64],
    [275, 2134, 64, 64],
    [326, 2082, 64, 64],
    [275, 2082, 64, 64],
    [124, 2321, 64, 64],
    [71, 2320, 64, 64],
    [123, 2267, 64, 64],
    [71, 2268, 64, 64],
    [2354, 1859, 64, 64],
    [2292, 1859, 64, 64],
    [2231, 1857, 64, 64],
    [2198, 1858, 64, 64],
    [2353, 1802, 64, 64],
    [2296, 1798, 64, 64],
    [2233, 1797, 64, 64],
    [2200, 1797, 64, 64],
    [2352, 1742, 64, 64],
    [2288, 1741, 64, 64],
    [2230, 1743, 64, 64],
    [2196, 1743, 64, 64],
    [1736, 460, 64, 64],
    [1735, 400, 64, 64],
    [1736, 339, 64, 64],
    [1736, 275, 64, 64],
    [1738, 210, 64, 64],
    [1735, 145, 64, 64],
    [1735, 87, 64, 64],
    [1736, 51, 64, 64],
    [539, 289, 64, 64],
    [541, 228, 64, 64],
    [626, 191, 64, 64],
    [572, 192, 64, 64],
    [540, 193, 64, 64],
    [965, 233, 64, 64],
    [904, 234, 64, 64],
    [840, 234, 64, 64],
    [779, 234, 64, 64],
    [745, 236, 64, 64],
    [851, 169, 64, 64],
    [849, 108, 64, 64],
    [852, 50, 64, 64],
    [1237, 289, 64, 64],
    [1236, 228, 64, 64],
    [1238, 197, 64, 64],
    [1181, 192, 64, 64],
    [1152, 192, 64, 64],
    [1443, 605, 64, 64],
    [1419, 606, 64, 64],
    [1069, 925, 64, 64],
    [1068, 902, 64, 64],
    [1024, 927, 64, 64],
    [1017, 897, 64, 64],
    [963, 926, 64, 64],
    [958, 898, 64, 64],
    [911, 928, 64, 64],
    [911, 896, 64, 64],
    [2132, 803, 64, 64],
    [2081, 803, 64, 64],
    [2131, 752, 64, 64],
    [2077, 751, 64, 64],
    [2615, 649, 64, 64],
    [2564, 651, 64, 64],
    [2533, 650, 64, 64],
    [2027, 156, 64, 64],
    [1968, 155, 64, 64],
    [1907, 153, 64, 64],
    [1873, 155, 64, 64],
    [2025, 95, 64, 64],
    [1953, 98, 64, 64],
    [1894, 100, 64, 64],
    [1870, 100, 64, 64],
    [2029, 45, 64, 64],
    [1971, 48, 64, 64],
    [1915, 47, 64, 64],
    [1873, 47, 64, 64],
    [3956, 288, 64, 64],
    [3954, 234, 64, 64],
    [4042, 190, 64, 64],
    [3990, 190, 64, 64],
    [3958, 195, 64, 64],
    [3422, 709, 64, 64],
    [3425, 686, 64, 64],
    [3368, 709, 64, 64],
    [3364, 683, 64, 64],
    [3312, 711, 64, 64],
    [3307, 684, 64, 64],
    [3266, 712, 64, 64],
    [3269, 681, 64, 64],
    [4384, 236, 64, 64],
    [4320, 234, 64, 64],
    [4257, 235, 64, 64],
    [4192, 234, 64, 64],
    [4162, 234, 64, 64],
    [4269, 171, 64, 64],
    [4267, 111, 64, 64],
    [4266, 52, 64, 64],
    [4580, 458, 64, 64],
    [4582, 396, 64, 64],
    [4582, 335, 64, 64],
    [4581, 275, 64, 64],
    [4581, 215, 64, 64],
    [4581, 152, 64, 64],
    [4582, 89, 64, 64],
    [4583, 51, 64, 64],
    [4810, 289, 64, 64],
    [4810, 227, 64, 64],
    [4895, 189, 64, 64],
    [4844, 191, 64, 64],
    [4809, 191, 64, 64],
    [5235, 233, 64, 64],
    [5176, 232, 64, 64],
    [5118, 230, 64, 64],
    [5060, 232, 64, 64],
    [5015, 237, 64, 64],
    [5123, 171, 64, 64],
    [5123, 114, 64, 64],
    [5121, 51, 64, 64],
    [5523, 461, 64, 64],
    [5123, 42, 64, 64],
    [5525, 401, 64, 64],
    [5525, 340, 64, 64],
    [5526, 273, 64, 64],
    [5527, 211, 64, 64],
    [5525, 150, 64, 64],
    [5527, 84, 64, 64],
    [5524, 44, 64, 64],
    [5861, 288, 64, 64],
    [5861, 229, 64, 64],
    [5945, 193, 64, 64],
    [5904, 193, 64, 64],
    [5856, 194, 64, 64],
    [6542, 234, 64, 64],
    [6478, 235, 64, 64],
    [6413, 238, 64, 64],
    [6348, 235, 64, 64],
    [6285, 236, 64, 64],
    [6222, 235, 64, 64],
    [6160, 235, 64, 64],
    [6097, 236, 64, 64],
    [6069, 237, 64, 64],
    [6321, 174, 64, 64],
    [6318, 111, 64, 64],
    [6320, 49, 64, 64],
    [6753, 291, 64, 64],
    [6752, 227, 64, 64],
    [6753, 192, 64, 64],
    [6692, 191, 64, 64],
    [6668, 193, 64, 64],
    [6336, 604, 64, 64],
    [6309, 603, 64, 64],
    [7264, 461, 64, 64],
    [7264, 395, 64, 64],
    [7264, 333, 64, 64],
    [7264, 270, 64, 64],
    [7265, 207, 64, 64],
    [7266, 138, 64, 64],
    [7264, 78, 64, 64],
    [7266, 48, 64, 64],
    [7582, 149, 64, 64],
    [7524, 147, 64, 64],
    [7461, 146, 64, 64],
    [7425, 148, 64, 64],
    [7580, 86, 64, 64],
    [7582, 41, 64, 64],
    [7519, 41, 64, 64],
    [7460, 40, 64, 64],
    [7427, 96, 64, 64],
    [7427, 41, 64, 64],
    [8060, 288, 64, 64],
    [8059, 226, 64, 64],
    [8145, 194, 64, 64],
    [8081, 194, 64, 64],
    [8058, 195, 64, 64],
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    [2390, 2386, 64, 64],
    [2328, 2386, 64, 64],
    [2264, 2386, 64, 64],
    [2200, 2386, 64, 64],
    [2137, 2387, 64, 64],
    [2071, 2385, 64, 64],
    [2016, 2389, 64, 64],
    [2517, 2341, 64, 64],
    [2518, 2316, 64, 64],
    [2456, 2316, 64, 64],
    [2393, 2316, 64, 64],
    [2328, 2317, 64, 64],
    [2264, 2316, 64, 64],
    [2207, 2318, 64, 64],
    [2144, 2317, 64, 64],
    [2081, 2316, 64, 64],
    [2015, 2342, 64, 64],
    [2016, 2315, 64, 64],
    [869, 3709, 64, 64],
    [819, 3710, 64, 64],
    [869, 3658, 64, 64],
    [820, 3658, 64, 64],
    [0, 0, 64, 64],
    [0, 1670, 64, 64],
    [6691, 1653, 64, 64],
    [1521, 3792, 64, 64],
    [0, 5137, 64, 64],
    [3898, 2400, 64, 64],
    [3835, 2400, 64, 64],
    [3771, 2400, 64, 64],
    [3708, 2401, 64, 64],
    [3646, 2401, 64, 64],
    [3587, 2401, 64, 64],
    [3530, 2401, 64, 64],
    [3897, 2340, 64, 64],
    [3897, 2295, 64, 64],
    [3834, 2296, 64, 64],
    [3773, 2295, 64, 64],
    [3710, 2296, 64, 64],
    [3656, 2295, 64, 64],
    [3593, 2294, 64, 64],
    [3527, 2339, 64, 64],
    [3531, 2293, 64, 64],
    [4152, 2903, 64, 64],
    [4155, 2858, 64, 64],
    [3942, 1306, 64, 64],
    [3942, 1279, 64, 64],
    [3879, 1306, 64, 64],
    [3881, 1278, 64, 64],
    [3819, 1305, 64, 64],
    [3819, 1277, 64, 64],
    [3756, 1306, 64, 64],
    [3756, 1277, 64, 64],
    [3694, 1306, 64, 64],
    [3695, 1277, 64, 64],
    [3631, 1306, 64, 64],
    [3632, 1278, 64, 64],
    [3565, 1306, 64, 64],
    [3567, 1279, 64, 64],
    [4432, 1165, 64, 64],
    [4408, 1163, 64, 64],
    [5123, 1003, 64, 64],
    [5065, 1002, 64, 64],
    [5042, 1002, 64, 64],
    [6020, 1780, 64, 64],
    [6020, 1756, 64, 64],
    [5959, 1780, 64, 64],
    [5959, 1752, 64, 64],
    [5897, 1779, 64, 64],
    [5899, 1752, 64, 64],
    [5836, 1779, 64, 64],
    [5836, 1751, 64, 64],
    [5776, 1780, 64, 64],
    [5776, 1754, 64, 64],
    [5717, 1780, 64, 64],
    [5716, 1752, 64, 64],
    [5658, 1781, 64, 64],
    [5658, 1755, 64, 64],
    [5640, 1781, 64, 64],
    [5640, 1754, 64, 64],
    [5832, 2095, 64, 64],
    [5782, 2093, 64, 64],
    [5832, 2044, 64, 64],
    [5777, 2043, 64, 64],
    [4847, 2577, 64, 64],
    [4795, 2577, 64, 64],
    [4846, 2526, 64, 64],
    [4794, 2526, 64, 64],
    [8390, 923, 64, 64],
    [8363, 922, 64, 64],
    [7585, 1084, 64, 64],
    [7582, 1058, 64, 64],
    [7525, 1084, 64, 64],
    [7524, 1056, 64, 64],
    [7478, 1085, 64, 64],
    [7476, 1055, 64, 64],
    [7421, 1086, 64, 64],
    [7421, 1052, 64, 64],
    [7362, 1085, 64, 64],
    [7361, 1053, 64, 64],
    [7307, 1087, 64, 64],
    [7307, 1054, 64, 64],
    [7258, 1086, 64, 64],
    [7255, 1058, 64, 64],
    [7203, 1083, 64, 64],
    [7203, 1055, 64, 64],
    [7161, 1085, 64, 64],
    [7158, 1057, 64, 64],
    [7100, 1083, 64, 64],
    [7099, 1058, 64, 64],
    [7038, 1082, 64, 64],
    [7038, 1058, 64, 64],
    [6982, 1083, 64, 64],
    [6984, 1057, 64, 64],
    [0, 0, 64, 64],
    [0, 1670, 64, 64],
    [6691, 1653, 64, 64],
    [1521, 3792, 64, 64],
    [0, 5137, 64, 64],
    [0, 0, 64, 64],
    [0, 1670, 64, 64],
    [6691, 1653, 64, 64],
    [1521, 3792, 64, 64],
    [0, 5137, 64, 64],
    [0, 0, 64, 64],
    [0, 1670, 64, 64],
    [6691, 1653, 64, 64],
    [1521, 3792, 64, 64],
    [0, 5137, 64, 64],
    [8346, 424, 64, 64],
    [8407, 376, 64, 64],
    [8375, 386, 64, 64],
    [8407, 347, 64, 64],
    [8388, 343, 64, 64],
    [8320, 423, 64, 64],
    [8319, 363, 64, 64],
    [8368, 303, 64, 64],
    [8359, 303, 64, 64],
    [8318, 330, 64, 64],
    [9369, 425, 64, 64],
    [9340, 425, 64, 64],
    [9431, 376, 64, 64],
    [9414, 382, 64, 64],
    [9387, 391, 64, 64],
    [9431, 349, 64, 64],
    [9412, 344, 64, 64],
    [9392, 305, 64, 64],
    [9339, 365, 64, 64],
    [9341, 333, 64, 64],
    [9384, 301, 64, 64],
    [7673, 1896, 64, 64],
    [7642, 1834, 64, 64],
    [7646, 1901, 64, 64],
    [4500, 4054, 64, 64],
    [4476, 4055, 64, 64],
    [4459, 3997, 64, 64],
    [76, 5215, 64, 64],
    [39, 5217, 64, 64],
    [0,       0, 10000, 40],
    [0,    1670, 3250, 60],
    [6691, 1653, 3290, 60],
    [1521, 3792, 7370, 60],
    [0, 5137, 3290, 60]
  ]
  
  $mugs = [
    [85, 87, 39, 43, "sprites/square-orange.png"],
    [958, 1967, 39, 43, "sprites/square-orange.png"],
    [2537, 1734, 39, 43, "sprites/square-orange.png"],
    [3755, 2464, 39, 43, "sprites/square-orange.png"],
    [1548, 3273, 39, 43, "sprites/square-orange.png"],
    [2050, 220, 39, 43, "sprites/square-orange.png"],
    [854, 297, 39, 43, "sprites/square-orange.png"],
    [343, 526, 39, 43, "sprites/square-orange.png"],
    [3454, 772, 39, 43, "sprites/square-orange.png"],
    [5041, 298, 39, 43, "sprites/square-orange.png"],
    [6089, 300, 39, 43, "sprites/square-orange.png"],
    [6518, 295, 39, 43, "sprites/square-orange.png"],
    [7661, 47, 39, 43, "sprites/square-orange.png"],
    [9392, 1125, 39, 43, "sprites/square-orange.png"],
    [7298, 1152, 39, 43, "sprites/square-orange.png"],
    [5816, 1843, 39, 43, "sprites/square-orange.png"],
    [876, 3772, 39, 43, "sprites/square-orange.png"],
    [1029, 4667, 39, 43, "sprites/square-orange.png"],
    [823, 5324, 39, 43, "sprites/square-orange.png"],
    [3251, 5220, 39, 43, "sprites/square-orange.png"],
    [4747, 5282, 39, 43, "sprites/square-orange.png"],
    [9325, 5178, 39, 43, "sprites/square-orange.png"],
    [9635, 4298, 39, 43, "sprites/square-orange.png"],
    [7837, 4127, 39, 43, "sprites/square-orange.png"],
    [8651, 1971, 39, 43, "sprites/square-orange.png"],
    [6892, 2031, 39, 43, "sprites/square-orange.png"],
    [4626, 3882, 39, 43, "sprites/square-orange.png"],
    [4024, 4554, 39, 43, "sprites/square-orange.png"],
    [3925, 3337, 39, 43, "sprites/square-orange.png"],
    [5064, 1064, 39, 43, "sprites/square-orange.png"]
  ]

#+end_src

*** Platformer - Gorillas Basic - credits.txt
#+begin_src ruby
  # ./samples/99_genre_platformer/gorillas_basic/CREDITS.txt
  code: Amir Rajan, https://twitter.com/amirrajan
  graphics: Nick Culbertson, https://twitter.com/MobyPixel
  

#+end_src

*** Platformer - Gorillas Basic - main.rb
#+begin_src ruby
  # ./samples/99_genre_platformer/gorillas_basic/app/main.rb
  class YouSoBasicGorillas
    attr_accessor :outputs, :grid, :state, :inputs
  
    def tick
      defaults
      render
      calc
      process_inputs
    end
  
    def defaults
      outputs.background_color = [33, 32, 87]
      state.building_spacing       = 1
      state.building_room_spacing  = 15
      state.building_room_width    = 10
      state.building_room_height   = 15
      state.building_heights       = [4, 4, 6, 8, 15, 20, 18]
      state.building_room_sizes    = [5, 4, 6, 7]
      state.gravity                = 0.25
      state.first_strike         ||= :player_1
      state.buildings            ||= []
      state.holes                ||= []
      state.player_1_score       ||= 0
      state.player_2_score       ||= 0
      state.wind                 ||= 0
    end
  
    def render
      render_stage
      render_value_insertion
      render_gorillas
      render_holes
      render_banana
      render_game_over
      render_score
      render_wind
    end
  
    def render_score
      outputs.primitives << [0, 0, 1280, 31, fancy_white].solid
      outputs.primitives << [1, 1, 1279, 29].solid
      outputs.labels << [  10, 25, "Score: #{state.player_1_score}", 0, 0, fancy_white]
      outputs.labels << [1270, 25, "Score: #{state.player_2_score}", 0, 2, fancy_white]
    end
  
    def render_wind
      outputs.primitives << [640, 12, state.wind * 500 + state.wind * 10 * rand, 4, 35, 136, 162].solid
      outputs.lines     <<  [640, 30, 640, 0, fancy_white]
    end
  
    def render_game_over
      return unless state.over
      outputs.primitives << [grid.rect, 0, 0, 0, 200].solid
      outputs.primitives << [640, 370, "Game Over!!", 5, 1, fancy_white].label
      if state.winner == :player_1
        outputs.primitives << [640, 340, "Player 1 Wins!!", 5, 1, fancy_white].label
      else
        outputs.primitives << [640, 340, "Player 2 Wins!!", 5, 1, fancy_white].label
      end
    end
  
    def render_stage
      return unless state.stage_generated
      return if state.stage_rendered
  
      outputs.static_solids << [grid.rect, 33, 32, 87]
      outputs.static_solids << state.buildings.map(&:solids)
      state.stage_rendered = true
    end
  
    def render_gorilla gorilla, id
      return unless gorilla
      if state.banana && state.banana.owner == gorilla
        animation_index  = state.banana.created_at.frame_index(3, 5, false)
      end
      if !animation_index
        outputs.sprites << [gorilla.solid, "sprites/#{id}-idle.png"]
      else
        outputs.sprites << [gorilla.solid, "sprites/#{id}-#{animation_index}.png"]
      end
    end
  
    def render_gorillas
      render_gorilla state.player_1, :left
      render_gorilla state.player_2, :right
    end
  
    def render_value_insertion
      return if state.banana
      return if state.over
  
      if    state.current_turn == :player_1_angle
        outputs.labels << [  10, 710, "Angle:    #{state.player_1_angle}_",    fancy_white]
      elsif state.current_turn == :player_1_velocity
        outputs.labels << [  10, 710, "Angle:    #{state.player_1_angle}",     fancy_white]
        outputs.labels << [  10, 690, "Velocity: #{state.player_1_velocity}_", fancy_white]
      elsif state.current_turn == :player_2_angle
        outputs.labels << [1120, 710, "Angle:    #{state.player_2_angle}_",    fancy_white]
      elsif state.current_turn == :player_2_velocity
        outputs.labels << [1120, 710, "Angle:    #{state.player_2_angle}",     fancy_white]
        outputs.labels << [1120, 690, "Velocity: #{state.player_2_velocity}_", fancy_white]
      end
    end
  
    def render_banana
      return unless state.banana
      rotation = state.tick_count.%(360) * 20
      rotation *= -1 if state.banana.dx > 0
      outputs.sprites << [state.banana.x, state.banana.y, 15, 15, 'sprites/banana.png', rotation]
    end
  
    def render_holes
      outputs.sprites << state.holes.map do |s|
        animation_index = s.created_at.frame_index(7, 3, false)
        if animation_index
          [s.sprite, [s.sprite.rect, "sprites/explosion#{animation_index}.png" ]]
        else
          s.sprite
        end
      end
    end
  
    def calc
      calc_generate_stage
      calc_current_turn
      calc_banana
    end
  
    def calc_current_turn
      return if state.current_turn
  
      state.current_turn = :player_1_angle
      state.current_turn = :player_2_angle if state.first_strike == :player_2
    end
  
    def calc_generate_stage
      return if state.stage_generated
  
      state.buildings << building_prefab(state.building_spacing + -20, *random_building_size)
      8.numbers.inject(state.buildings) do |buildings, i|
        buildings <<
          building_prefab(state.building_spacing +
                          state.buildings.last.right,
                          *random_building_size)
      end
  
      building_two = state.buildings[1]
      state.player_1 = new_player(building_two.x + building_two.w.fdiv(2),
                                 building_two.h)
  
      building_nine = state.buildings[-3]
      state.player_2 = new_player(building_nine.x + building_nine.w.fdiv(2),
                                 building_nine.h)
      state.stage_generated = true
      state.wind = 1.randomize(:ratio, :sign)
    end
  
    def new_player x, y
      state.new_entity(:gorilla) do |p|
        p.x = x - 25
        p.y = y
        p.solid = [p.x, p.y, 50, 50]
      end
    end
  
    def calc_banana
      return unless state.banana
  
      state.banana.x  += state.banana.dx
      state.banana.dx += state.wind.fdiv(50)
      state.banana.y  += state.banana.dy
      state.banana.dy -= state.gravity
      banana_collision = [state.banana.x, state.banana.y, 10, 10]
  
      if state.player_1 && banana_collision.intersect_rect?(state.player_1.solid)
        state.over = true
        if state.banana.owner == state.player_2
          state.winner = :player_2
        else
          state.winner = :player_1
        end
  
        state.player_2_score += 1
      elsif state.player_2 && banana_collision.intersect_rect?(state.player_2.solid)
        state.over = true
        if state.banana.owner == state.player_2
          state.winner = :player_1
        else
          state.winner = :player_2
        end
        state.player_1_score += 1
      end
  
      if state.over
        place_hole
        return
      end
  
      return if state.holes.any? do |h|
        h.sprite.scale_rect(0.8, 0.5, 0.5).intersect_rect? [state.banana.x, state.banana.y, 10, 10]
      end
  
      return unless state.banana.y < 0 || state.buildings.any? do |b|
        b.rect.intersect_rect? [state.banana.x, state.banana.y, 1, 1]
      end
  
      place_hole
    end
  
    def place_hole
      return unless state.banana
  
      state.holes << state.new_entity(:banana) do |b|
        b.sprite = [state.banana.x - 20, state.banana.y - 20, 40, 40, 'sprites/hole.png']
      end
  
      state.banana = nil
    end
  
    def process_inputs_main
      return if state.banana
      return if state.over
  
      if inputs.keyboard.key_down.enter
        input_execute_turn
      elsif inputs.keyboard.key_down.backspace
        state.as_hash[state.current_turn] ||= ""
        state.as_hash[state.current_turn]   = state.as_hash[state.current_turn][0..-2]
      elsif inputs.keyboard.key_down.char
        state.as_hash[state.current_turn] ||= ""
        state.as_hash[state.current_turn]  += inputs.keyboard.key_down.char
      end
    end
  
    def process_inputs_game_over
      return unless state.over
      return unless inputs.keyboard.key_down.truthy_keys.any?
      state.over = false
      outputs.static_solids.clear
      state.buildings.clear
      state.holes.clear
      state.stage_generated = false
      state.stage_rendered = false
      if state.first_strike == :player_1
        state.first_strike = :player_2
      else
        state.first_strike = :player_1
      end
    end
  
    def process_inputs
      process_inputs_main
      process_inputs_game_over
    end
  
    def input_execute_turn
      return if state.banana
  
      if state.current_turn == :player_1_angle && parse_or_clear!(:player_1_angle)
        state.current_turn = :player_1_velocity
      elsif state.current_turn == :player_1_velocity && parse_or_clear!(:player_1_velocity)
        state.current_turn = :player_2_angle
        state.banana =
          new_banana(state.player_1,
                     state.player_1.x + 25,
                     state.player_1.y + 60,
                     state.player_1_angle,
                     state.player_1_velocity)
      elsif state.current_turn == :player_2_angle && parse_or_clear!(:player_2_angle)
        state.current_turn = :player_2_velocity
      elsif state.current_turn == :player_2_velocity && parse_or_clear!(:player_2_velocity)
        state.current_turn = :player_1_angle
        state.banana =
          new_banana(state.player_2,
                     state.player_2.x + 25,
                     state.player_2.y + 60,
                     180 - state.player_2_angle,
                     state.player_2_velocity)
      end
  
      if state.banana
        state.player_1_angle = nil
        state.player_1_velocity = nil
        state.player_2_angle = nil
        state.player_2_velocity = nil
      end
    end
  
    def random_building_size
      [state.building_heights.sample, state.building_room_sizes.sample]
    end
  
    def int? v
      v.to_i.to_s == v.to_s
    end
  
    def random_building_color
      [[ 99,   0, 107],
       [ 35,  64, 124],
       [ 35, 136, 162],
       ].sample
    end
  
    def random_window_color
      [[ 88,  62, 104],
       [253, 224, 187]].sample
    end
  
    def windows_for_building starting_x, floors, rooms
      floors.-(1).combinations(rooms - 1).map do |floor, room|
        [starting_x +
         state.building_room_width.*(room) +
         state.building_room_spacing.*(room + 1),
         state.building_room_height.*(floor) +
         state.building_room_spacing.*(floor + 1),
         state.building_room_width,
         state.building_room_height,
         random_window_color]
      end
    end
  
    def building_prefab starting_x, floors, rooms
      state.new_entity(:building) do |b|
        b.x      = starting_x
        b.y      = 0
        b.w      = state.building_room_width.*(rooms) +
                   state.building_room_spacing.*(rooms + 1)
        b.h      = state.building_room_height.*(floors) +
                   state.building_room_spacing.*(floors + 1)
        b.right  = b.x + b.w
        b.rect   = [b.x, b.y, b.w, b.h]
        b.solids = [[b.x - 1, b.y, b.w + 2, b.h + 1, fancy_white],
                    [b.x, b.y, b.w, b.h, random_building_color],
                    windows_for_building(b.x, floors, rooms)]
      end
    end
  
    def parse_or_clear! game_prop
      if int? state.as_hash[game_prop]
        state.as_hash[game_prop] = state.as_hash[game_prop].to_i
        return true
      end
  
      state.as_hash[game_prop] = nil
      return false
    end
  
    def new_banana owner, x, y, angle, velocity
      state.new_entity(:banana) do |b|
        b.owner     = owner
        b.x         = x
        b.y         = y
        b.angle     = angle % 360
        b.velocity  = velocity / 5
        b.dx        = b.angle.vector_x(b.velocity)
        b.dy        = b.angle.vector_y(b.velocity)
      end
    end
  
    def fancy_white
      [253, 252, 253]
    end
  end
  
  $you_so_basic_gorillas = YouSoBasicGorillas.new
  
  def tick args
    $you_so_basic_gorillas.outputs = args.outputs
    $you_so_basic_gorillas.grid    = args.grid
    $you_so_basic_gorillas.state    = args.state
    $you_so_basic_gorillas.inputs  = args.inputs
    $you_so_basic_gorillas.tick
  end

#+end_src

*** Platformer - Gorillas Basic - tests.rb
#+begin_src ruby
  # ./samples/99_genre_platformer/gorillas_basic/app/tests.rb
  $gtk.reset 100
  $gtk.supress_framerate_warning = true
  $gtk.require 'app/tests/building_generation_tests.rb'
  $gtk.tests.start

#+end_src

*** Platformer - Gorillas Basic - Tests - building_generation_tests.rb
#+begin_src ruby
  # ./samples/99_genre_platformer/gorillas_basic/app/tests/building_generation_tests.rb
  def test_solids args, assert
    game = YouSoBasicGorillas.new
    game.outputs = args.outputs
    game.grid = args.grid
    game.state = args.state
    game.inputs = args.inputs
    game.tick
    assert.true! args.state.stage_generated, "stage wasn't generated but it should have been"
    game.tick
    assert.true! args.outputs.static_solids.length > 0, "stage wasn't rendered"
    number_of_building_components = (args.state.buildings.map { |b| 2 + b.solids[2].length }.inject do |sum, v| (sum || 0) + v end)
    the_only_background = 1
    static_solids = args.outputs.static_solids.length
    assert.true! static_solids == the_only_background.+(number_of_building_components), "not all parts of the buildings and background were rendered"
  end

#+end_src

*** Platformer - Shadows - main.rb
#+begin_src ruby
  # ./samples/99_genre_platformer/shadows/app/main.rb
  class Game
    attr_gtk
  
    def tick
      defaults
      input
      calc
      render
    end
  
    def defaults
      new_game if !state.clock || state.game_over == true
    end
  
    def input
      input_entity player,
                   find_input_timeline(at: player.clock, key: :left_right),
                   find_input_timeline(at: player.clock, key: :space),
                   find_input_timeline(at: player.clock, key: :down)
  
      shadows.find_all { |shadow| entity_active? shadow }
             .each do |shadow|
               input_entity shadow,
                            find_input_timeline(at: shadow.clock, key: :left_right),
                            find_input_timeline(at: shadow.clock, key: :space),
                            find_input_timeline(at: shadow.clock, key: :down)
               end
    end
  
    def input_entity entity, left_right, jump, fall_through
      return if !entity_active? entity
  
      entity.dx += left_right
  
      if left_right == 0
        if (entity.action == :running)
          entity_set_action! entity, :standing
        end
      elsif entity.left_right != left_right && (entity_on_platform? entity)
        entity_set_action! entity, :running
      end
  
      entity.left_right = left_right
  
      entity.orientation = if left_right == -1
                             :left
                           elsif left_right == 1
                             :right
                           else
                             entity.orientation
                           end
  
      if fall_through && (entity_on_platform? entity)
        entity.jumped_at      = 0
        entity.jumped_down_at = entity.clock
        entity.jump_count    += 1
      end
  
      if jump && entity.jump_count < 3
        if entity.jump_count == 0
          entity_set_action! entity, :first_jump
        elsif entity.jump_count == 1
          entity_set_action! entity, :midair_jump
        elsif entity.jump_count == 2
          entity_set_action! entity, :midair_jump
        end
  
        entity.dy             = entity.jump_power
        entity.jumped_at      = entity.clock
        entity.jumped_down_at = 0
        entity.jump_count    += 1
      end
    end
  
    def calc
      calc_light_meter
      calc_action_history
      calc_entity player
      calc_shadows
      calc_light_crystal
      calc_render_queues
      calc_game_over
      calc_clock
    end
  
    def calc_light_meter
      state.light_meter -= 1
      d = state.light_meter_queue * 0.1
      state.light_meter += d
      state.light_meter_queue -= d
    end
  
    def calc_action_history
      state.curr_left_right     = inputs.left_right
      if state.prev_left_right != state.curr_left_right
        state.input_timeline.unshift({ at: state.clock, k: :left_right, v: state.curr_left_right })
      end
      state.prev_left_right = state.curr_left_right
  
      state.curr_space     = inputs.keyboard.key_down.space    ||
                             inputs.controller_one.key_down.a  ||
                             inputs.keyboard.key_down.up       ||
                             inputs.controller_one.key_down.b
  
      if state.prev_space != state.curr_space
        state.input_timeline.unshift({ at: state.clock, k: :space, v: state.curr_space })
      end
      state.prev_space = state.curr_space
  
      state.curr_down     = inputs.keyboard.down || inputs.controller_one.down
      if state.prev_down != state.curr_down
        state.input_timeline.unshift({ at: state.clock, k: :down, v: state.curr_down })
      end
      state.prev_down = state.curr_down
    end
  
    def calc_entity entity
      calc_entity_rect entity
      return if !entity_active? entity
      calc_entity_collision entity
      calc_entity_action entity
      calc_entity_movement entity
    end
  
    def calc_entity_rect entity
      entity.render_rect = { x: entity.x, y: entity.y, w: entity.w, h: entity.h }
      entity.rect = entity.render_rect.merge x: entity.render_rect.x + entity.render_rect.w * 0.33,
                                             w: entity.render_rect.w * 0.33
      entity.next_rect = entity.rect.merge x: entity.x + entity.dx,
                                           y: entity.y + entity.dy
      entity.prev_rect = entity.rect.merge x: entity.x - entity.dx,
                                           y: entity.y - entity.dy
      orientation_shift = 0
      if entity.orientation == :right
        orientation_shift = entity.rect.w.half
      end
      entity.hurt_rect  = entity.rect.merge y: entity.rect.y + entity.h * 0.33,
                                            x: entity.rect.x - entity.rect.w.half + orientation_shift,
                                            h: entity.rect.h * 0.33
    end
  
    def calc_entity_collision entity
      calc_entity_below entity
      calc_entity_left entity
      calc_entity_right entity
    end
  
    def calc_entity_below entity
      return unless entity.dy < 0
      tiles_below = find_tiles { |t| t.rect.top <= entity.prev_rect.y }
      collision = find_collision tiles_below, (entity.rect.merge y: entity.next_rect.y)
      return unless collision
      can_drop = true
      if entity.last_standing_at && (entity.clock - entity.last_standing_at) < 8
        can_drop = false
      end
  
      if can_drop && entity.jumped_down_at.elapsed_time(entity.clock) < 10 && !collision.impassable
        if (entity_on_platform? entity) && can_drop
          entity.dy = -1
        end
  
        entity.jump_count = 1
      else
        entity.y  = collision.rect.y + collision.rect.h
        entity.dy = 0
        entity.jump_count = 0
      end
    end
  
    def calc_entity_left entity
      return unless entity.dx < 0
      return if entity.next_rect.x > 8 - 32
      entity.x  = 8 - 32
      entity.dx = 0
    end
  
    def calc_entity_right entity
      return unless entity.dx > 0
      return if (entity.next_rect.x + entity.rect.w) < (1280 - 8 - 32)
      entity.x  = (1280 - 8 - entity.rect.w - 32)
      entity.dx = 0
    end
  
    def calc_entity_action entity
      if entity.dy < 0
        if entity.action == :midair_jump
          if entity_action_complete? entity, state.midair_jump_duration
            entity_set_action! entity, :falling
          end
        else
          entity_set_action! entity, :falling
        end
      elsif entity.dy == 0 && !(entity_on_platform? entity)
        if entity.left_right == 0
          entity_set_action! entity, :standing
        else
          entity_set_action! entity, :running
        end
      end
    end
  
    def calc_entity_movement entity
      calc_entity_dy entity
      calc_entity_dx entity
    end
  
    def calc_entity_dx entity
      entity.dx  = entity.dx.clamp(-5,  5)
      entity.dx *= 0.9
      entity.x  += entity.dx
    end
  
    def calc_entity_dy entity
      entity.y  += entity.dy
      entity.dy += state.gravity
      entity.dy += entity.dy * state.drag ** 2 * -1
    end
  
    def calc_shadows
      add_shadow! if state.clock.zmod?(300)
  
      shadows.each do |shadow|
        calc_entity shadow
        shadow.spawn_countdown -= 1 if shadow.spawn_countdown > 0
      end
    end
  
    def calc_light_crystal
      light_rect = state.light_crystal
      if player.hurt_rect.intersect_rect? light_rect
        state.jitter_fade_out_render_queue << { x:    state.light_crystal.x,
                                                y:    state.light_crystal.y,
                                                w:    state.light_crystal.w,
                                                h:    state.light_crystal.h,
                                                a:    255,
                                                path: 'sprites/light.png' }
        state.light_meter_queue += 600
        state.light_crystal = new_light_crystal
      end
    end
  
    def calc_render_queues
      state.jitter_fade_out_render_queue.each do |s|
        new_w = s.w * 1.02 ** 5
        ds = new_w - s.w
        s.w = new_w
        s.h = new_w
        s.x -= ds.half
        s.y -= ds.half
        s.a = s.a * 0.97 ** 5
      end
  
      state.jitter_fade_out_render_queue.reject! { |s| s.a <= 1 }
  
      state.game_over_render_queue.each { |s| s.a = s.a * 0.95 }
      state.game_over_render_queue.reject! { |s| s.a <= 1 }
    end
  
    def calc_game_over
      state.game_over = false
      state.game_over ||= shadows.find_all { |s| s.spawn_countdown <= 0 }
                                 .any? { |s| s.hurt_rect.intersect_rect? player.hurt_rect }
  
      state.game_over ||= state.light_meter <= 1
  
      if inputs.keyboard.key_down.r
        state.you_win = false
        state.game_over = true
      end
  
      if state.game_over
        state.you_win = false
        state.game_over = true
      end
  
      if state.light_meter >= 6000
        state.you_win = true
        state.game_over = true
      end
  
      if state.game_over
        state.game_over_render_queue.concat shadows.map { |s| s.sprite.merge(a: 255) }
        state.game_over_render_queue << player.sprite.merge(a: 255)
        state.game_over_render_queue << state.light_crystal.merge(a: 255, path: 'sprites/light.png', b: 128)
      end
    end
  
    def calc_clock
      return if state.game_over
      state.clock += 1
      player.clock += 1
      shadows.each { |s| s.clock += 1 if entity_active? s }
    end
  
    def render
      render_stage
      render_light_meter
      render_instructions
      render_render_queues
      render_light_meter_warning
      render_light_crystal
      render_entities
    end
  
    def render_stage
      outputs.background_color = [255, 255, 255]
      outputs.sprites << { x: 0,
                           y: 0,
                           w: 1280,
                           h: 720,
                           path: "sprites/stage.png",
                           a: 200 }
    end
  
    def render_light_meter
      meter_perc = state.light_meter.fdiv(6000) + (0.002 * rand)
      light_w = (1280 * meter_perc).round
      dark_w  = 1280 - light_w
      outputs.sprites << { x: 0,
                           y: 64.from_top,
                           w: light_w,
                           source_x: 0,
                           source_y: 0,
                           source_w: light_w,
                           source_h: 128,
                           h: 64,
                           path: 'sprites/meter-light.png' }
  
      outputs.sprites << { x: 1280 * meter_perc,
                           y: 64.from_top,
                           w: dark_w,
                           source_x: light_w,
                           source_y: 0,
                           source_w: dark_w,
                           source_h: 128,
                           h: 64,
                           path: 'sprites/meter-dark.png' }
    end
  
    def render_instructions
      outputs.labels << { x: 640,
                          y: 40,
                          text: '[left/right] to move, [up/space] to jump, [down] to drop through platform',
                          alignment_enum: 1 }
  
      if state.you_win
        outputs.labels << { x: 640,
                            y: 40.from_top,
                            text: 'You win!',
                            size_enum: -1,
                            alignment_enum: 1 }
      end
    end
  
    def render_render_queues
      outputs.sprites << state.jitter_fade_out_render_queue
      outputs.sprites << state.game_over_render_queue
    end
  
    def render_light_meter_warning
      return if state.light_meter >= 255
  
      outputs.primitives << { x: 0,
                              y: 0,
                              w: 1280,
                              h: 720,
                              a: 255 - state.light_meter,
                              path: :pixel,
                              r: 0,
                              g: 0,
                              b: 0 }
  
      outputs.primitives << { x: state.light_crystal.x - 32,
                              y: state.light_crystal.y - 32,
                              w: 128,
                              h: 128,
                              a: 255 - state.light_meter,
                              path: 'sprites/spotlight.png' }
    end
  
    def render_light_crystal
      jitter_sprite = { x: state.light_crystal.x + 5 * rand,
                        y: state.light_crystal.y + 5 * rand,
                        w: state.light_crystal.w + 5 * rand,
                        h: state.light_crystal.h + 5 * rand,
                        path: 'sprites/light.png' }
      outputs.primitives << jitter_sprite
    end
  
    def render_entities
      render_entity player, r: 0, g: 0, b: 0
      shadows.each { |shadow| render_entity shadow, g: 0, b: 0 }
    end
  
    def render_entity entity, r: 255, g: 255, b: 255;
      a = 255
  
      entity.sprite = nil
  
      if entity.activate_at
        activation_elapsed_time = state.clock - entity.activate_at
        if entity.activate_at > state.clock
          entity.sprite = { x: entity.initial_x + 5 * rand,
                            y: entity.initial_y + 5 * rand,
                            w: 64 + 5 * rand,
                            h: 64 + 5 * rand,
                            path: "sprites/light.png",
                            g: 0, b: 0,
                            a: a }
  
          outputs.sprites << entity.sprite
          return
        elsif !entity.activated
          entity.activated = true
          state.jitter_fade_out_render_queue << { x: entity.initial_x + 5 * rand,
                                                  y: entity.initial_y + 5 * rand,
                                                  w: 86 + 5 * rand, h: 86 + 5 * rand,
                                                  path: "sprites/light.png",
                                                  g: 0, b: 0, a: 255 }
        end
      end
  
      if entity.action == :standing
        path = "sprites/player/stand.png"
      elsif entity.action == :running
        sprint_index = entity.action_at
                             .frame_index count: 4,
                                          hold_for: 8,
                                          repeat: true,
                                          tick_count_override: entity.clock
        path = "sprites/player/run-#{sprint_index}.png"
      elsif entity.action == :first_jump
        sprint_index = entity.action_at
                             .frame_index count: 2,
                                          hold_for: 8,
                                          repeat: false,
                                          tick_count_override: entity.clock
        path = "sprites/player/jump-#{sprint_index || 1}.png"
      elsif entity.action == :midair_jump
        sprint_index = entity.action_at
                             .frame_index count: state.midair_jump_frame_count,
                                          hold_for: state.midair_jump_hold_for,
                                          repeat: false,
                                          tick_count_override: entity.clock
        path = "sprites/player/midair-jump-#{sprint_index || 8}.png"
      elsif entity.action == :falling
        path = "sprites/player/falling.png"
      end
  
      flip_horizontally = true if entity.orientation == :left
      entity.sprite = entity.render_rect.merge path: path,
                                               a: a,
                                               r: r,
                                               g: g,
                                               b: b,
                                               flip_horizontally: flip_horizontally
      outputs.sprites << entity.sprite
    end
  
    def new_game
      state.clock                   = 0
      state.game_over               = false
      state.gravity                 = -0.4
      state.drag                    = 0.15
  
      state.activation_time         = 90
      state.light_meter             = 600
      state.light_meter_queue       = 0
  
      state.midair_jump_frame_count = 9
      state.midair_jump_hold_for    = 6
      state.midair_jump_duration    = state.midair_jump_frame_count * state.midair_jump_hold_for
  
      state.tiles                   = [
        { impassable: true, x: 0, y: 0, w: 1280, h: 8, path: :pixel, r: 0, g: 0, b: 0 },
        { impassable: true, x: 0, y: 0, w: 8, h: 1500, path: :pixel, r: 0, g: 0, b: 0 },
        { impassable: true, x: 1280 - 8, y: 0, w: 8, h: 1500, path: :pixel, r: 0, g: 0, b: 0 },
  
        { x: 80 + 320 + 80,            y: 128, w: 320, h: 8, path: :pixel, r: 0, g: 0, b: 0 },
        { x: 80 + 320 + 80 + 320 + 80, y: 192, w: 320, h: 8, path: :pixel, r: 0, g: 0, b: 0 },
  
        { x: 160,                      y: 320, w: 400, h: 8, path: :pixel, r: 0, g: 0, b: 0 },
        { x: 160 + 400 + 160,          y: 400, w: 400, h: 8, path: :pixel, r: 0, g: 0, b: 0 },
  
        { x: 320,                      y: 600, w: 320, h: 8, path: :pixel, r: 0, g: 0, b: 0 },
  
        { x: 8, y: 500, w: 100, h: 8, path: :pixel, r: 0, g: 0, b: 0 },
  
        { x: 8, y: 60, w: 100, h: 8, path: :pixel, r: 0, g: 0, b: 0 },
      ]
  
      state.player                = new_entity
      state.player.jump_count     = 1
      state.player.jumped_at      = state.player.clock
      state.player.jumped_down_at = 0
  
      state.shadows   = []
  
      state.input_timeline = [
        { at: 0, k: :left_right, v: inputs.left_right },
        { at: 0, k: :space,      v: false },
        { at: 0, k: :down,       v: false },
      ]
  
      state.jitter_fade_out_render_queue   = []
      state.game_over_render_queue       ||= []
  
      state.light_crystal = new_light_crystal
    end
  
    def new_light_crystal
      r = { x: 124 + rand(1000), y: 135 + rand(500), w: 64, h: 64 }
      return new_light_crystal if tiles.any? { |t| t.intersect_rect? r }
      return new_light_crystal if (player.x - r.x).abs < 200
      r
    end
  
    def entity_active? entity
      return true unless entity.activate_at
      return entity.activate_at <= state.clock
    end
  
    def add_shadow!
      s = new_entity(from_entity: player)
      s.activate_at = state.clock + state.activation_time * (shadows.length + 1)
      s.spawn_countdown = state.activation_time
      shadows << s
    end
  
    def find_input_timeline at:, key:;
      state.input_timeline.find { |t| t.at <= at && t.k == key }.v
    end
  
    def new_entity from_entity: nil
      pe = state.new_entity(:body)
      pe.w                  = 96
      pe.h                  = 96
      pe.jump_power         = 12
      pe.y                  = 500
      pe.x                  = 640 - 8
      pe.initial_x          = pe.x
      pe.initial_y          = pe.y
      pe.dy                 = 0
      pe.dx                 = 0
      pe.jumped_down_at     = 0
      pe.jumped_at          = 0
      pe.jump_count         = 0
      pe.clock              = state.clock
      pe.orientation        = :right
      pe.action             = :falling
      pe.action_at          = state.clock
      pe.left_right         = 0
      if from_entity
        pe.w              = from_entity.w
        pe.h              = from_entity.h
        pe.jump_power     = from_entity.jump_power
        pe.x              = from_entity.x
        pe.y              = from_entity.y
        pe.initial_x      = from_entity.x
        pe.initial_y      = from_entity.y
        pe.dy             = from_entity.dy
        pe.dx             = from_entity.dx
        pe.jumped_down_at = from_entity.jumped_down_at
        pe.jumped_at      = from_entity.jumped_at
        pe.orientation    = from_entity.orientation
        pe.action         = from_entity.action
        pe.action_at      = from_entity.action_at
        pe.jump_count     = from_entity.jump_count
        pe.left_right     = from_entity.left_right
      end
      pe
    end
  
    def entity_on_platform? entity
      entity.action == :standing || entity.action == :running
    end
  
    def entity_action_complete? entity, action_duration
      entity.action_at.elapsed_time(entity.clock) + 1 >= action_duration
    end
  
    def entity_set_action! entity, action
      entity.action = action
      entity.action_at = entity.clock
      entity.last_standing_at = entity.clock if action == :standing
    end
  
    def player
      state.player
    end
  
    def shadows
      state.shadows
    end
  
    def tiles
      state.tiles
    end
  
    def find_tiles &block
      tiles.find_all(&block)
    end
  
    def find_collision tiles, target
      tiles.find { |t| t.rect.intersect_rect? target }
    end
  end
  
  def boot args
    $game = Game.new
  end
  
  def tick args
    $game.args = args
    $game.tick
  end
  
  def reset args
    $game = Game.new
  end

#+end_src

*** Platformer - Shadows - Metadata - ios_metadata.txt
#+begin_src ruby
  # ./samples/99_genre_platformer/shadows/metadata/ios_metadata.txt
  teamid=L7H57V9CRD
  appid=com.scratchworkdevelopment.sandbox
  appname=DragonRuby
  version=1.0
  devcert=iPhone Developer: Amirali Rajan (P2B6225J87)
  prodcert=

#+end_src

*** Platformer - The Little Probe - main.rb
#+begin_src ruby
  # ./samples/99_genre_platformer/the_little_probe/app/main.rb
  class FallingCircle
    attr_gtk
  
    def tick
      fiddle
      defaults
      render
      input
      calc
    end
  
    def fiddle
      state.gravity     = -0.02
      circle.radius     = 15
      circle.elasticity = 0.4
      camera.follow_speed = 0.4 * 0.4
    end
  
    def render
      render_stage_editor
      render_debug
      render_game
    end
  
    def defaults
      if state.tick_count == 0
        outputs.sounds << "sounds/bg.ogg"
      end
  
      state.storyline ||= [
        { text: "<- -> to aim, hold space to charge",                            distance_gate: 0 },
        { text: "the little probe - by @amirrajan, made with DragonRuby Game Toolkit", distance_gate: 0 },
        { text: "mission control, this is sasha. landing on europa successful.", distance_gate: 0 },
        { text: "operation \"find earth 2.0\", initiated at 8-29-2036 14:00.",   distance_gate: 0 },
        { text: "jupiter's sure is beautiful...",   distance_gate: 4000 },
        { text: "hmm, it seems there's some kind of anomoly in the sky",   distance_gate: 7000 },
        { text: "dancing lights, i'll call them whisps.",   distance_gate: 8000 },
        { text: "#todo... look i ran out of time -_-",   distance_gate: 9000 },
        { text: "there's never enough time",   distance_gate: 9000 },
        { text: "the game jam was fun though ^_^",   distance_gate: 10000 },
      ]
  
      load_level force: args.state.tick_count == 0
      state.line_mode            ||= :terrain
  
      state.sound_index          ||= 1
      circle.potential_lift      ||= 0
      circle.angle               ||= 90
      circle.check_point_at      ||= -1000
      circle.game_over_at        ||= -1000
      circle.x                   ||= -485
      circle.y                   ||= 12226
      circle.check_point_x       ||= circle.x
      circle.check_point_y       ||= circle.y
      circle.dy                  ||= 0
      circle.dx                  ||= 0
      circle.previous_dy         ||= 0
      circle.previous_dx         ||= 0
      circle.angle               ||= 0
      circle.after_images        ||= []
      circle.terrains_to_monitor ||= {}
      circle.impact_history      ||= []
  
      camera.x                   ||= 0
      camera.y                   ||= 0
      camera.target_x            ||= 0
      camera.target_y            ||= 0
      state.snaps                ||= { }
      state.snap_number            = 10
  
      args.state.storyline_x ||= -1000
      args.state.storyline_y ||= -1000
    end
  
    def render_game
      outputs.background_color = [0, 0, 0]
      outputs.sprites << [-circle.x + 1100,
                          -circle.y - 100,
                          2416 * 4,
                          3574 * 4,
                          'sprites/jupiter.png']
      outputs.sprites << [-circle.x,
                          -circle.y,
                          2416 * 4,
                          3574 * 4,
                          'sprites/level.png']
      outputs.sprites << state.whisp_queue
      render_aiming_retical
      render_circle
      render_notification
    end
  
    def render_notification
      toast_length = 500
      if circle.game_over_at.elapsed_time < toast_length
        label_text = "..."
      elsif circle.check_point_at.elapsed_time > toast_length
        args.state.current_storyline = nil
        return
      end
      if circle.check_point_at &&
         circle.check_point_at.elapsed_time == 1 &&
         !args.state.current_storyline
         if args.state.storyline.length > 0 && args.state.distance_traveled > args.state.storyline[0][:distance_gate]
           args.state.current_storyline = args.state.storyline.shift[:text]
           args.state.distance_traveled ||= 0
           args.state.storyline_x = circle.x
           args.state.storyline_y = circle.y
         end
        return unless args.state.current_storyline
      end
      label_text = args.state.current_storyline
      return unless label_text
      x = circle.x + camera.x
      y = circle.y + camera.y - 40
      w = 900
      h = 30
      outputs.primitives << [x - w.idiv(2), y - h, w, h, 255, 255, 255, 255].solid
      outputs.primitives << [x - w.idiv(2), y - h, w, h, 0, 0, 0, 255].border
      outputs.labels << [x, y - 4, label_text, 1, 1, 0, 0, 0, 255]
    end
  
    def render_aiming_retical
      outputs.sprites << [state.camera.x + circle.x + circle.angle.vector_x(circle.potential_lift * 10) - 5,
                          state.camera.y + circle.y + circle.angle.vector_y(circle.potential_lift * 10) - 5,
                          10, 10, 'sprites/circle-orange.png']
      outputs.sprites << [state.camera.x + circle.x + circle.angle.vector_x(circle.radius * 3) - 5,
                          state.camera.y + circle.y + circle.angle.vector_y(circle.radius * 3) - 5,
                          10, 10, 'sprites/circle-orange.png', 0, 128]
      if rand > 0.9
        outputs.sprites << [state.camera.x + circle.x + circle.angle.vector_x(circle.radius * 3) - 5,
                            state.camera.y + circle.y + circle.angle.vector_y(circle.radius * 3) - 5,
                            10, 10, 'sprites/circle-white.png', 0, 128]
      end
    end
  
    def render_circle
      outputs.sprites << circle.after_images.map do |ai|
        ai.merge(x: ai.x + state.camera.x - circle.radius,
                 y: ai.y + state.camera.y - circle.radius,
                 w: circle.radius * 2,
                 h: circle.radius * 2,
                 path: 'sprites/circle-white.png')
      end
  
      outputs.sprites << [(circle.x - circle.radius) + state.camera.x,
                          (circle.y - circle.radius) + state.camera.y,
                          circle.radius * 2,
                          circle.radius * 2,
                          'sprites/probe.png']
    end
  
    def render_debug
      return unless state.debug_mode
  
      outputs.labels << [10, 30, state.line_mode, 0, 0, 0, 0, 0]
      outputs.labels << [12, 32, state.line_mode, 0, 0, 255, 255, 255]
  
      args.outputs.lines << trajectory(circle).line.to_hash.tap do |h|
        h[:x] += state.camera.x
        h[:y] += state.camera.y
        h[:x2] += state.camera.x
        h[:y2] += state.camera.y
      end
  
      outputs.primitives << state.terrain.find_all do |t|
        circle.x.between?(t.x - 640, t.x2 + 640) || circle.y.between?(t.y - 360, t.y2 + 360)
      end.map do |t|
        [
          t.line.associate(r: 0, g: 255, b: 0) do |h|
            h.x  += state.camera.x
            h.y  += state.camera.y
            h.x2 += state.camera.x
            h.y2 += state.camera.y
            if circle.rect.intersect_rect? t[:rect]
              h[:r] = 255
              h[:g] = 0
            end
            h
          end,
          t[:rect].border.associate(r: 255, g: 0, b: 0) do |h|
            h.x += state.camera.x
            h.y += state.camera.y
            h.b = 255 if line_near_rect? circle.rect, t
            h
          end
        ]
      end
  
      outputs.primitives << state.lava.find_all do |t|
        circle.x.between?(t.x - 640, t.x2 + 640) || circle.y.between?(t.y - 360, t.y2 + 360)
      end.map do |t|
        [
          t.line.associate(r: 0, g: 0, b: 255) do |h|
            h.x  += state.camera.x
            h.y  += state.camera.y
            h.x2 += state.camera.x
            h.y2 += state.camera.y
            if circle.rect.intersect_rect? t[:rect]
              h[:r] = 255
              h[:b] = 0
            end
            h
          end,
          t[:rect].border.associate(r: 255, g: 0, b: 0) do |h|
            h.x += state.camera.x
            h.y += state.camera.y
            h.b = 255 if line_near_rect? circle.rect, t
            h
          end
        ]
      end
  
      if state.god_mode
        border = circle.rect.merge(x: circle.rect.x + state.camera.x,
                                   y: circle.rect.y + state.camera.y,
                                   g: 255)
      else
        border = circle.rect.merge(x: circle.rect.x + state.camera.x,
                                   y: circle.rect.y + state.camera.y,
                                   b: 255)
      end
  
      outputs.borders << border
  
      overlapping ||= {}
  
      circle.impact_history.each do |h|
        label_mod = 300
        x = (h[:body][:x].-(150).idiv(label_mod)) * label_mod + camera.x
        y = (h[:body][:y].+(150).idiv(label_mod)) * label_mod + camera.y
        10.times do
          if overlapping[x] && overlapping[x][y]
            y -= 52
          else
            break
          end
        end
  
        overlapping[x] ||= {}
        overlapping[x][y] ||= true
        outputs.primitives << [x, y - 25, 300, 50, 0, 0, 0, 128].solid
        outputs.labels << [x + 10, y + 24, "dy: %.2f" % h[:body][:new_dy], -2, 0, 255, 255, 255]
        outputs.labels << [x + 10, y +  9, "dx: %.2f" % h[:body][:new_dx], -2, 0, 255, 255, 255]
        outputs.labels << [x + 10, y -  5, " ?: #{h[:body][:new_reason]}", -2, 0, 255, 255, 255]
  
        outputs.labels << [x + 100, y + 24, "angle: %.2f" % h[:impact][:angle], -2, 0, 255, 255, 255]
        outputs.labels << [x + 100, y + 9, "m(l): %.2f" % h[:terrain][:slope], -2, 0, 255, 255, 255]
        outputs.labels << [x + 100, y - 5, "m(c): %.2f" % h[:body][:slope], -2, 0, 255, 255, 255]
  
        outputs.labels << [x + 200, y + 24, "ray: #{h[:impact][:ray]}", -2, 0, 255, 255, 255]
        outputs.labels << [x + 200, y +  9, "nxt: #{h[:impact][:ray_next]}", -2, 0, 255, 255, 255]
        outputs.labels << [x + 200, y -  5, "typ: #{h[:impact][:type]}", -2, 0, 255, 255, 255]
      end
  
      if circle.floor
        outputs.labels << [circle.x + camera.x + 30, circle.y + camera.y + 100, "point: #{circle.floor_point.slice(:x, :y).values}", -2, 0]
        outputs.labels << [circle.x + camera.x + 31, circle.y + camera.y + 101, "point: #{circle.floor_point.slice(:x, :y).values}", -2, 0, 255, 255, 255]
        outputs.labels << [circle.x + camera.x + 30, circle.y + camera.y +  85, "circle: #{circle.as_hash.slice(:x, :y).values}", -2, 0]
        outputs.labels << [circle.x + camera.x + 31, circle.y + camera.y +  86, "circle: #{circle.as_hash.slice(:x, :y).values}", -2, 0, 255, 255, 255]
        outputs.labels << [circle.x + camera.x + 30, circle.y + camera.y +  70, "rel: #{circle.floor_relative_x} #{circle.floor_relative_y}", -2, 0]
        outputs.labels << [circle.x + camera.x + 31, circle.y + camera.y +  71, "rel: #{circle.floor_relative_x} #{circle.floor_relative_y}", -2, 0, 255, 255, 255]
      end
    end
  
    def render_stage_editor
      return unless state.god_mode
      return unless state.point_one
      args.lines << [state.point_one, inputs.mouse.point, 0, 255, 255]
    end
  
    def trajectory body
      [body.x + body.dx,
       body.y + body.dy,
       body.x + body.dx * 1000,
       body.y + body.dy * 1000,
       0, 255, 255]
    end
  
    def lengthen_line line, num
      line = normalize_line(line)
      slope = geometry.line_slope(line, replace_infinity: 10).abs
      if slope < 2
        [line.x - num, line.y, line.x2 + num, line.y2].line.to_hash
      else
        [line.x, line.y, line.x2, line.y2].line.to_hash
      end
    end
  
    def normalize_line line
      if line.x > line.x2
        x  = line.x2
        y  = line.y2
        x2 = line.x
        y2 = line.y
      else
        x  = line.x
        y  = line.y
        x2 = line.x2
        y2 = line.y2
      end
      [x, y, x2, y2]
    end
  
    def rect_for_line line
      if line.x > line.x2
        x  = line.x2
        y  = line.y2
        x2 = line.x
        y2 = line.y
      else
        x  = line.x
        y  = line.y
        x2 = line.x2
        y2 = line.y2
      end
  
      w = x2 - x
      h = y2 - y
  
      if h < 0
        y += h
        h = h.abs
      end
  
      if w < circle.radius
        x -= circle.radius
        w = circle.radius * 2
      end
  
      if h < circle.radius
        y -= circle.radius
        h = circle.radius * 2
      end
  
      { x: x, y: y, w: w, h: h }
    end
  
    def snap_to_grid x, y, snaps
      snap_number = 10
      x = x.to_i
      y = y.to_i
  
      x_floor = x.idiv(snap_number) * snap_number
      x_mod   = x % snap_number
      x_ceil  = (x.idiv(snap_number) + 1) * snap_number
  
      y_floor = y.idiv(snap_number) * snap_number
      y_mod   = y % snap_number
      y_ceil  = (y.idiv(snap_number) + 1) * snap_number
  
      if snaps[x_floor]
        x_result = x_floor
      elsif snaps[x_ceil]
        x_result = x_ceil
      elsif x_mod < snap_number.idiv(2)
        x_result = x_floor
      else
        x_result = x_ceil
      end
  
      snaps[x_result] ||= {}
  
      if snaps[x_result][y_floor]
        y_result = y_floor
      elsif snaps[x_result][y_ceil]
        y_result = y_ceil
      elsif y_mod < snap_number.idiv(2)
        y_result = y_floor
      else
        y_result = y_ceil
      end
  
      snaps[x_result][y_result] = true
      return [x_result, y_result]
  
    end
  
    def snap_line line
      x, y, x2, y2 = line
    end
  
    def string_to_line s
      x, y, x2, y2 = s.split(',').map(&:to_f)
  
      if x > x2
        x2, x = x, x2
        y2, y = y, y2
      end
  
      x, y = snap_to_grid x, y, state.snaps
      x2, y2 = snap_to_grid x2, y2, state.snaps
      [x, y, x2, y2].line.to_hash
    end
  
    def load_lines file
      return unless state.snaps
      data = gtk.read_file(file) || ""
      data.each_line
          .reject { |l| l.strip.length == 0 }
          .map { |l| string_to_line l }
          .map { |h| h.merge(rect: rect_for_line(h))  }
    end
  
    def load_terrain
      load_lines 'data/level.txt'
    end
  
    def load_lava
      load_lines 'data/level_lava.txt'
    end
  
    def load_level force: false
      if force
        state.snaps = {}
        state.terrain = load_terrain
        state.lava = load_lava
      else
        state.terrain ||= load_terrain
        state.lava ||= load_lava
      end
    end
  
    def save_lines lines, file
      s = lines.map do |l|
        "#{l.x1},#{l.y1},#{l.x2},#{l.y2}"
      end.join("\n")
      gtk.write_file(file, s)
    end
  
    def save_level
      save_lines(state.terrain, 'level.txt')
      save_lines(state.lava, 'level_lava.txt')
      load_level force: true
    end
  
    def line_near_rect? rect, terrain
      geometry.intersect_rect?(rect, terrain[:rect])
    end
  
    def point_within_line? point, line
      return false if !point
      return false if !line
      return true
    end
  
    def calc_impacts x, dx, y, dy, radius
      results = { }
      results[:x] = x
      results[:y] = y
      results[:dx] = x
      results[:dy] = y
      results[:point] = { x: x, y: y }
      results[:rect] = { x: x - radius, y: y - radius, w: radius * 2, h: radius * 2 }
      results[:trajectory] = trajectory(results)
      results[:impacts] = terrain.find_all { |t| t && (line_near_rect? results[:rect], t) }.map do |t|
        {
          terrain: t,
          point: geometry.line_intersect(results[:trajectory], t, replace_infinity: 1000),
          type: :terrain
        }
      end.reject { |t| !point_within_line? t[:point], t[:terrain] }
  
      results[:impacts] += lava.find_all { |t| line_near_rect? results[:rect], t }.map do |t|
        {
          terrain: t,
          point: geometry.line_intersect(results[:trajectory], t, replace_infinity: 1000),
          type: :lava
        }
      end.reject { |t| !t || (!point_within_line? t[:point], t[:terrain]) }
  
      results
    end
  
    def calc_potential_impacts
      impact_results = calc_impacts circle.x, circle.dx, circle.y, circle.dy, circle.radius
      circle.rect = impact_results[:rect]
      circle.trajectory = impact_results[:trajectory]
      circle.impacts = impact_results[:impacts]
    end
  
    def calc_terrains_to_monitor
      return unless circle.impacts
      circle.impact = nil
      circle.impacts.each do |i|
        circle.terrains_to_monitor[i[:terrain]] ||= {
          ray_start: geometry.ray_test(circle, i[:terrain]),
        }
  
        circle.terrains_to_monitor[i[:terrain]][:ray_current] = geometry.ray_test(circle, i[:terrain])
        if circle.terrains_to_monitor[i[:terrain]][:ray_start] != circle.terrains_to_monitor[i[:terrain]][:ray_current]
          if circle.x.between?(i[:terrain].x, i[:terrain].x2) || circle.y.between?(i[:terrain].y, i[:terrain].y2)
            circle.impact = i
            circle.ray_current = circle.terrains_to_monitor[i[:terrain]][:ray_current]
          end
        end
      end
    end
  
    def impact_result body, impact
      infinity_alias = 1000
      r = {
        body: {},
        terrain: {},
        impact: {}
      }
  
      r[:body][:line] = body.trajectory.dup
      r[:body][:slope] = geometry.line_slope(body.trajectory, replace_infinity: infinity_alias)
      r[:body][:slope_sign] = r[:body][:slope].sign
      r[:body][:x] = body.x
      r[:body][:y] = body.y
      r[:body][:dy] = body.dy
      r[:body][:dx] = body.dx
  
      r[:terrain][:line] = impact[:terrain].dup
      r[:terrain][:slope] = geometry.line_slope(impact[:terrain], replace_infinity: infinity_alias)
      r[:terrain][:slope_sign] = r[:terrain][:slope].sign
  
      r[:impact][:angle] = geometry.angle_between_lines(body.trajectory, impact[:terrain], replace_infinity: infinity_alias)
      r[:impact][:point] = { x: impact[:point].x, y: impact[:point].y }
      r[:impact][:same_slope_sign] = r[:body][:slope_sign] == r[:terrain][:slope_sign]
      r[:impact][:ray] = body.ray_current
      r[:body][:new_on_floor] = body.on_floor
      r[:body][:new_floor] = r[:terrain][:line]
  
      if r[:impact][:angle].abs < 90 && r[:terrain][:slope].abs < 3
        play_sound
        r[:body][:new_dy] = r[:body][:dy] * circle.elasticity * -1
        r[:body][:new_dx] = r[:body][:dx] * circle.elasticity
        r[:impact][:type] = :horizontal
        r[:body][:new_reason] = "-"
      elsif r[:impact][:angle].abs < 90 && r[:terrain][:slope].abs > 3
        play_sound
        r[:body][:new_dy] = r[:body][:dy] * 1.1
        r[:body][:new_dx] = r[:body][:dx] * -circle.elasticity
        r[:impact][:type] = :vertical
        r[:body][:new_reason] = "|"
      else
        play_sound
        r[:body][:new_dx] = r[:body][:dx] * -circle.elasticity
        r[:body][:new_dy] = r[:body][:dy] * -circle.elasticity
        r[:impact][:type] = :slanted
        r[:body][:new_reason] = "/"
      end
  
      r[:impact][:energy] = r[:body][:new_dx].abs + r[:body][:new_dy].abs
  
      if r[:impact][:energy] <= 0.3 && r[:terrain][:slope].abs < 4
        r[:body][:new_dx] = 0
        r[:body][:new_dy] = 0
        r[:impact][:energy] = 0
        r[:body][:new_on_floor] = true
        r[:body][:new_floor] = r[:terrain][:line]
        r[:body][:new_reason] = "0"
      end
  
      r[:impact][:ray_next] = geometry.ray_test({ x: r[:body][:x] - (r[:body][:dx] * 1.1) + r[:body][:new_dx],
                                                  y: r[:body][:y] - (r[:body][:dy] * 1.1) + r[:body][:new_dy] + state.gravity },
                                                r[:terrain][:line])
  
      if r[:impact][:ray_next] == r[:impact][:ray]
        r[:body][:new_dx] *= -1
        r[:body][:new_dy] *= -1
        r[:body][:new_reason] = "clip"
      end
  
      r
    end
  
    def game_over!
      circle.x = circle.check_point_x
      circle.y = circle.check_point_y
      circle.dx = 0
      circle.dy = 0
      circle.game_over_at = state.tick_count
    end
  
    def not_game_over!
      impact_history_entry = impact_result circle, circle.impact
      circle.impact_history << impact_history_entry
      circle.x -= circle.dx * 1.1
      circle.y -= circle.dy * 1.1
      circle.dx = impact_history_entry[:body][:new_dx]
      circle.dy = impact_history_entry[:body][:new_dy]
      circle.on_floor = impact_history_entry[:body][:new_on_floor]
  
      if circle.on_floor
        circle.check_point_at = state.tick_count
        circle.check_point_x = circle.x
        circle.check_point_y = circle.y
      end
  
      circle.previous_floor = circle.floor || {}
      circle.floor = impact_history_entry[:body][:new_floor] || {}
      circle.floor_point = impact_history_entry[:impact][:point]
      if circle.floor.slice(:x, :y, :x2, :y2) != circle.previous_floor.slice(:x, :y, :x2, :y2)
        new_relative_x = if circle.dx > 0
                           :right
                         elsif circle.dx < 0
                           :left
                         else
                           nil
                         end
  
        new_relative_y = if circle.dy > 0
                           :above
                         elsif circle.dy < 0
                           :below
                         else
                           nil
                         end
  
        circle.floor_relative_x = new_relative_x
        circle.floor_relative_y = new_relative_y
      end
  
      circle.impact = nil
      circle.terrains_to_monitor.clear
    end
  
    def calc_physics
      if args.state.god_mode
        calc_potential_impacts
        calc_terrains_to_monitor
        return
      end
  
      if circle.y < -700
        game_over
        return
      end
  
      return if state.game_over
      return if circle.on_floor
      circle.previous_dy = circle.dy
      circle.previous_dx = circle.dx
      circle.x  += circle.dx
      circle.y  += circle.dy
      args.state.distance_traveled ||= 0
      args.state.distance_traveled += circle.dx.abs + circle.dy.abs
      circle.dy += state.gravity
      calc_potential_impacts
      calc_terrains_to_monitor
      return unless circle.impact
      if circle.impact && circle.impact[:type] == :lava
        game_over!
      else
        not_game_over!
      end
    end
  
    def input_god_mode
      state.debug_mode = !state.debug_mode if inputs.keyboard.key_down.forward_slash
  
      # toggle god mode
      if inputs.keyboard.key_down.g
        state.god_mode = !state.god_mode
        state.potential_lift = 0
        circle.floor = nil
        circle.floor_point = nil
        circle.floor_relative_x = nil
        circle.floor_relative_y = nil
        circle.impact = nil
        circle.terrains_to_monitor.clear
        return
      end
  
      return unless state.god_mode
  
      circle.x = circle.x.to_i
      circle.y = circle.y.to_i
  
      # move god circle
      if inputs.keyboard.left || inputs.keyboard.a
        circle.x -= 20
      elsif inputs.keyboard.right || inputs.keyboard.d || inputs.keyboard.f
        circle.x += 20
      end
  
      if inputs.keyboard.up || inputs.keyboard.w
        circle.y += 20
      elsif inputs.keyboard.down || inputs.keyboard.s
        circle.y -= 20
      end
  
      # delete terrain
      if inputs.keyboard.key_down.x
        calc_terrains_to_monitor
        state.terrain = state.terrain.reject do |t|
          t[:rect].intersect_rect? circle.rect
        end
  
        state.lava = state.lava.reject do |t|
          t[:rect].intersect_rect? circle.rect
        end
  
        calc_potential_impacts
        save_level
      end
  
      # change terrain type
      if inputs.keyboard.key_down.l
        if state.line_mode == :terrain
          state.line_mode = :lava
        else
          state.line_mode = :terrain
        end
      end
  
      if inputs.mouse.click && !state.point_one
        state.point_one = inputs.mouse.click.point
      elsif inputs.mouse.click && state.point_one
        l = [*state.point_one, *inputs.mouse.click.point]
        l = [l.x  - state.camera.x,
             l.y  - state.camera.y,
             l.x2 - state.camera.x,
             l.y2 - state.camera.y].line.to_hash
        l[:rect] = rect_for_line l
        if state.line_mode == :terrain
          state.terrain << l
        else
          state.lava << l
        end
        save_level
        next_x = inputs.mouse.click.point.x - 640
        next_y = inputs.mouse.click.point.y - 360
        circle.x += next_x
        circle.y += next_y
        state.point_one = nil
      elsif inputs.keyboard.one
        state.point_one = [circle.x + camera.x, circle.y+ camera.y]
      end
  
      # cancel chain lines
      if inputs.keyboard.key_down.nine || inputs.keyboard.key_down.escape || inputs.keyboard.key_up.six || inputs.keyboard.key_up.one
        state.point_one = nil
      end
    end
  
    def play_sound
      return if state.sound_debounce > 0
      state.sound_debounce = 5
      outputs.sounds << "sounds/03#{"%02d" % state.sound_index}.wav"
      state.sound_index += 1
      if state.sound_index > 21
        state.sound_index = 1
      end
    end
  
    def input_game
      if inputs.keyboard.down || inputs.keyboard.space
        circle.potential_lift += 0.03
        circle.potential_lift = circle.potential_lift.lesser(10)
      elsif inputs.keyboard.key_up.down || inputs.keyboard.key_up.space
        play_sound
        circle.dy += circle.angle.vector_y circle.potential_lift
        circle.dx += circle.angle.vector_x circle.potential_lift
  
        if circle.on_floor
          if circle.floor_relative_y == :above
            circle.y += circle.potential_lift.abs * 2
          elsif circle.floor_relative_y == :below
            circle.y -= circle.potential_lift.abs * 2
          end
        end
  
        circle.on_floor = false
        circle.potential_lift = 0
        circle.terrains_to_monitor.clear
        circle.impact_history.clear
        circle.impact = nil
        calc_physics
      end
  
      # aim probe
      if inputs.keyboard.right || inputs.keyboard.a
        circle.angle -= 2
      elsif inputs.keyboard.left || inputs.keyboard.d
        circle.angle += 2
      end
    end
  
    def input
      input_god_mode
      input_game
    end
  
    def calc_camera
      state.camera.target_x = 640 - circle.x
      state.camera.target_y = 360 - circle.y
      xdiff = state.camera.target_x - state.camera.x
      ydiff = state.camera.target_y - state.camera.y
      state.camera.x += xdiff * camera.follow_speed
      state.camera.y += ydiff * camera.follow_speed
    end
  
    def calc
      state.sound_debounce ||= 0
      state.sound_debounce -= 1
      state.sound_debounce = 0 if state.sound_debounce < 0
      if state.god_mode
        circle.dy *= 0.1
        circle.dx *= 0.1
      end
      calc_camera
      state.whisp_queue ||= []
      if state.tick_count.mod_zero?(4)
        state.whisp_queue << {
          x: -300,
          y: 1400 * rand,
          speed: 2.randomize(:ratio) + 3,
          w: 20,
          h: 20, path: 'sprites/whisp.png',
          a: 0,
          created_at: state.tick_count,
          angle: 0,
          r: 100,
          g: 128 + 128 * rand,
          b: 128 + 128 * rand
        }
      end
  
      state.whisp_queue.each do |w|
        w.x += w[:speed] * 2
        w.x -= circle.dx * 0.3
        w.y -= w[:speed]
        w.y -= circle.dy * 0.3
        w.angle += w[:speed]
        w.a = w[:created_at].ease(30) * 255
      end
  
      state.whisp_queue = state.whisp_queue.reject { |w| w[:x] > 1280 }
  
      if state.tick_count.mod_zero?(2) && (circle.dx != 0 || circle.dy != 0)
        circle.after_images << {
          x: circle.x,
          y: circle.y,
          w: circle.radius,
          h: circle.radius,
          a: 255,
          created_at: state.tick_count
        }
      end
  
      circle.after_images.each do |ai|
        ai.a = ai[:created_at].ease(10, :flip) * 255
      end
  
      circle.after_images = circle.after_images.reject { |ai| ai[:created_at].elapsed_time > 10 }
      calc_physics
    end
  
    def circle
      state.circle
    end
  
    def camera
      state.camera
    end
  
    def terrain
      state.terrain
    end
  
    def lava
      state.lava
    end
  end
  
  # $gtk.reset
  
  def tick args
    args.outputs.background_color = [0, 0, 0]
    if args.inputs.keyboard.r
      args.gtk.reset
      return
    end
    # uncomment the line below to slow down the game so you
    # can see each tick as it passes
    # args.gtk.slowmo! 30
    $game ||= FallingCircle.new
    $game.args = args
    $game.tick
  end
  
  def reset
    $game = nil
  end

#+end_src

*** Platformer - The Little Probe - Data - level.txt
#+begin_src ruby
  # ./samples/99_genre_platformer/the_little_probe/data/level.txt
  640,8840,1180,8840
  -60,10220,0,9960
  -60,10220,0,10500
  0,10500,0,10780
  0,10780,40,10900
  500,10920,760,10960
  300,10560,820,10600
  420,10320,700,10300
  820,10600,1500,10600
  1500,10600,1940,10600
  1940,10600,2380,10580
  2380,10580,2800,10620
  2240,11080,2480,11020
  2000,11120,2240,11080
  1760,11180,2000,11120
  1620,11180,1760,11180
  1500,11220,1620,11180
  1180,11280,1340,11220
  1040,11240,1180,11280
  840,11280,1040,11240
  640,11280,840,11280
  500,11220,640,11280
  420,11140,500,11220
  240,11100,420,11140
  100,11120,240,11100
  0,11180,100,11120
  -160,11220,0,11180
  -260,11240,-160,11220
  1340,11220,1500,11220
  960,13300,1280,13060
  1280,13060,1540,12860
  1540,12860,1820,12700
  1820,12700,2080,12520
  2080,12520,2240,12400
  2240,12400,2240,12240
  2240,12240,2400,12080
  2400,12080,2560,11920
  2560,11920,2640,11740
  2640,11740,2740,11580
  2740,11580,2800,11400
  2800,11400,2800,11240
  2740,11140,2800,11240
  2700,11040,2740,11140
  2700,11040,2740,10960
  2740,10960,2740,10920
  2700,10900,2740,10920
  2380,10900,2700,10900
  2040,10920,2380,10900
  1720,10940,2040,10920
  1380,11000,1720,10940
  1180,10980,1380,11000
  900,10980,1180,10980
  760,10960,900,10980
  240,10960,500,10920
  40,10900,240,10960
  0,9700,0,9960
  -60,9500,0,9700
  -60,9420,-60,9500
  -60,9420,-60,9340
  -60,9340,-60,9280
  -60,9120,-60,9280
  -60,8940,-60,9120
  -60,8940,-60,8780
  -60,8780,0,8700
  0,8700,40,8680
  40,8680,240,8700
  240,8700,360,8780
  360,8780,640,8840
  1420,8400,1540,8480
  1540,8480,1680,8500
  1680,8500,1940,8460
  1180,8840,1280,8880
  1280,8880,1340,8860
  1340,8860,1720,8860
  1720,8860,1820,8920
  1820,8920,1820,9140
  1820,9140,1820,9280
  1820,9460,1820,9280
  1760,9480,1820,9460
  1640,9480,1760,9480
  1540,9500,1640,9480
  1340,9500,1540,9500
  1100,9500,1340,9500
  1040,9540,1100,9500
  960,9540,1040,9540
  300,9420,360,9460
  240,9440,300,9420
  180,9600,240,9440
  120,9660,180,9600
  100,9820,120,9660
  100,9820,120,9860
  120,9860,140,9900
  140,9900,140,10000
  140,10440,180,10540
  100,10080,140,10000
  100,10080,140,10100
  140,10100,140,10440
  180,10540,300,10560
  2140,9560,2140,9640
  2140,9720,2140,9640
  1880,9780,2140,9720
  1720,9780,1880,9780
  1620,9740,1720,9780
  1500,9780,1620,9740
  1380,9780,1500,9780
  1340,9820,1380,9780
  1200,9820,1340,9820
  1100,9780,1200,9820
  900,9780,1100,9780
  820,9720,900,9780
  540,9720,820,9720
  360,9840,540,9720
  360,9840,360,9960
  360,9960,360,10080
  360,10140,360,10080
  360,10140,360,10240
  360,10240,420,10320
  700,10300,820,10280
  820,10280,820,10280
  820,10280,900,10320
  900,10320,1040,10300
  1040,10300,1200,10320
  1200,10320,1380,10280
  1380,10280,1500,10300
  1500,10300,1760,10300
  2800,10620,2840,10600
  2840,10600,2900,10600
  2900,10600,3000,10620
  3000,10620,3080,10620
  3080,10620,3140,10600
  3140,10540,3140,10600
  3140,10540,3140,10460
  3140,10460,3140,10360
  3140,10360,3140,10260
  3140,10260,3140,10140
  3140,10140,3140,10000
  3140,10000,3140,9860
  3140,9860,3160,9720
  3160,9720,3160,9580
  3160,9580,3160,9440
  3160,9300,3160,9440
  3160,9300,3160,9140
  3160,9140,3160,8980
  3160,8980,3160,8820
  3160,8820,3160,8680
  3160,8680,3160,8520
  1760,10300,1880,10300
  660,9500,960,9540
  640,9460,660,9500
  360,9460,640,9460
  -480,10760,-440,10880
  -480,11020,-440,10880
  -480,11160,-260,11240
  -480,11020,-480,11160
  -600,11420,-380,11320
  -380,11320,-200,11340
  -200,11340,0,11340
  0,11340,180,11340
  960,13420,960,13300
  960,13420,960,13520
  960,13520,1000,13560
  1000,13560,1040,13540
  1040,13540,1200,13440
  1200,13440,1380,13380
  1380,13380,1620,13300
  1620,13300,1820,13220
  1820,13220,2000,13200
  2000,13200,2240,13200
  2240,13200,2440,13160
  2440,13160,2640,13040
  -480,10760,-440,10620
  -440,10620,-360,10560
  -380,10460,-360,10560
  -380,10460,-360,10300
  -380,10140,-360,10300
  -380,10140,-380,10040
  -380,9880,-380,10040
  -380,9720,-380,9880
  -380,9720,-380,9540
  -380,9360,-380,9540
  -380,9180,-380,9360
  -380,9180,-380,9000
  -380,8840,-380,9000
  -380,8840,-380,8760
  -380,8760,-380,8620
  -380,8620,-380,8520
  -380,8520,-360,8400
  -360,8400,-100,8400
  -100,8400,-60,8420
  -60,8420,240,8440
  240,8440,240,8380
  240,8380,500,8440
  500,8440,760,8460
  760,8460,1000,8400
  1000,8400,1180,8420
  1180,8420,1420,8400
  1940,8460,2140,8420
  2140,8420,2200,8520
  2200,8680,2200,8520
  2140,8840,2200,8680
  2140,8840,2140,9020
  2140,9100,2140,9020
  2140,9200,2140,9100
  2140,9200,2200,9320
  2200,9320,2200,9440
  2140,9560,2200,9440
  1880,10300,2200,10280
  2200,10280,2480,10260
  2480,10260,2700,10240
  2700,10240,2840,10180
  2840,10180,2900,10060
  2900,9860,2900,10060
  2900,9640,2900,9860
  2900,9640,2900,9500
  2900,9460,2900,9500
  2740,9460,2900,9460
  2700,9460,2740,9460
  2700,9360,2700,9460
  2700,9320,2700,9360
  2600,9320,2700,9320
  2600,9260,2600,9320
  2600,9200,2600,9260
  2480,9120,2600,9200
  2440,9080,2480,9120
  2380,9080,2440,9080
  2320,9060,2380,9080
  2320,8860,2320,9060
  2320,8860,2380,8840
  2380,8840,2480,8860
  2480,8860,2600,8840
  2600,8840,2740,8840
  2740,8840,2840,8800
  2840,8800,2900,8700
  2900,8600,2900,8700
  2900,8480,2900,8600
  2900,8380,2900,8480
  2900,8380,2900,8260
  2900,8260,2900,8140
  2900,8140,2900,8020
  2900,8020,2900,7900
  2900,7820,2900,7900
  2900,7820,2900,7740
  2900,7660,2900,7740
  2900,7560,2900,7660
  2900,7460,2900,7560
  2900,7460,2900,7360
  2900,7260,2900,7360
  2840,7160,2900,7260
  2800,7080,2840,7160
  2700,7100,2800,7080
  2560,7120,2700,7100
  2400,7100,2560,7120
  2320,7100,2400,7100
  2140,7100,2320,7100
  2040,7080,2140,7100
  1940,7080,2040,7080
  1820,7140,1940,7080
  1680,7140,1820,7140
  1540,7140,1680,7140
  1420,7220,1540,7140
  1280,7220,1380,7220
  1140,7200,1280,7220
  1000,7220,1140,7200
  760,7280,900,7320
  540,7220,760,7280
  300,7180,540,7220
  180,7120,180,7160
  40,7140,180,7120
  -60,7160,40,7140
  -200,7120,-60,7160
  180,7160,300,7180
  -260,7060,-200,7120
  -260,6980,-260,7060
  -260,6880,-260,6980
  -260,6880,-260,6820
  -260,6820,-200,6760
  -200,6760,-100,6740
  -100,6740,-60,6740
  -60,6740,40,6740
  40,6740,300,6800
  300,6800,420,6760
  420,6760,500,6740
  500,6740,540,6760
  540,6760,540,6760
  540,6760,640,6780
  640,6660,640,6780
  580,6580,640,6660
  580,6440,580,6580
  580,6440,640,6320
  640,6320,640,6180
  580,6080,640,6180
  580,6080,640,5960
  640,5960,640,5840
  640,5840,640,5700
  640,5700,660,5560
  660,5560,660,5440
  660,5440,660,5300
  660,5140,660,5300
  660,5140,660,5000
  660,5000,660,4880
  660,4880,820,4860
  820,4860,1000,4840
  1000,4840,1100,4860
  1100,4860,1280,4860
  1280,4860,1420,4840
  1420,4840,1580,4860
  1580,4860,1720,4820
  1720,4820,1880,4860
  1880,4860,2000,4840
  2000,4840,2140,4840
  2140,4840,2320,4860
  2320,4860,2440,4880
  2440,4880,2600,4880
  2600,4880,2800,4880
  2800,4880,2900,4880
  2900,4880,2900,4820
  2900,4740,2900,4820
  2800,4700,2900,4740
  2520,4680,2800,4700
  2240,4660,2520,4680
  1940,4620,2240,4660
  1820,4580,1940,4620
  1820,4500,1820,4580
  1820,4500,1880,4420
  1880,4420,2000,4420
  2000,4420,2200,4420
  2200,4420,2400,4440
  2400,4440,2600,4440
  2600,4440,2840,4440
  2840,4440,2900,4400
  2740,4260,2900,4280
  2600,4240,2740,4260
  2480,4280,2600,4240
  2320,4240,2480,4280
  2140,4220,2320,4240
  1940,4220,2140,4220
  1880,4160,1940,4220
  1880,4160,1880,4080
  1880,4080,2040,4040
  2040,4040,2240,4060
  2240,4060,2400,4040
  2400,4040,2600,4060
  2600,4060,2740,4020
  2740,4020,2840,3940
  2840,3780,2840,3940
  2740,3660,2840,3780
  2700,3680,2740,3660
  2520,3700,2700,3680
  2380,3700,2520,3700
  2200,3720,2380,3700
  2040,3720,2200,3720
  1880,3700,2040,3720
  1820,3680,1880,3700
  1760,3600,1820,3680
  1760,3600,1820,3480
  1820,3480,1880,3440
  1880,3440,1960,3460
  1960,3460,2140,3460
  2140,3460,2380,3460
  2380,3460,2640,3440
  2640,3440,2900,3380
  2840,3280,2900,3380
  2840,3280,2900,3200
  2900,3200,2900,3140
  2840,3020,2900,3140
  2800,2960,2840,3020
  2700,3000,2800,2960
  2600,2980,2700,3000
  2380,3000,2600,2980
  2140,3000,2380,3000
  1880,3000,2140,3000
  1720,3040,1880,3000
  1640,2960,1720,3040
  1500,2940,1640,2960
  1340,3000,1500,2940
  1240,3000,1340,3000
  1140,3020,1240,3000
  1040,3000,1140,3020
  960,2960,1040,3000
  900,2960,960,2960
  840,2840,900,2960
  700,2820,840,2840
  540,2820,700,2820
  420,2820,540,2820
  180,2800,420,2820
  60,2780,180,2800
  -60,2800,60,2780
  -160,2760,-60,2800
  -260,2740,-160,2760
  -300,2640,-260,2740
  -360,2560,-300,2640
  -380,2460,-360,2560
  -380,2460,-300,2380
  -300,2300,-300,2380
  -300,2300,-300,2220
  -300,2100,-300,2220
  -300,2100,-300,2040
  -300,2040,-160,2040
  -160,2040,-60,2040
  -60,2040,60,2040
  60,2040,180,2040
  180,2040,360,2040
  360,2040,540,2040
  540,2040,700,2080
  660,2160,700,2080
  660,2160,700,2260
  660,2380,700,2260
  500,2340,660,2380
  360,2340,500,2340
  240,2340,360,2340
  40,2320,240,2340
  -60,2320,40,2320
  -100,2380,-60,2320
  -100,2380,-100,2460
  -100,2460,-100,2540
  -100,2540,0,2560
  0,2560,140,2600
  140,2600,300,2600
  300,2600,460,2600
  460,2600,640,2600
  640,2600,760,2580
  760,2580,820,2560
  820,2560,820,2500
  820,2500,820,2400
  820,2400,840,2320
  840,2320,840,2240
  820,2120,840,2240
  820,2020,820,2120
  820,1900,820,2020
  760,1840,820,1900
  640,1840,760,1840
  500,1840,640,1840
  300,1860,420,1880
  180,1840,300,1860
  420,1880,500,1840
  0,1840,180,1840
  -60,1860,0,1840
  -160,1840,-60,1860
  -200,1800,-160,1840
  -260,1760,-200,1800
  -260,1680,-260,1760
  -260,1620,-260,1680
  -260,1540,-260,1620
  -260,1540,-260,1460
  -300,1420,-260,1460
  -300,1420,-300,1340
  -300,1340,-260,1260
  -260,1260,-260,1160
  -260,1060,-260,1160
  -260,1060,-260,960
  -260,880,-260,960
  -260,880,-260,780
  -260,780,-260,680
  -300,580,-260,680
  -300,580,-300,480
  -300,480,-260,400
  -300,320,-260,400
  -300,320,-300,240
  -300,240,-200,220
  -200,220,-200,160
  -200,160,-100,140
  -100,140,0,120
  0,120,60,120
  60,120,180,120
  180,120,300,120
  300,120,420,140
  420,140,580,180
  580,180,760,180
  760,180,900,180
  960,180,1100,180
  1100,180,1340,200
  1340,200,1580,200
  1580,200,1720,180
  1720,180,2000,140
  2000,140,2240,140
  2240,140,2480,140
  2520,140,2800,160
  2800,160,3000,160
  3000,160,3140,160
  3140,260,3140,160
  3140,260,3140,380
  3080,500,3140,380
  3080,620,3080,500
  3080,620,3080,740
  3080,740,3080,840
  3080,960,3080,840
  3080,1080,3080,960
  3080,1080,3080,1200
  3080,1200,3080,1340
  3080,1340,3080,1460
  3080,1580,3080,1460
  3080,1700,3080,1580
  3080,1700,3080,1760
  3080,1760,3200,1760
  3200,1760,3320,1760
  3320,1760,3520,1760
  3520,1760,3680,1740
  3680,1740,3780,1700
  3780,1700,3840,1620
  3840,1620,3840,1520
  3840,1520,3840,1420
  3840,1320,3840,1420
  3840,1120,3840,1320
  3840,1120,3840,940
  3840,940,3840,760
  3780,600,3840,760
  3780,600,3780,440
  3780,320,3780,440
  3780,320,3780,160
  3780,60,3780,160
  3780,60,4020,60
  4020,60,4260,40
  4260,40,4500,40
  4500,40,4740,40
  4740,40,4840,20
  4840,20,4880,80
  4880,80,5080,40
  5080,40,5280,20
  5280,20,5500,0
  5500,0,5720,0
  5720,0,5940,60
  5940,60,6240,60
  6240,60,6540,20
  6540,20,6840,20
  6840,20,7040,0
  7040,0,7140,0
  7140,0,7400,20
  7400,20,7680,0
  7680,0,7940,0
  7940,0,8200,-20
  8200,-20,8360,20
  8360,20,8560,-40
  8560,-40,8760,0
  8760,0,8880,40
  8880,120,8880,40
  8840,220,8840,120
  8620,240,8840,220
  8420,260,8620,240
  8200,280,8420,260
  7940,280,8200,280
  7760,240,7940,280
  7560,220,7760,240
  7360,280,7560,220
  7140,260,7360,280
  6940,240,7140,260
  6720,220,6940,240
  6480,220,6720,220
  6360,300,6480,220
  6240,300,6360,300
  6200,500,6240,300
  6200,500,6360,540
  6360,540,6540,520
  6540,520,6720,480
  6720,480,6880,460
  6880,460,7080,500
  7080,500,7320,500
  7320,500,7680,500
  7680,620,7680,500
  7520,640,7680,620
  7360,640,7520,640
  7200,640,7360,640
  7040,660,7200,640
  6880,720,7040,660
  6720,700,6880,720
  6540,700,6720,700
  6420,760,6540,700
  6280,740,6420,760
  6240,760,6280,740
  6200,920,6240,760
  6200,920,6360,960
  6360,960,6540,960
  6540,960,6720,960
  6720,960,6760,980
  6760,980,6880,940
  6880,940,7080,940
  7080,940,7280,940
  7280,940,7520,920
  7520,920,7760,900
  7760,900,7980,860
  7980,860,8100,880
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  4880,6980,5160,6980
  5160,6980,5400,7000
  5400,7000,5560,7020
  5560,7020,5660,7080
  5660,7080,5660,7280
  5660,7280,5660,7440
  5660,7440,5740,7520
  5740,7520,5740,7600
  5740,7600,5900,7600
  5900,7600,6040,7540
  6040,7540,6040,7320
  6040,7320,6120,7200
  6120,7200,6120,7040
  6120,7040,6240,7000
  6240,7000,6480,7060
  6480,7060,6800,7060
  6800,7060,7080,7080
  7080,7080,7320,7100
  7940,7100,7980,6920
  7860,6860,7980,6920
  7640,6860,7860,6860
  7400,6840,7640,6860
  7320,7100,7560,7120
  7560,7120,7760,7120
  7760,7120,7940,7100
  7200,6820,7400,6840
  7040,6820,7200,6820
  6600,6840,6840,6840
  6380,6800,6600,6840
  6120,6800,6380,6800
  5900,6840,6120,6800
  5620,6820,5900,6840
  5400,6800,5620,6820
  5140,6800,5400,6800
  4880,6780,5140,6800
  4600,6760,4880,6780
  4340,6760,4600,6760
  4080,6760,4340,6760
  3840,6740,4080,6760
  3680,6720,3840,6740
  3680,6720,3680,6560
  3680,6560,3720,6400
  3720,6400,3720,6200
  3720,6200,3780,6000
  3720,5780,3780,6000
  3720,5580,3720,5780
  3720,5360,3720,5580
  3720,5360,3840,5240
  3840,5240,4200,5260
  4200,5260,4600,5280
  4600,5280,4880,5280
  4880,5280,5140,5200
  5140,5200,5220,5100
  5220,5100,5280,4900
  5280,4900,5340,4840
  5340,4840,5720,4880
  6120,4880,6480,4860
  6880,4840,7200,4860
  6480,4860,6880,4840
  7200,4860,7320,4860
  7320,4860,7360,4740
  7360,4600,7440,4520
  7360,4600,7360,4740
  7440,4520,7640,4520
  7640,4520,7800,4480
  7800,4480,7800,4280
  7800,4280,7800,4040
  7800,4040,7800,3780
  7800,3560,7800,3780
  7800,3560,7860,3440
  7860,3440,8060,3460
  8060,3460,8160,3340
  8160,3340,8160,3140
  8160,3140,8160,2960
  8000,2900,8160,2960
  7860,2900,8000,2900
  7640,2940,7860,2900
  7400,2980,7640,2940
  7100,2980,7400,2980
  6840,3000,7100,2980
  5620,2980,5840,2980
  5840,2980,6500,3000
  6500,3000,6840,3000
  5560,2780,5620,2980
  5560,2780,5560,2580
  5560,2580,5560,2380
  5560,2140,5560,2380
  5560,2140,5560,1900
  5560,1900,5620,1660
  5620,1660,5660,1460
  5660,1460,5660,1300
  5500,1260,5660,1300
  5340,1260,5500,1260
  4600,1220,4840,1240
  4440,1220,4600,1220
  4440,1080,4440,1220
  4440,1080,4600,1020
  5080,1260,5340,1260
  4840,1240,5080,1260
  4600,1020,4940,1020
  4940,1020,5220,1020
  5220,1020,5560,960
  5560,960,5660,860
  5660,740,5660,860
  5280,740,5660,740
  4940,780,5280,740
  4660,760,4940,780
  4500,700,4660,760
  4500,520,4500,700
  4500,520,4700,460
  4700,460,5080,440
  5440,420,5740,420
  5080,440,5440,420
  5740,420,5840,360
  5800,280,5840,360
  5560,280,5800,280
  4980,300,5280,320
  4360,320,4660,300
  4200,360,4360,320
  5280,320,5560,280
  4660,300,4980,300
  4140,480,4200,360
  4140,480,4140,640
  4140,640,4200,780
  4200,780,4200,980
  4200,980,4220,1180
  4220,1400,4220,1180
  4220,1400,4260,1540
  4260,1540,4500,1540
  4500,1540,4700,1520
  4700,1520,4980,1540
  5280,1560,5400,1560
  4980,1540,5280,1560
  5400,1560,5400,1700
  5400,1780,5400,1700
  5340,1900,5400,1780
  5340,2020,5340,1900
  5340,2220,5340,2020
  5340,2220,5340,2420
  5340,2420,5340,2520
  5080,2600,5220,2580
  5220,2580,5340,2520
  4900,2580,5080,2600
  4700,2540,4900,2580
  4500,2540,4700,2540
  4220,2580,4340,2540
  4200,2700,4220,2580
  4340,2540,4500,2540
  3980,2740,4200,2700
  3840,2740,3980,2740
  3780,2640,3840,2740
  3780,2640,3780,2460
  3780,2280,3780,2460
  3620,2020,3780,2100
  3780,2280,3780,2100
  3360,2040,3620,2020
  3080,2040,3360,2040
  2840,2020,3080,2040
  2740,1940,2840,2020
  2740,1940,2800,1800
  2800,1640,2800,1800
  2800,1640,2800,1460
  2800,1300,2800,1460
  2700,1180,2800,1300
  2480,1140,2700,1180
  1580,1200,1720,1200
  2240,1180,2480,1140
  1960,1180,2240,1180
  1720,1200,1960,1180
  1500,1320,1580,1200
  1500,1440,1500,1320
  1500,1440,1760,1480
  1760,1480,1940,1480
  1940,1480,2140,1500
  2140,1500,2320,1520
  2400,1560,2400,1700
  2280,1820,2380,1780
  2320,1520,2400,1560
  2380,1780,2400,1700
  2080,1840,2280,1820
  1720,1820,2080,1840
  1420,1800,1720,1820
  1280,1800,1420,1800
  1240,1720,1280,1800
  1240,1720,1240,1600
  1240,1600,1280,1480
  1280,1340,1280,1480
  1180,1280,1280,1340
  1000,1280,1180,1280
  760,1280,1000,1280
  360,1240,540,1260
  180,1220,360,1240
  540,1260,760,1280
  180,1080,180,1220
  180,1080,180,1000
  180,1000,360,940
  360,940,540,960
  540,960,820,980
  1100,980,1200,920
  820,980,1100,980
  6640,11860,6940,11920
  5200,11280,5500,11280
  4120,7330,4120,7230
  4120,7230,4660,7250
  4660,7250,4940,7250
  4940,7250,5050,7340
  5010,7400,5050,7340
  4680,7380,5010,7400
  4380,7370,4680,7380
  4120,7330,4360,7370
  4120,7670,4120,7760
  4120,7670,4280,7650
  4280,7650,4540,7660
  4550,7660,4820,7680
  4820,7680,4900,7730
  4880,7800,4900,7730
  4620,7820,4880,7800
  4360,7790,4620,7820
  4120,7760,4360,7790
  6840,6840,7040,6820
  5720,4880,6120,4880
  1200,920,1340,810
  1340,810,1520,790
  1520,790,1770,800
  2400,790,2600,750
  2600,750,2640,520
  2520,470,2640,520
  2140,470,2520,470
  1760,800,2090,800
  2080,800,2400,790
  1760,450,2140,470
  1420,450,1760,450
  1180,440,1420,450
  900,480,1180,440
  640,450,900,480
  360,440,620,450
  120,430,360,440
  0,520,120,430
  -20,780,0,520
  -20,780,-20,1020
  -20,1020,-20,1150
  -20,1150,0,1300
  0,1470,60,1530
  0,1300,0,1470
  60,1530,360,1530
  360,1530,660,1520
  660,1520,980,1520
  980,1520,1040,1520
  1040,1520,1070,1560
  1070,1770,1070,1560
  1070,1770,1100,2010
  1070,2230,1100,2010
  1070,2240,1180,2340
  1180,2340,1580,2340
  1580,2340,1940,2350
  1940,2350,2440,2350
  2440,2350,2560,2380
  2560,2380,2600,2540
  2810,2640,3140,2680
  2600,2540,2810,2640
  3140,2680,3230,2780
  3230,2780,3260,2970
  3230,3220,3260,2970
  3200,3470,3230,3220
  3200,3480,3210,3760
  3210,3760,3210,4040
  3200,4040,3230,4310
  3210,4530,3230,4310
  3210,4530,3230,4730
  3230,4960,3230,4730
  3230,4960,3260,5190
  3170,5330,3260,5190
  2920,5330,3170,5330
  2660,5360,2920,5330
  2420,5330,2660,5360
  2200,5280,2400,5330
  2020,5280,2200,5280
  1840,5260,2020,5280
  1660,5280,1840,5260
  1500,5300,1660,5280
  1360,5270,1500,5300
  1200,5290,1340,5270
  1070,5400,1200,5290
  1040,5630,1070,5400
  1000,5900,1040,5630
  980,6170,1000,5900
  980,6280,980,6170
  980,6540,980,6280
  980,6540,1040,6720
  1040,6720,1360,6730
  1360,6730,1760,6710
  2110,6720,2420,6730
  1760,6710,2110,6720
  2420,6730,2640,6720
  2640,6720,2970,6720
  2970,6720,3160,6700
  3160,6700,3240,6710
  3240,6710,3260,6890
  3260,7020,3260,6890
  3230,7180,3260,7020
  3230,7350,3230,7180
  3210,7510,3230,7350
  3210,7510,3210,7690
  3210,7870,3210,7690
  3210,7870,3210,7980
  3200,8120,3210,7980
  3200,8330,3200,8120
  3160,8520,3200,8330
  2460,11100,2480,11020
  2200,11180,2460,11100
  1260,11350,1600,11320
  600,11430,930,11400
  180,11340,620,11430
  1600,11320,1910,11280
  1910,11280,2200,11180
  923.0029599285435,11398.99893503157,1264.002959928544,11351.99893503157
#+end_src

*** Platformer - The Little Probe - Data - level_lava.txt
#+begin_src ruby
  # ./samples/99_genre_platformer/the_little_probe/data/level_lava.txt
  100,10740,500,10780
  500,10780,960,10760
  960,10760,1340,10760
  1380,10760,1820,10780
  1820,10780,2240,10780
  2280,10780,2740,10740
  2740,10740,3000,10780
  3000,10780,3140,11020
  -520,8820,-480,9160
  -520,8480,-520,8820
  -520,8480,-480,8180
  -480,8180,-200,8120
  -200,8120,100,8220
  100,8220,420,8240
  420,8240,760,8260
  760,8260,1140,8280
  1140,8280,1500,8200
  1500,8200,1880,8240
  1880,8240,2240,8260
  2240,8260,2320,8480
  2320,8480,2380,8680
  2240,8860,2380,8680
  2240,9080,2240,8860
  2240,9080,2320,9260
  2320,9260,2480,9440
  2480,9440,2600,9640
  2480,9840,2600,9640
  2400,10020,2480,9840
  2240,10080,2400,10020
  1960,10080,2240,10080
  1720,10080,1960,10080
  1460,10080,1720,10080
  1180,10080,1420,10080
  900,10080,1180,10080
  640,10080,900,10080
  640,10080,640,9900
  60,10520,100,10740
  40,10240,60,10520
  40,10240,40,9960
  40,9960,40,9680
  40,9680,40,9360
  40,9360,60,9080
  60,9080,100,8860
  100,8860,460,9040
  460,9040,760,9220
  760,9220,1140,9220
  1140,9220,1720,9200
  -660,11580,-600,11420
  -660,11800,-660,11580
  -660,12000,-660,11800
  -660,12000,-600,12220
  -600,12220,-600,12440
  -600,12440,-600,12640
  -600,11240,-260,11280
  -260,11280,100,11240
  9000,12360,9020,12400
  9020,12620,9020,12400
  9020,12840,9020,12620
  9020,13060,9020,12840
  9020,13060,9020,13240
  9020,13240,9020,13420
  9020,13420,9020,13600
  9020,13600,9020,13780
  8880,13900,9020,13780
  8560,13800,8880,13900
  8220,13780,8560,13800
  7860,13760,8220,13780
  7640,13780,7860,13760
  7360,13800,7640,13780
  7100,13800,7360,13800
  6540,13760,6800,13780
  6800,13780,7100,13800
  6280,13760,6540,13760
  5760,13760,6280,13760
  5220,13780,5760,13760
  4700,13760,5220,13780
  4200,13740,4700,13760
  3680,13720,4200,13740
  3140,13700,3680,13720
  2600,13680,3140,13700
  2040,13940,2600,13680
  1640,13940,2040,13940
  1200,13960,1640,13940
  840,14000,1200,13960
  300,13960,840,14000
  -200,13900,300,13960
  -600,12840,-600,12640
  -600,13140,-600,12840
  -600,13140,-600,13420
  -600,13700,-600,13420
  -600,13700,-600,13820
  -600,13820,-200,13900
  -600,11240,-560,11000
  -560,11000,-480,10840
  -520,10660,-480,10840
  -520,10660,-520,10480
  -520,10480,-520,10300
  -520,10260,-480,10080
  -480,9880,-440,10060
  -520,9680,-480,9880
  -520,9680,-480,9400
  -480,9400,-480,9160
  1820,9880,2140,9800
  1540,9880,1820,9880
  1200,9920,1500,9880
  900,9880,1200,9920
  640,9900,840,9880
  2380,8760,2800,8760
  2800,8760,2840,8660
  2840,8660,2840,8420
  2840,8160,2840,8420
  2800,7900,2840,8160
  2800,7900,2800,7720
  2800,7540,2800,7720
  2800,7540,2800,7360
  2700,7220,2800,7360
  2400,7220,2700,7220
  2080,7240,2400,7220
  1760,7320,2080,7240
  1380,7360,1720,7320
  1040,7400,1340,7360
  640,7400,1000,7420
  300,7380,640,7400
  0,7300,240,7380
  -300,7180,-60,7300
  -380,6860,-360,7180
  -380,6880,-360,6700
  -360,6700,-260,6540
  -260,6540,0,6520
  0,6520,240,6640
  240,6640,460,6640
  460,6640,500,6480
  500,6260,500,6480
  460,6060,500,6260
  460,5860,460,6060
  460,5860,500,5640
  500,5640,540,5440
  540,5440,580,5220
  580,5220,580,5000
  580,4960,580,4740
  580,4740,960,4700
  960,4700,1140,4760
  1140,4760,1420,4740
  1420,4740,1720,4700
  1720,4700,2000,4740
  2000,4740,2380,4760
  2380,4760,2700,4800
  1720,4600,1760,4300
  1760,4300,2200,4340
  2200,4340,2560,4340
  2560,4340,2740,4340
  2160,12580,2440,12400
  1820,12840,2160,12580
  1500,13080,1820,12840
  1140,13340,1500,13080
  1140,13340,1580,13220
  2110,13080,2520,13000
  2520,13000,2900,12800
  1580,13220,2110,13080
  2900,12800,3200,12680
  3200,12680,3440,12640
  3440,12640,3720,12460
  3720,12460,4040,12320
  4040,12320,4360,12200
  4360,11940,4380,12180
  4360,11700,4360,11940
  4360,11700,4540,11500
  4540,11500,4880,11540
  6000,11660,6280,11640
  5440,11600,5720,11610
  5720,11610,6000,11660
  6280,11640,6760,11720
  6760,11720,7060,11780
  7060,11780,7360,11810
  7360,11810,7640,11840
  7640,11840,8000,11830
  8000,11830,8320,11850
  8320,11850,8390,11800
  8330,11760,8390,11800
  8160,11760,8330,11760
  7910,11750,8160,11760
  7660,11740,7900,11750
  7400,11730,7660,11740
  7160,11680,7400,11730
  7080,11570,7160,11680
  7080,11570,7100,11350
  7100,11350,7440,11280
  7440,11280,7940,11280
  7960,11280,8360,11280
  5840,11540,6650,11170
  4880,11540,5440,11600
  3410,11830,3420,11300
  3410,11260,3520,10920
  3520,10590,3520,10920
  3520,10590,3540,10260
  3520,9900,3540,10240
  3520,9900,3640,9590
  3640,9570,4120,9590
  4140,9590,4600,9680
  4620,9680,5030,9730
  5120,9750,5520,9800
  5620,9820,6080,9800
  6130,9810,6580,9820
  6640,9820,6800,9700
  6780,9400,6800,9700
  6780,9400,6840,9140
  6820,8860,6840,9120
  6780,8600,6820,8830
  6720,8350,6780,8570
  6480,8340,6720,8320
  6260,8400,6480,8340
  6050,8580,6240,8400
  5760,8630,6040,8590
  5520,8690,5740,8630
  5120,8690,5450,8700
  4570,8670,5080,8690
  4020,8610,4540,8670
  3540,8480,4020,8610
  3520,8230,3520,8480
  3520,7930,3520,8230
  3520,7930,3540,7630
  3480,7320,3540,7610
  3480,7280,3500,7010
  3500,6980,3680,6850
  3680,6850,4220,6840
  4230,6840,4760,6850
  4780,6850,5310,6860
  5310,6860,5720,6940
  5720,6940,5880,7250
  5880,7250,5900,7520
  100,11240,440,11300
  440,11300,760,11330
  1480,11280,1840,11230
  2200,11130,2360,11090
  1840,11230,2200,11130
#+end_src

*** Rpg Narrative - Choose Your Own Adventure - decision.rb
#+begin_src ruby
  # ./samples/99_genre_rpg_narrative/choose_your_own_adventure/app/decision.rb
  # Hey there! Welcome to Four Decisions. Here is how you
  # create your decision tree. Remove =being and =end from the text to
  # enable the game (just save the file). Change stuff and see what happens!
  
  def game
    {
      starting_decision: :stormy_night,
      decisions: {
        stormy_night: {
          description: 'It was a dark and stormy night. (storyline located in decision.rb)',
          option_one: {
            description: 'Go to sleep.',
            decision: :nap
          },
          option_two: {
            description: 'Watch a movie.',
            decision: :movie
          },
          option_three: {
            description: 'Go outside.',
            decision: :go_outside
          },
          option_four: {
            description: 'Get a snack.',
            decision: :get_a_snack
          }
        },
        nap: {
          description: 'You took a nap. The end.',
          option_one: {
            description: 'Start over.',
            decision: :stormy_night
          }
        }
      }
    }
  end

#+end_src

*** Rpg Narrative - Choose Your Own Adventure - main.rb
#+begin_src ruby
  # ./samples/99_genre_rpg_narrative/choose_your_own_adventure/app/main.rb
  =begin
  
   Reminders:
  
   - Hashes: Collection of unique keys and their corresponding values. The values can be found
     using their keys.
  
     In this sample app, the decisions needed for the game are stored in a hash. In fact, the
     decision.rb file contains hashes inside of other hashes!
  
     Each option is a key in the first hash, but also contains a hash (description and
     decision being its keys) as its value.
     Go into the decision.rb file and take a look before diving into the code below.
  
   - args.outputs.labels: An array. The values generate a label.
     The parameters are [X, Y, TEXT, SIZE, ALIGNMENT, RED, GREEN, BLUE, ALPHA, FONT STYLE]
     For more information about labels, go to mygame/documentation/02-labels.md.
  
   - args.keyboard.key_down.KEY: Determines if a key is in the down state or pressed down.
     For more information about the keyboard, go to mygame/documentation/06-keyboard.md.
  
   - String interpolation: uses #{} syntax; everything between the #{ and the } is evaluated
     as Ruby code, and the placeholder is replaced with its corresponding value or result.
  
  =end
  
  # This sample app provides users with a story and multiple decisions that they can choose to make.
  # Users can make a decision using their keyboard, and the story will move forward based on user choices.
  
  # The decisions available to users are stored in the decision.rb file.
  # We must have access to it for the game to function properly.
  GAME_FILE = 'app/decision.rb' # found in app folder
  
  require GAME_FILE # require used to load another file, import class/method definitions
  
  # Instructions are given using labels to users if they have not yet set up their story in the decision.rb file.
  # Otherwise, the game is run.
  def tick args
    if !args.state.loaded && !respond_to?(:game) # if game is not loaded and not responding to game symbol's method
      args.labels << [640, 370, 'Hey there! Welcome to Four Decisions.', 0, 1] # a welcome label is shown
      args.labels << [640, 340, 'Go to the file called decision.rb and tell me your story.', 0, 1]
    elsif respond_to?(:game) # otherwise, if responds to game
      args.state.loaded = true
      tick_game args # calls tick_game method, runs game
    end
  
    if args.state.tick_count.mod_zero? 60 # update every 60 frames
      t = args.gtk.ffi_file.mtime GAME_FILE # mtime returns modification time for named file
      if t != args.state.mtime
        args.state.mtime = t
        require GAME_FILE # require used to load file
        args.state.game_definition = nil # game definition and decision are empty
        args.state.decision_id = nil
      end
    end
  end
  
  # Runs methods needed for game to function properly
  # Creates a rectangular border around the screen
  def tick_game args
    defaults args
    args.borders << args.grid.rect
    render_decision args
    process_inputs args
  end
  
  # Sets default values and uses decision.rb file to define game and decision_id
  # variable using the starting decision
  def defaults args
    args.state.game_definition ||= game
    args.state.decision_id ||= args.state.game_definition[:starting_decision]
  end
  
  # Outputs the possible decision descriptions the user can choose onto the screen
  # as well as what key to press on their keyboard to make their decision
  def render_decision args
    decision = current_decision args
    # text is either the value of decision's description key or warning that no description exists
    args.labels << [640, 360, decision[:description] || "No definition found for #{args.state.decision_id}. Please update decision.rb.", 0, 1] # uses string interpolation
  
    # All decisions are stored in a hash
    # The descriptions output onto the screen are the values for the description keys of the hash.
    if decision[:option_one]
      args.labels << [10, 360, decision[:option_one][:description], 0, 0] # option one's description label
      args.labels << [10, 335, "(Press 'left' on the keyboard to select this decision)", -5, 0] # label of what key to press to select the decision
    end
  
    if decision[:option_two]
      args.labels << [1270, 360, decision[:option_two][:description], 0, 2] # option two's description
      args.labels << [1270, 335, "(Press 'right' on the keyboard to select this decision)", -5, 2]
    end
  
    if decision[:option_three]
      args.labels << [640, 45, decision[:option_three][:description], 0, 1] # option three's description
      args.labels << [640, 20, "(Press 'down' on the keyboard to select this decision)", -5, 1]
    end
  
    if decision[:option_four]
      args.labels << [640, 700, decision[:option_four][:description], 0, 1] # option four's description
      args.labels << [640, 675, "(Press 'up' on the keyboard to select this decision)", -5, 1]
    end
  end
  
  # Uses keyboard input from the user to make a decision
  # Assigns the decision as the value of the decision_id variable
  def process_inputs args
    decision = current_decision args # calls current_decision method
  
    if args.keyboard.key_down.left! && decision[:option_one] # if left key pressed and option one exists
      args.state.decision_id = decision[:option_one][:decision] # value of option one's decision hash key is set to decision_id
    end
  
    if args.keyboard.key_down.right! && decision[:option_two] # if right key pressed and option two exists
      args.state.decision_id = decision[:option_two][:decision] # value of option two's decision hash key is set to decision_id
    end
  
    if args.keyboard.key_down.down! && decision[:option_three] # if down key pressed and option three exists
      args.state.decision_id = decision[:option_three][:decision] # value of option three's decision hash key is set to decision_id
    end
  
    if args.keyboard.key_down.up! && decision[:option_four] # if up key pressed and option four exists
      args.state.decision_id = decision[:option_four][:decision] # value of option four's decision hash key is set to decision_id
    end
  end
  
  # Uses decision_id's value to keep track of current decision being made
  def current_decision args
    args.state.game_definition[:decisions][args.state.decision_id] || {} # either has value or is empty
  end
  
  # Resets the game.
  $gtk.reset

#+end_src

*** Rpg Narrative - Return Of Serenity - lowrez_simulator.rb
#+begin_src ruby
  # ./samples/99_genre_rpg_narrative/return_of_serenity/app/lowrez_simulator.rb
  ###################################################################################
  # YOU CAN PLAY AROUND WITH THE CODE BELOW, BUT USE CAUTION AS THIS IS WHAT EMULATES
  # THE 64x64 CANVAS.
  ###################################################################################
  
  TINY_RESOLUTION       = 64
  TINY_SCALE            = 720.fdiv(TINY_RESOLUTION + 5)
  CENTER_OFFSET         = 10
  EMULATED_FONT_SIZE    = 20
  EMULATED_FONT_X_ZERO  = 0
  EMULATED_FONT_Y_ZERO  = 46
  
  def tick args
    sprites = []
    labels = []
    borders = []
    solids = []
    mouse = emulate_lowrez_mouse args
    args.state.show_gridlines = false
    lowrez_tick args, sprites, labels, borders, solids, mouse
    render_gridlines_if_needed args
    render_mouse_crosshairs args, mouse
    emulate_lowrez_scene args, sprites, labels, borders, solids, mouse
  end
  
  def emulate_lowrez_mouse args
    args.state.new_entity_strict(:lowrez_mouse) do |m|
      m.x = args.mouse.x.idiv(TINY_SCALE) - CENTER_OFFSET.idiv(TINY_SCALE) - 1
      m.y = args.mouse.y.idiv(TINY_SCALE)
      if args.mouse.click
        m.click = [
          args.mouse.click.point.x.idiv(TINY_SCALE) - CENTER_OFFSET.idiv(TINY_SCALE) - 1,
          args.mouse.click.point.y.idiv(TINY_SCALE)
        ]
        m.down = m.click
      else
        m.click = nil
        m.down = nil
      end
  
      if args.mouse.up
        m.up = [
          args.mouse.up.point.x.idiv(TINY_SCALE) - CENTER_OFFSET.idiv(TINY_SCALE) - 1,
          args.mouse.up.point.y.idiv(TINY_SCALE)
        ]
      else
        m.up = nil
      end
    end
  end
  
  def render_mouse_crosshairs args, mouse
    return unless args.state.show_gridlines
    args.labels << [10, 25, "mouse: #{mouse.x} #{mouse.y}", 255, 255, 255]
  end
  
  def emulate_lowrez_scene args, sprites, labels, borders, solids, mouse
    args.render_target(:lowrez).solids  << [0, 0, 1280, 720]
    args.render_target(:lowrez).sprites << sprites
    args.render_target(:lowrez).borders << borders
    args.render_target(:lowrez).solids  << solids
    args.outputs.primitives << labels.map do |l|
      as_label = l.label
      l.text.each_char.each_with_index.map do |char, i|
        [CENTER_OFFSET + EMULATED_FONT_X_ZERO + (as_label.x * TINY_SCALE) + i * 5 * TINY_SCALE,
         EMULATED_FONT_Y_ZERO + (as_label.y * TINY_SCALE), char,
         EMULATED_FONT_SIZE, 0, as_label.r, as_label.g, as_label.b, as_label.a, 'fonts/dragonruby-gtk-4x4.ttf'].label
      end
    end
  
    args.sprites    << [CENTER_OFFSET, 0, 1280 * TINY_SCALE, 720 * TINY_SCALE, :lowrez]
  end
  
  def render_gridlines_if_needed args
    if args.state.show_gridlines && args.static_lines.length == 0
      args.static_lines << 65.times.map do |i|
        [
          [CENTER_OFFSET + i * TINY_SCALE + 1,  0,
           CENTER_OFFSET + i * TINY_SCALE + 1,  720,                128, 128, 128],
          [CENTER_OFFSET + i * TINY_SCALE,      0,
           CENTER_OFFSET + i * TINY_SCALE,      720,                128, 128, 128],
          [CENTER_OFFSET,                       0 + i * TINY_SCALE,
           CENTER_OFFSET + 720,                 0 + i * TINY_SCALE, 128, 128, 128],
          [CENTER_OFFSET,                       1 + i * TINY_SCALE,
           CENTER_OFFSET + 720,                 1 + i * TINY_SCALE, 128, 128, 128]
        ]
      end
    elsif !args.state.show_gridlines
      args.static_lines.clear
    end
  end

#+end_src

*** Rpg Narrative - Return Of Serenity - main.rb
#+begin_src ruby
  # ./samples/99_genre_rpg_narrative/return_of_serenity/app/main.rb
  require 'app/require.rb'
  
  def defaults args
    args.outputs.background_color = [0, 0, 0]
    args.state.last_story_line_text ||= ""
    args.state.scene_history ||= []
    args.state.storyline_history ||= []
    args.state.word_delay ||= 8
    if args.state.tick_count == 0
      args.gtk.stop_music
      args.outputs.sounds << 'sounds/static-loop.ogg'
    end
  
    if args.state.last_story_line_text
      lines = args.state
                  .last_story_line_text
                  .gsub("-", "")
                  .gsub("~", "")
                  .wrapped_lines(50)
  
      args.outputs.labels << lines.map_with_index { |l, i| [690, 200 - (i * 25), l, 1, 0, 255, 255, 255] }
    elsif args.state.storyline_history[-1]
      lines = args.state
                  .storyline_history[-1]
                  .gsub("-", "")
                  .gsub("~", "")
                  .wrapped_lines(50)
  
      args.outputs.labels << lines.map_with_index { |l, i| [690, 200 - (i * 25), l, 1, 0, 255, 255, 255] }
    end
  
    return if args.state.current_scene
    set_scene(args, day_one_beginning(args))
  end
  
  def inputs_move_player args
    if args.state.scene_changed_at.elapsed_time > 5
      if args.keyboard.down  || args.keyboard.s || args.keyboard.j
        args.state.player.y -= 0.25
      elsif args.keyboard.up || args.keyboard.w || args.keyboard.k
        args.state.player.y += 0.25
      end
  
      if args.keyboard.left     || args.keyboard.a  || args.keyboard.h
        args.state.player.x -= 0.25
      elsif args.keyboard.right || args.keyboard.d  || args.keyboard.l
        args.state.player.x += 0.25
      end
  
      args.state.player.y = 60 if args.state.player.y > 63
      args.state.player.y =  0 if args.state.player.y < -3
      args.state.player.x = 60 if args.state.player.x > 63
      args.state.player.x =  0 if args.state.player.x < -3
    end
  end
  
  def null_or_empty? ary
    return true unless ary
    return true if ary.length == 0
    return false
  end
  
  def calc_storyline_hotspot args
    hotspots = args.state.storylines.find_all do |hs|
      args.state.player.inside_rect?(hs.shift_rect(-2, 0))
    end
  
    if !null_or_empty?(hotspots) && !args.state.inside_storyline_hotspot
      _, _, _, _, storyline = hotspots.first
      queue_storyline_text(args, storyline)
      args.state.inside_storyline_hotspot = true
    elsif null_or_empty?(hotspots)
      args.state.inside_storyline_hotspot = false
  
      args.state.storyline_queue_empty_at ||= args.state.tick_count
      args.state.is_storyline_dialog_active = false
      args.state.scene_storyline_queue.clear
    end
  end
  
  def calc_scenes args
    hotspots = args.state.scenes.find_all do |hs|
      args.state.player.inside_rect?(hs.shift_rect(-2, 0))
    end
  
    if !null_or_empty?(hotspots) && !args.state.inside_scene_hotspot
      _, _, _, _, scene_method_or_hash = hotspots.first
      if scene_method_or_hash.is_a? Symbol
        set_scene(args, send(scene_method_or_hash, args))
        args.state.last_hotspot_scene = scene_method_or_hash
        args.state.scene_history << scene_method_or_hash
      else
        set_scene(args, scene_method_or_hash)
      end
      args.state.inside_scene_hotspot = true
    elsif null_or_empty?(hotspots)
      args.state.inside_scene_hotspot = false
    end
  end
  
  def null_or_whitespace? word
    return true if !word
    return true if word.strip.length == 0
    return false
  end
  
  def calc_storyline_presentation args
    return unless args.state.tick_count > args.state.next_storyline
    return unless args.state.scene_storyline_queue
    next_storyline = args.state.scene_storyline_queue.shift
    if null_or_whitespace? next_storyline
      args.state.storyline_queue_empty_at ||= args.state.tick_count
      args.state.is_storyline_dialog_active = false
      return
    end
    args.state.storyline_to_show = next_storyline
    args.state.is_storyline_dialog_active = true
    args.state.storyline_queue_empty_at = nil
    if next_storyline.end_with?(".") || next_storyline.end_with?("!") || next_storyline.end_with?("?") || next_storyline.end_with?("\"")
      args.state.next_storyline += 60
    elsif next_storyline.end_with?(",")
      args.state.next_storyline += 50
    elsif next_storyline.end_with?(":")
      args.state.next_storyline += 60
    else
      default_word_delay = 13 + args.state.word_delay - 8
      if next_storyline.gsub("-", "").gsub("~", "").length <= 4
        default_word_delay = 11 + args.state.word_delay - 8
      end
      number_of_syllabals = next_storyline.length - next_storyline.gsub("-", "").length
      args.state.next_storyline += default_word_delay + number_of_syllabals * (args.state.word_delay + 1)
    end
  end
  
  def inputs_reload_current_scene args
    return
    if args.inputs.keyboard.key_down.r!
      reload_current_scene
    end
  end
  
  def inputs_dismiss_current_storyline args
    if args.inputs.keyboard.key_down.x!
      args.state.scene_storyline_queue.clear
    end
  end
  
  def inputs_restart_game args
    if args.inputs.keyboard.exclamation_point
      args.gtk.reset_state
    end
  end
  
  def inputs_change_word_delay args
    if args.inputs.keyboard.key_down.plus || args.inputs.keyboard.key_down.equal_sign
      args.state.word_delay -= 2
      if args.state.word_delay < 0
        args.state.word_delay = 0
        # queue_storyline_text args, "Text speed at MAXIMUM. Geez, how fast do you read?"
      else
        # queue_storyline_text args, "Text speed INCREASED."
      end
    end
  
    if args.inputs.keyboard.key_down.hyphen || args.inputs.keyboard.key_down.underscore
      args.state.word_delay += 2
      # queue_storyline_text args, "Text speed DECREASED."
    end
  end
  
  def multiple_lines args, x, y, texts, size = 0, minimum_alpha = nil
    texts.each_with_index.map do |t, i|
      [x, y - i * (25 + size * 2), t, size, 0, 255, 255, 255, adornments_alpha(args, 255, minimum_alpha)]
    end
  end
  
  def lowrez_tick args, lowrez_sprites, lowrez_labels, lowrez_borders, lowrez_solids, lowrez_mouse
    # args.state.show_gridlines = true
    defaults args
    render_current_scene args, lowrez_sprites, lowrez_labels, lowrez_solids
    render_controller args, lowrez_borders
    lowrez_solids << [0, 0, 64, 64, 0, 0, 0]
    calc_storyline_presentation args
    calc_scenes args
    calc_storyline_hotspot args
    inputs_move_player args
    inputs_print_mouse_rect args, lowrez_mouse
    inputs_reload_current_scene args
    inputs_dismiss_current_storyline args
    inputs_change_word_delay args
    inputs_restart_game args
  end
  
  def render_controller args, lowrez_borders
    args.state.up_button    = [85, 40, 15, 15, 255, 255, 255]
    args.state.down_button  = [85, 20, 15, 15, 255, 255, 255]
    args.state.left_button  = [65, 20, 15, 15, 255, 255, 255]
    args.state.right_button = [105, 20, 15, 15, 255, 255, 255]
    lowrez_borders << args.state.up_button
    lowrez_borders << args.state.down_button
    lowrez_borders << args.state.left_button
    lowrez_borders << args.state.right_button
  end
  
  def inputs_print_mouse_rect args, lowrez_mouse
    if lowrez_mouse.up
      args.state.mouse_held = false
    elsif lowrez_mouse.click
      mouse_rect = [lowrez_mouse.x, lowrez_mouse.y, 1, 1]
      if args.state.up_button.intersect_rect? mouse_rect
        args.state.player.y += 1
      end
  
      if args.state.down_button.intersect_rect? mouse_rect
        args.state.player.y -= 1
      end
  
      if args.state.left_button.intersect_rect? mouse_rect
        args.state.player.x -= 1
      end
  
      if args.state.right_button.intersect_rect? mouse_rect
        args.state.player.x += 1
      end
      args.state.mouse_held = true
    elsif args.state.mouse_held
      mouse_rect = [lowrez_mouse.x, lowrez_mouse.y, 1, 1]
      if args.state.up_button.intersect_rect? mouse_rect
        args.state.player.y += 0.25
      end
  
      if args.state.down_button.intersect_rect? mouse_rect
        args.state.player.y -= 0.25
      end
  
      if args.state.left_button.intersect_rect? mouse_rect
        args.state.player.x -= 0.25
      end
  
      if args.state.right_button.intersect_rect? mouse_rect
        args.state.player.x += 0.25
      end
    end
  
    if lowrez_mouse.click
      dx = lowrez_mouse.click.x - args.state.previous_mouse_click.x
      dy = lowrez_mouse.click.y - args.state.previous_mouse_click.y
      x, y, w, h = args.state.previous_mouse_click.x, args.state.previous_mouse_click.y, dx, dy
      puts "x #{lowrez_mouse.click.x}, y: #{lowrez_mouse.click.y}"
      if args.state.previous_mouse_click
  
        if dx < 0 && dx < 0
          x = x + w
          w = w.abs
          y = y + h
          h = h.abs
        end
  
        w += 1
        h += 1
  
        args.state.previous_mouse_click = nil
      else
        args.state.previous_mouse_click = lowrez_mouse.click
        square_x, square_y = lowrez_mouse.click
      end
    end
  end
  
  def try_centering! word
    word ||= ""
    just_word = word.gsub("-", "").gsub(",", "").gsub(".", "").gsub("'", "").gsub('""', "\"-\"")
    return word if just_word.strip.length == 0
    return word if just_word.include? "~"
    return "~#{word}" if just_word.length <= 2
    if just_word.length.mod_zero? 2
      center_index = just_word.length.idiv(2) - 1
    else
      center_index = (just_word.length - 1).idiv(2)
    end
    return "#{word[0..center_index - 1]}~#{word[center_index]}#{word[center_index + 1..-1]}"
  end
  
  def queue_storyline args, scene
    queue_storyline_text args, scene[:storyline]
  end
  
  def queue_storyline_text args, text
    args.state.last_story_line_text = text
    args.state.storyline_history << text if text
    words = (text || "").split(" ")
    words = words.map { |w| try_centering! w }
    args.state.scene_storyline_queue = words
    if args.state.scene_storyline_queue.length != 0
      args.state.scene_storyline_queue.unshift "~$--"
      args.state.storyline_to_show = "~."
    else
      args.state.storyline_to_show = ""
    end
    args.state.scene_storyline_queue << ""
    args.state.next_storyline = args.state.tick_count
  end
  
  def set_scene args, scene
    args.state.current_scene = scene
    args.state.background = scene[:background] ||  'sprites/todo.png'
    args.state.scene_fade = scene[:fade] || 0
    args.state.scenes = (scene[:scenes] || []).reject { |s| !s }
    args.state.scene_render_override = scene[:render_override]
    args.state.storylines = (scene[:storylines] || []).reject { |s| !s }
    args.state.scene_changed_at = args.state.tick_count
    if scene[:player]
      args.state.player = scene[:player]
    end
    args.state.inside_scene_hotspot = false
    args.state.inside_storyline_hotspot = false
    queue_storyline args, scene
  end
  
  def replay_storyline_rect
    [26, -1, 7, 4]
  end
  
  def labels_for_word word
    left_side_of_word = ""
    center_letter = ""
    right_side_of_word = ""
  
    if word[0] == "~"
      left_side_of_word = ""
      center_letter = word[1]
      right_side_of_word = word[2..-1]
    elsif word.length > 0
      left_side_of_word, right_side_of_word = word.split("~")
      center_letter = right_side_of_word[0]
      right_side_of_word = right_side_of_word[1..-1]
    end
  
    right_side_of_word = right_side_of_word.gsub("-", "")
  
    {
      left:   [29 - left_side_of_word.length * 4 - 1 * left_side_of_word.length, 2, left_side_of_word],
      center: [29, 2, center_letter, 255, 0, 0],
      right:  [34, 2, right_side_of_word]
    }
  end
  
  def render_scenes args, lowrez_sprites
    lowrez_sprites << args.state.scenes.flat_map do |hs|
      hotspot_square args, hs.x, hs.y, hs.w, hs.h
    end
  end
  
  def render_storylines args, lowrez_sprites
    lowrez_sprites << args.state.storylines.flat_map do |hs|
      hotspot_square args, hs.x, hs.y, hs.w, hs.h
    end
  end
  
  def adornments_alpha args, target_alpha = nil, minimum_alpha = nil
    return (minimum_alpha || 80) unless args.state.storyline_queue_empty_at
    target_alpha ||= 255
    target_alpha * args.state.storyline_queue_empty_at.ease(60)
  end
  
  def hotspot_square args, x, y, w, h
    if w >= 3 && h >= 3
      [
        [x + w.idiv(2) + 1, y, w.idiv(2), h, 'sprites/label-background.png', 0, adornments_alpha(args, 50), 23, 23, 23],
        [x, y, w.idiv(2), h, 'sprites/label-background.png', 0, adornments_alpha(args, 100), 223, 223, 223],
        [x + 1, y + 1, w - 2, h - 2, 'sprites/label-background.png', 0, adornments_alpha(args, 200), 40, 140, 40],
      ]
    else
      [
        [x, y, w, h, 'sprites/label-background.png', 0, adornments_alpha(args, 200), 0, 140, 0],
      ]
    end
  end
  
  def render_storyline_dialog args, lowrez_labels, lowrez_sprites
    return unless args.state.is_storyline_dialog_active
    return unless args.state.storyline_to_show
    labels = labels_for_word args.state.storyline_to_show
    if true # high rez version
      scale = 8.88
      offset = 45
      size = 25
      args.outputs.labels << [offset + labels[:left].x.-(1) * scale,
                              labels[:left].y * TINY_SCALE + 55,
                              labels[:left].text, size, 0, 0, 0, 0, 255,
                              'fonts/manaspc.ttf']
      center_text = labels[:center].text
      center_text = "|" if center_text == "$"
      args.outputs.labels << [offset + labels[:center].x * scale,
                              labels[:center].y * TINY_SCALE + 55,
                              center_text, size, 0, 255, 0, 0, 255,
                              'fonts/manaspc.ttf']
      args.outputs.labels << [offset + labels[:right].x * scale,
                              labels[:right].y * TINY_SCALE + 55,
                              labels[:right].text, size, 0, 0, 0, 0, 255,
                              'fonts/manaspc.ttf']
    else
      lowrez_labels << labels[:left]
      lowrez_labels << labels[:center]
      lowrez_labels << labels[:right]
    end
    args.state.is_storyline_dialog_active = true
    render_player args, lowrez_sprites
    lowrez_sprites <<  [0, 0, 64, 8, 'sprites/label-background.png']
  end
  
  def render_player args, lowrez_sprites
    lowrez_sprites << player_md_down(args, *args.state.player)
  end
  
  def render_adornments args, lowrez_sprites
    render_scenes args, lowrez_sprites
    render_storylines args, lowrez_sprites
    return if args.state.is_storyline_dialog_active
    lowrez_sprites << player_md_down(args, *args.state.player)
  end
  
  def global_alpha_percentage args, max_alpha = 255
    return 255 unless args.state.scene_changed_at
    return 255 unless args.state.scene_fade
    return 255 unless args.state.scene_fade > 0
    return max_alpha * args.state.scene_changed_at.ease(args.state.scene_fade)
  end
  
  def render_current_scene args, lowrez_sprites, lowrez_labels, lowrez_solids
    lowrez_sprites << [0, 0, 64, 64, args.state.background, 0, (global_alpha_percentage args)]
    if args.state.scene_render_override
      send args.state.scene_render_override, args, lowrez_sprites, lowrez_labels, lowrez_solids
    end
    storyline_to_show = args.state.storyline_to_show || ""
    render_adornments args, lowrez_sprites
    render_storyline_dialog args, lowrez_labels, lowrez_sprites
  
    if args.state.background == 'sprites/tribute-game-over.png'
      lowrez_sprites << [0, 0, 64, 11, 'sprites/label-background.png', 0, adornments_alpha(args, 200), 0, 0, 0]
      lowrez_labels << [9, 6, 'Return of', 255, 255, 255]
      lowrez_labels << [9, 1, ' Serenity', 255, 255, 255]
      if !args.state.ended
        args.gtk.stop_music
        args.outputs.sounds << 'sounds/music-loop.ogg'
        args.state.ended = true
      end
    end
  end
  
  def player_md_right args, x, y
    [x, y, 4, 11, 'sprites/player-right.png', 0, (global_alpha_percentage args)]
  end
  
  def player_md_left args, x, y
    [x, y, 4, 11, 'sprites/player-left.png', 0, (global_alpha_percentage args)]
  end
  
  def player_md_up args, x, y
    [x, y, 4, 11, 'sprites/player-up.png', 0, (global_alpha_percentage args)]
  end
  
  def player_md_down args, x, y
    [x, y, 4, 11, 'sprites/player-down.png', 0, (global_alpha_percentage args)]
  end
  
  def player_sm args, x, y
    [x, y, 3, 7, 'sprites/player-zoomed-out.png', 0, (global_alpha_percentage args)]
  end
  
  def player_xs args, x, y
    [x, y, 1, 4, 'sprites/player-zoomed-out.png', 0, (global_alpha_percentage args)]
  end

#+end_src

*** Rpg Narrative - Return Of Serenity - require.rb
#+begin_src ruby
  # ./samples/99_genre_rpg_narrative/return_of_serenity/app/require.rb
  require 'app/lowrez_simulator.rb'
  require 'app/storyline_day_one.rb'
  require 'app/storyline_blinking_light.rb'
  require 'app/storyline_serenity_introduction.rb'
  require 'app/storyline_speed_of_light.rb'
  require 'app/storyline_serenity_alive.rb'
  require 'app/storyline_serenity_bio.rb'
  require 'app/storyline_anka.rb'
  require 'app/storyline_final_message.rb'
  require 'app/storyline_final_decision.rb'
  require 'app/storyline.rb'

#+end_src

*** Rpg Narrative - Return Of Serenity - storyline.rb
#+begin_src ruby
  # ./samples/99_genre_rpg_narrative/return_of_serenity/app/storyline.rb
  def hotspot_top
    [4, 61, 56, 3]
  end
  
  def hotspot_bottom
    [4, 0, 56, 3]
  end
  
  def hotspot_top_right
    [62, 35, 3, 25]
  end
  
  def hotspot_bottom_right
    [62, 0, 3, 25]
  end
  
  def storyline_history_include? args, text
    args.state.storyline_history.any? { |s| s.gsub("-", "").gsub(" ", "").include? text.gsub("-", "").gsub(" ", "") }
  end
  
  def blinking_light_side_of_home_render args, lowrez_sprites, lowrez_labels, lowrez_solids
    lowrez_sprites << [48, 44, 5, 5, 'sprites/square.png', 0,  50 * (args.state.tick_count % 50).fdiv(50), 0, 255, 0]
    lowrez_sprites << [49, 45, 3, 3, 'sprites/square.png', 0, 100 * (args.state.tick_count % 50).fdiv(50), 0, 255, 0]
    lowrez_sprites << [50, 46, 1, 1, 'sprites/square.png', 0, 255 * (args.state.tick_count % 50).fdiv(50), 0, 255, 0]
  end
  
  def blinking_light_mountain_pass_render args, lowrez_sprites, lowrez_labels, lowrez_solids
    lowrez_sprites << [18, 47, 5, 5, 'sprites/square.png', 0,  50 * (args.state.tick_count % 50).fdiv(50), 0, 255, 0]
    lowrez_sprites << [19, 48, 3, 3, 'sprites/square.png', 0, 100 * (args.state.tick_count % 50).fdiv(50), 0, 255, 0]
    lowrez_sprites << [20, 49, 1, 1, 'sprites/square.png', 0, 255 * (args.state.tick_count % 50).fdiv(50), 0, 255, 0]
  end
  
  def blinking_light_path_to_observatory_render args, lowrez_sprites, lowrez_labels, lowrez_solids
    lowrez_sprites << [0, 26, 5, 5, 'sprites/square.png', 0,  50 * (args.state.tick_count % 50).fdiv(50), 0, 255, 0]
    lowrez_sprites << [1, 27, 3, 3, 'sprites/square.png', 0, 100 * (args.state.tick_count % 50).fdiv(50), 0, 255, 0]
    lowrez_sprites << [2, 28, 1, 1, 'sprites/square.png', 0, 255 * (args.state.tick_count % 50).fdiv(50), 0, 255, 0]
  end
  
  def blinking_light_observatory_render args, lowrez_sprites, lowrez_labels, lowrez_solids
    lowrez_sprites << [23, 59, 5, 5, 'sprites/square.png', 0,  50 * (args.state.tick_count % 50).fdiv(50), 0, 255, 0]
    lowrez_sprites << [24, 60, 3, 3, 'sprites/square.png', 0, 100 * (args.state.tick_count % 50).fdiv(50), 0, 255, 0]
    lowrez_sprites << [25, 61, 1, 1, 'sprites/square.png', 0, 255 * (args.state.tick_count % 50).fdiv(50), 0, 255, 0]
  end
  
  def blinking_light_inside_observatory_render args, lowrez_sprites, lowrez_labels, lowrez_solids
    lowrez_sprites << [30, 30, 5, 5, 'sprites/square.png', 0,  50 * (args.state.tick_count % 50).fdiv(50), 0, 255, 0]
    lowrez_sprites << [31, 31, 3, 3, 'sprites/square.png', 0, 100 * (args.state.tick_count % 50).fdiv(50), 0, 255, 0]
    lowrez_sprites << [32, 32, 1, 1, 'sprites/square.png', 0, 255 * (args.state.tick_count % 50).fdiv(50), 0, 255, 0]
  end
  
  def decision_graph context_message, context_action, context_result_one, context_result_two, context_result_three = [], context_result_four = []
    result_one_scene, result_one_label, result_one_text = context_result_one
    result_two_scene, result_two_label, result_two_text = context_result_two
    result_three_scene, result_three_label, result_three_text = context_result_three
    result_four_scene, result_four_label, result_four_text = context_result_four
  
    top_level_hash = {
      background: 'sprites/decision.png',
      fade: 60,
      player: [20, 36],
      storylines: [ ],
      scenes: [ ]
    }
  
    confirmation_result_one_hash = {
      background: 'sprites/decision.png',
      scenes: [ ],
      storylines: [ ]
    }
  
    confirmation_result_two_hash = {
      background: 'sprites/decision.png',
      scenes: [ ],
      storylines: [ ]
    }
  
    confirmation_result_three_hash = {
      background: 'sprites/decision.png',
      scenes: [ ],
      storylines: [ ]
    }
  
    confirmation_result_four_hash = {
      background: 'sprites/decision.png',
      scenes: [ ],
      storylines: [ ]
    }
  
    top_level_hash[:storylines] << [ 5, 35, 4, 4, context_message]
    top_level_hash[:storylines] << [20, 35, 4, 4, context_action]
  
    confirmation_result_one_hash[:scenes]       << [20, 35, 4, 4, top_level_hash]
    confirmation_result_one_hash[:scenes]       << [60, 50, 4, 4, result_one_scene]
    confirmation_result_one_hash[:storylines]   << [40, 50, 4, 4, "#{result_one_label}: \"#{result_one_text}\""]
    confirmation_result_one_hash[:scenes]       << [40, 40, 4, 4, confirmation_result_four_hash] if result_four_scene
    confirmation_result_one_hash[:scenes]       << [40, 30, 4, 4, confirmation_result_three_hash] if result_three_scene
    confirmation_result_one_hash[:scenes]       << [40, 20, 4, 4, confirmation_result_two_hash]
  
    confirmation_result_two_hash[:scenes]       << [20, 35, 4, 4, top_level_hash]
    confirmation_result_two_hash[:scenes]       << [40, 50, 4, 4, confirmation_result_one_hash]
    confirmation_result_two_hash[:scenes]       << [40, 40, 4, 4, confirmation_result_four_hash] if result_four_scene
    confirmation_result_two_hash[:scenes]       << [40, 30, 4, 4, confirmation_result_three_hash] if result_three_scene
    confirmation_result_two_hash[:scenes]       << [60, 20, 4, 4, result_two_scene]
    confirmation_result_two_hash[:storylines]   << [40, 20, 4, 4, "#{result_two_label}: \"#{result_two_text}\""]
  
    confirmation_result_three_hash[:scenes]     << [20, 35, 4, 4, top_level_hash]
    confirmation_result_three_hash[:scenes]     << [40, 50, 4, 4, confirmation_result_one_hash]
    confirmation_result_three_hash[:scenes]     << [40, 40, 4, 4, confirmation_result_four_hash]
    confirmation_result_three_hash[:scenes]     << [60, 30, 4, 4, result_three_scene]
    confirmation_result_three_hash[:storylines] << [40, 30, 4, 4, "#{result_three_label}: \"#{result_three_text}\""]
    confirmation_result_three_hash[:scenes]     << [40, 20, 4, 4, confirmation_result_two_hash]
  
    confirmation_result_four_hash[:scenes]      << [20, 35, 4, 4, top_level_hash]
    confirmation_result_four_hash[:scenes]      << [40, 50, 4, 4, confirmation_result_one_hash]
    confirmation_result_four_hash[:scenes]      << [60, 40, 4, 4, result_four_scene]
    confirmation_result_four_hash[:storylines]  << [40, 40, 4, 4, "#{result_four_label}: \"#{result_four_text}\""]
    confirmation_result_four_hash[:scenes]      << [40, 30, 4, 4, confirmation_result_three_hash]
    confirmation_result_four_hash[:scenes]      << [40, 20, 4, 4, confirmation_result_two_hash]
  
    top_level_hash[:scenes]     << [40, 50, 4, 4, confirmation_result_one_hash]
    top_level_hash[:scenes]     << [40, 40, 4, 4, confirmation_result_four_hash] if result_four_scene
    top_level_hash[:scenes]     << [40, 30, 4, 4, confirmation_result_three_hash] if result_three_scene
    top_level_hash[:scenes]     << [40, 20, 4, 4, confirmation_result_two_hash]
  
    top_level_hash
  end
  
  def ship_control_hotspot offset_x, offset_y, a, b, c, d
    results = []
    results << [ 6 + offset_x, 0 + offset_y, 4, 4, a]  if a
    results << [ 1 + offset_x, 5 + offset_y, 4, 4, b]  if b
    results << [ 6 + offset_x, 5 + offset_y, 4, 4, c]  if c
    results << [ 11 + offset_x, 5 + offset_y, 4, 4, d] if d
    results
  end
  
  def reload_current_scene
    if $gtk.args.state.last_hotspot_scene
      set_scene $gtk.args, send($gtk.args.state.last_hotspot_scene, $gtk.args)
      tick $gtk.args
    elsif respond_to? :set_scene
      set_scene $gtk.args, (replied_to_serenity_alive_firmly $gtk.args)
      tick $gtk.args
    end
    $gtk.console.close
  end

#+end_src

*** Rpg Narrative - Return Of Serenity - storyline_anka.rb
#+begin_src ruby
  # ./samples/99_genre_rpg_narrative/return_of_serenity/app/storyline_anka.rb
  def anka_inside_room args
    {
      background: 'sprites/inside-home.png',
      player: [34, 35],
      storylines: [
        [34, 34, 4, 4, "Ahhhh!!! Oh god, it was just- a nightmare."],
      ],
      scenes: [
        [32, -1, 8, 3, :anka_observatory]
      ]
    }
  end
  
  def anka_observatory args
    {
      background: 'sprites/inside-observatory.png',
      fade: 60,
      player: [51, 12],
      storylines: [
        [50, 10, 4, 4,   "Breathe, Hiro. Just see what's there... everything--- will- be okay."]
      ],
      scenes: [
        [30, 18, 5, 12, :anka_inside_mainframe]
      ],
      render_override: :blinking_light_inside_observatory_render
    }
  end
  
  def anka_inside_mainframe args
    {
      player: [32, 4],
      background: 'sprites/mainframe.png',
      fade: 60,
      storylines: [
        [22, 45, 17, 4, (anka_last_reply args)],
        [45, 45,  4, 4, (anka_current_reply args)],
      ],
      scenes: [
        [*hotspot_top_right, :reply_to_anka]
      ]
    }
  end
  
  def reply_to_anka args
    decision_graph anka_current_reply(args),
                   "Matthew's-- wife is doing-- well. What's-- even-- better-- is that he's-- a dad, and he didn't-- even-- know it. Should- I- leave- out the part about-- the crew- being-- in hibernation-- for 20-- years? They- should- enter-- statis-- on a high- note... Right?",
                   [:replied_with_whole_truth, "Whole-- Truth--", anka_reply_whole_truth],
                   [:replied_with_half_truth, "Half-- Truth--", anka_reply_half_truth]
  end
  
  def anka_last_reply args
    if args.state.scene_history.include? :replied_to_serenity_alive_firmly
      return "Buffer--: #{serenity_alive_firm_reply.quote}"
    else
      return "Buffer--: #{serenity_alive_sugarcoated_reply.quote}"
    end
  end
  
  def anka_reply_whole_truth
    "Matthew's wife is doing-- very-- well. In fact, she was pregnant. Matthew-- is a dad. He has a son. But, I need- all-- of-- you-- to brace-- yourselves. You've-- been in statis-- for 20 years. A lot has changed. Most of Earth's-- population--- didn't-- survive. Tell- Matthew-- that I'm-- sorry he didn't-- get to see- his- son grow- up."
  end
  
  def anka_reply_half_truth
    "Matthew's--- wife- is doing-- very-- well. In fact, she was pregnant. Matthew is a dad! It's a boy! Tell- Matthew-- congrats-- for me. Hope-- to see- all of you- soon."
  end
  
  def replied_with_whole_truth args
    {
      background: 'sprites/inside-observatory.png',
      fade: 60,
      player: [32, 21],
      scenes: [[60, 0, 4, 32, :replied_to_anka_back_home]],
      storylines: [
        [30, 18, 5, 12, "Buffer-- has been set to: #{anka_reply_whole_truth.quote}"],
        [30, 10, 5, 4, "I- hope- I- did the right- thing- by laying-- it all- out- there."],
      ]
    }
  end
  
  def replied_with_half_truth args
    {
      background: 'sprites/inside-observatory.png',
      fade: 60,
      player: [32, 21],
      scenes: [[60, 0, 4, 32, :replied_to_anka_back_home]],
      storylines: [
        [30, 18, 5, 12, "Buffer-- has been set to: #{anka_reply_half_truth.quote}"],
        [30, 10, 5, 4, "I- hope- I- did the right- thing- by not giving-- them- the whole- truth."],
      ]
    }
  end
  
  def anka_current_reply args
    if args.state.scene_history.include? :replied_to_serenity_alive_firmly
      return "Hello. This is, Aanka. Sasha-- is still- trying-- to gather-- her wits about-- her, given- the gravity--- of your- last- reply. Thank- you- for being-- honest, and thank- you- for the help- with the ship- diagnostics. I was able-- to retrieve-- all of the navigation--- information---- after-- the battery--- swap. We- are ready-- to head back to Earth. Before-- we go- back- into-- statis, Matthew--- wanted-- to know- how his- wife- is doing. Please- reply-- as soon- as you can. He's-- not going-- to get- into-- the statis-- chamber-- until-- he knows- his wife is okay."
    else
      return "Hello. This is, Aanka. Thank- you for the help- with the ship's-- diagnostics. I was able-- to retrieve-- all of the navigation--- information--- after-- the battery-- swap. I- know-- that- you didn't-- tell- the whole truth- about-- how far we are from- Earth. Don't-- worry. I understand-- why you did it. We- are ready-- to head back to Earth. Before-- we go- back- into-- statis, Matthew--- wanted-- to know- how his- wife- is doing. Please- reply-- as soon- as you can. He's-- not going-- to get- into-- the statis-- chamber-- until-- he knows- his wife is okay."
    end
  end
  
  def replied_to_anka_back_home args
    if args.state.scene_history.include? :replied_with_whole_truth
      return {
        fade: 60,
        background: 'sprites/inside-home.png',
        player: [34, 4],
        storylines: [
          [34, 4, 4, 4, "I- hope-- this pit in my stomach-- is gone-- by tomorrow---."],
        ],
        scenes: [
          [30, 38, 12, 13, :final_message_sad],
        ]
      }
    else
      return {
        fade: 60,
        background: 'sprites/inside-home.png',
        player: [34, 4],
        storylines: [
          [34, 4, 4, 4, "I- get the feeling-- I'm going-- to sleep real well tonight--."],
        ],
        scenes: [
          [30, 38, 12, 13, :final_message_happy],
        ]
      }
    end
  end

#+end_src

*** Rpg Narrative - Return Of Serenity - storyline_blinking_light.rb
#+begin_src ruby
  # ./samples/99_genre_rpg_narrative/return_of_serenity/app/storyline_blinking_light.rb
  def the_blinking_light args
    {
      fade: 60,
      background: 'sprites/side-of-home.png',
      player: [16, 13],
      scenes: [
        [52, 24, 11, 5, :blinking_light_mountain_pass],
      ],
      render_override: :blinking_light_side_of_home_render
    }
  end
  
  def blinking_light_mountain_pass args
    {
      background: 'sprites/mountain-pass-zoomed-out.png',
      player: [4, 4],
      scenes: [
        [18, 47, 5, 5, :blinking_light_path_to_observatory]
      ],
      render_override: :blinking_light_mountain_pass_render
    }
  end
  
  def blinking_light_path_to_observatory args
    {
      background: 'sprites/path-to-observatory.png',
      player: [60, 4],
      scenes: [
        [0, 26, 5, 5, :blinking_light_observatory]
      ],
      render_override: :blinking_light_path_to_observatory_render
    }
  end
  
  def blinking_light_observatory args
    {
      background: 'sprites/observatory.png',
      player: [60, 2],
      scenes: [
        [28, 39, 4, 10, :blinking_light_inside_observatory]
      ],
      render_override: :blinking_light_observatory_render
    }
  end
  
  def blinking_light_inside_observatory args
    {
      background: 'sprites/inside-observatory.png',
      player: [60, 2],
      storylines: [
        [50, 2, 4, 8,   "That's weird. I thought- this- mainframe-- was broken--."]
      ],
      scenes: [
        [30, 18, 5, 12, :blinking_light_inside_mainframe]
      ],
      render_override: :blinking_light_inside_observatory_render
    }
  end
  
  def blinking_light_inside_mainframe args
    {
      background: 'sprites/mainframe.png',
      fade: 60,
      player: [30, 4],
      scenes: [
        [62, 32, 4, 32, :reply_to_introduction]
      ],
      storylines: [
        [43, 43,  8, 8, "\"Mission-- control--, your- main- comm-- channels-- seem-- to be down. My apologies-- for- using-- this low- level-- exploit--. What's-- going-- on down there? We are ready-- for reentry--.\" Message--- Timestamp---: 4- hours-- 23--- minutes-- ago--."],
        [30, 30,  4, 4, "There's-- a low- level-- message-- here... NANI.T.F?"],
        [14, 10, 24, 4, "Oh interesting---. This transistor--- needed-- to be activated--- for the- mainframe-- to work."],
        [14, 20, 24, 4, "What the heck activated--- this thing- though?"]
      ]
    }
  end

#+end_src

*** Rpg Narrative - Return Of Serenity - storyline_day_one.rb
#+begin_src ruby
  # ./samples/99_genre_rpg_narrative/return_of_serenity/app/storyline_day_one.rb
  def day_one_beginning args
    {
      background: 'sprites/side-of-home.png',
      player: [16, 13],
      scenes: [
        [0, 0, 64, 2, :day_one_infront_of_home],
      ],
      storylines: [
        [35, 10, 6, 6,  "Man. Hard to believe- that today- is the 20th--- anniversary-- of The Impact."]
      ]
    }
  end
  
  def day_one_infront_of_home args
    {
      background: 'sprites/front-of-home.png',
      player: [56, 23],
      scenes: [
        [43, 34, 10, 16, :day_one_home],
        [62, 0,  3, 40, :day_one_beginning],
        [0, 4, 3, 20, :day_one_ceremony]
      ],
      storylines: [
        [40, 20, 4, 4, "It looks like everyone- is already- at the rememberance-- ceremony."],
      ]
    }
  end
  
  def day_one_home args
    {
      background: 'sprites/inside-home.png',
      player: [34, 3],
      scenes: [
        [28, 0, 12, 2, :day_one_infront_of_home]
      ],
      storylines: [
        [
          38, 4, 4, 4, "My mansion- in all its glory! Okay yea, it's just a shipping- container-. Apparently-, it's nothing- like the luxuries- of the 2040's. But it's- all we have- in- this day and age. And it'll suffice."
        ],
        [
          28, 7, 4, 7,
          "Ahhh. My reading- couch. It's so comfortable--."
        ],
        [
          38, 21, 4, 4,
          "I'm- lucky- to have a computer--. I'm- one of the few people- with- the skills to put this- thing to good use."
        ],
        [
          45, 37, 4, 8,
          "This corner- of my home- is always- warmer-. It's cause of the ref~lected-- light- from the solar-- panels--, just on the other- side- of this wall. It's hard- to believe- there was o~nce-- an unlimited- amount- of electricity--."
        ],
        [
          32, 40, 8, 10,
          "This isn't- a good time- to sleep. I- should probably- head to the ceremony-."
        ],
        [
          25, 21, 5, 12,
          "Fifteen-- years- of computer-- science-- notes, neatly-- organized. Compiler--- Theory--, Linear--- Algebra---, Game-- Development---... Every-- subject-- imaginable--."
        ]
      ]
    }
  end
  
  def day_one_ceremony args
    {
      background: 'sprites/tribute.png',
      player: [57, 21],
      scenes: [
        [62, 0, 2, 40, :day_one_infront_of_home],
        [0, 24, 2, 40, :day_one_infront_of_library]
      ],
      storylines: [
        [53, 12, 3,  8,  "It's- been twenty- years since The Impact. Twenty- years, since Halley's-- Comet-- set Earth's- blue- sky on fire."],
        [45, 12, 3,  8,  "The space mission- sent to prevent- Earth's- total- destruction--, was a success. Only- 99.9%------ of the world's- population-- died-- that day. Hey, it's- better-- than 100%---- of humanity-- dying."],
        [20, 12, 23, 4, "The monument--- reads:---- Here- stands- the tribute-- to Space- Mission-- Serenity--- and- its- crew. You- have- given-- humanity--- a second-- chance."],
        [15, 12, 3,  8, "Rest- in- peace--- Matthew----, Sasha----, Aanka----"],
      ]
    }
  end
  
  def day_one_infront_of_library args
    {
      background: 'sprites/outside-library.png',
      player: [57, 21],
      scenes: [
        [62, 0, 2, 40, :day_one_ceremony],
        [49, 39, 6, 9, :day_one_library]
      ],
      storylines: [
        [50, 20, 4, 8,  "Shipping- containers-- as far- as the eye- can see. It's- rather- beautiful-- if you ask me. Even- though-- this- view- represents-- all- that's-- left- of humanity-."]
      ]
    }
  end
  
  def day_one_library args
    {
      background: 'sprites/library.png',
      player: [27, 4],
      scenes: [
        [0, 0, 64, 2, :end_day_one_infront_of_library]
      ],
      storylines: [
        [28, 22, 8, 4,  "I grew- up- in this library. I've- read every- book- here. My favorites-- were- of course-- anything- computer-- related."],
        [6, 32, 10, 6, "My favorite-- area--- of the library. The Science-- Section."]
      ]
    }
  end
  
  def end_day_one_infront_of_library args
    {
      background: 'sprites/outside-library.png',
      player: [51, 33],
      scenes: [
        [49, 39, 6, 9, :day_one_library],
        [62, 0, 2, 40, :end_day_one_monument],
      ],
      storylines: [
        [50, 27, 4, 4, "It's getting late. Better get some sleep."]
      ]
    }
  end
  
  def end_day_one_monument args
    {
      background: 'sprites/tribute.png',
      player: [2, 36],
      scenes: [
        [62, 0, 2, 40, :end_day_one_infront_of_home],
      ],
      storylines: [
        [50, 27, 4, 4, "It's getting late. Better get some sleep."],
      ]
    }
  end
  
  def end_day_one_infront_of_home args
    {
      background: 'sprites/front-of-home.png',
      player: [1, 17],
      scenes: [
        [43, 34, 10, 16, :end_day_one_home],
      ],
      storylines: [
        [20, 10, 4, 4, "It's getting late. Better get some sleep."],
      ]
    }
  end
  
  def end_day_one_home args
    {
      background: 'sprites/inside-home.png',
      player: [34, 3],
      scenes: [
        [32, 40, 8, 10, :end_day_one_dream],
      ],
      storylines: [
        [38, 4, 4, 4, "It's getting late. Better get some sleep."],
      ]
    }
  end
  
  def end_day_one_dream args
    {
      background: 'sprites/dream.png',
      fade: 60,
      player: [4, 4],
      scenes: [
        [62, 0, 2, 64, :explaining_the_special_power]
      ],
      storylines: [
        [10, 10, 4, 4, "Why- does this- moment-- always- haunt- my dreams?"],
        [20, 10, 4, 4, "This kid- reads these computer--- science--- books- nonstop-. What's- wrong with him?"],
        [30, 10, 4, 4, "There- is nothing-- wrong- with him. This behavior-- should be encouraged---! In fact-, I think- he's- special---. Have- you seen- him use- a computer---? It's-- almost-- as if he can- speak-- to it."]
      ]
    }
  end
  
  def explaining_the_special_power args
    {
      fade: 60,
      background: 'sprites/inside-home.png',
      player: [32, 30],
      scenes: [
        [
          38, 21, 4, 4, :explaining_the_special_power_inside_computer
        ],
      ]
    }
  end
  
  def explaining_the_special_power_inside_computer args
    {
      background: 'sprites/pc.png',
      fade: 60,
      player: [34, 4],
      scenes: [
        [0, 62, 64, 3, :the_blinking_light]
      ],
      storylines: [
        [14, 20, 24, 4, "So... I have a special-- power--. I don't-- need a mouse-, keyboard--, or even-- a monitor--- to control-- a computer--."],
        [14, 25, 24, 4, "I only-- pretend-- to use peripherals---, so as not- to freak- anyone--- out."],
        [14, 30, 24, 4, "Inside-- this silicon--- Universe---, is the only-- place I- feel- at peace."],
        [14, 35, 24, 4, "It's-- the only-- place where I don't-- feel alone."]
      ]
    }
  end

#+end_src

*** Rpg Narrative - Return Of Serenity - storyline_final_decision.rb
#+begin_src ruby
  # ./samples/99_genre_rpg_narrative/return_of_serenity/app/storyline_final_decision.rb
  def final_decision_side_of_home args
    {
      fade: 120,
      background: 'sprites/side-of-home.png',
      player: [16, 13],
      scenes: [
        [52, 24, 11, 5, :final_decision_mountain_pass],
      ],
      render_override: :blinking_light_side_of_home_render,
      storylines: [
        [28, 13, 8, 4,  "Man. Hard to believe- that today- is the 21st--- anniversary-- of The Impact. Serenity--- will- be- home- soon."]
      ]
    }
  end
  
  def final_decision_mountain_pass args
    {
      background: 'sprites/mountain-pass-zoomed-out.png',
      player: [4, 4],
      scenes: [
        [18, 47, 5, 5, :final_decision_path_to_observatory]
      ],
      render_override: :blinking_light_mountain_pass_render
    }
  end
  
  def final_decision_path_to_observatory args
    {
      background: 'sprites/path-to-observatory.png',
      player: [60, 4],
      scenes: [
        [0, 26, 5, 5, :final_decision_observatory]
      ],
      render_override: :blinking_light_path_to_observatory_render
    }
  end
  
  def final_decision_observatory args
    {
      background: 'sprites/observatory.png',
      player: [60, 2],
      scenes: [
        [28, 39, 4, 10, :final_decision_inside_observatory]
      ],
      render_override: :blinking_light_observatory_render
    }
  end
  
  def final_decision_inside_observatory args
    {
      background: 'sprites/inside-observatory.png',
      player: [60, 2],
      storylines: [],
      scenes: [
        [30, 18, 5, 12, :final_decision_inside_mainframe]
      ],
      render_override: :blinking_light_inside_observatory_render
    }
  end
  
  def final_decision_inside_mainframe args
    {
      player: [32, 4],
      background: 'sprites/mainframe.png',
      storylines: [],
      scenes: [
        [*hotspot_top, :final_decision_ship_status],
      ]
    }
  end
  
  def final_decision_ship_status args
    {
      background: 'sprites/serenity.png',
      fade: 60,
      player: [30, 10],
      scenes: [
        [*hotspot_top_right, :final_decision]
      ],
      storylines: [
        [30,  8, 4, 4, "????"],
        *final_decision_ship_status_shared(args)
      ]
    }
  end
  
  def final_decision args
    decision_graph  "Stasis-- Chambers--: UNDERPOWERED, Life- forms-- will be terminated---- unless-- equilibrium----- is reached.",
                    "I CAN'T DO THIS... But... If-- I-- don't--- bring-- the- chambers--- to- equilibrium-----, they all die...",
                    [:final_decision_game_over_noone, "Kill--- Everyone---", "DO--- NOTHING?"],
                    [:final_decision_game_over_matthew, "Kill--- Sasha---", "KILL--- SASHA?"],
                    [:final_decision_game_over_anka, "Kill--- Aanka---", "KILL--- AANKA?"],
                    [:final_decision_game_over_sasha, "Kill--- Matthew---", "KILL--- MATTHEW?"]
  end
  
  def final_decision_game_over_noone args
    {
      background: 'sprites/tribute-game-over.png',
      player: [53, 14],
      fade: 600
    }
  end
  
  def final_decision_game_over_matthew args
    {
      background: 'sprites/tribute-game-over.png',
      player: [53, 14],
      fade: 600
    }
  end
  
  def final_decision_game_over_anka args
    {
      background: 'sprites/tribute-game-over.png',
      player: [53, 14],
      fade: 600
    }
  end
  
  def final_decision_game_over_sasha args
    {
      background: 'sprites/tribute-game-over.png',
      player: [53, 14],
      fade: 600
    }
  end
  
  def final_decision_ship_status_shared args
    [
      *ship_control_hotspot(24, 22,
                             "Stasis-- Chambers--: UNDERPOWERED, Life- forms-- will be terminated---- unless-- equilibrium----- is reached. WHAT?! NO!",
                             "Matthew's--- Chamber--: UNDER-- THREAT-- OF-- TERMINATION. WHAT?! NO!",
                             "Aanka's--- Chamber--: UNDER-- THREAT-- OF-- TERMINATION.  WHAT?! NO!",
                             "Sasha's--- Chamber--: UNDER-- THREAT-- OF-- TERMINATION. WHAT?! NO!"),
    ]
  end

#+end_src

*** Rpg Narrative - Return Of Serenity - storyline_final_message.rb
#+begin_src ruby
  # ./samples/99_genre_rpg_narrative/return_of_serenity/app/storyline_final_message.rb
  def final_message_sad args
    {
      fade: 60,
      background: 'sprites/inside-home.png',
      player: [34, 35],
      storylines: [
        [34, 34, 4, 4, "Another-- sleepless-- night..."],
      ],
      scenes: [
        [32, -1, 8, 3, :final_message_observatory]
      ]
    }
  end
  
  def final_message_happy args
    {
      fade: 60,
      background: 'sprites/inside-home.png',
      player: [34, 35],
      storylines: [
        [34, 34, 4, 4, "Oh man, I slept like rock!"],
      ],
      scenes: [
        [32, -1, 8, 3, :final_message_observatory]
      ]
    }
  end
  
  def final_message_side_of_home args
    {
      fade: 60,
      background: 'sprites/side-of-home.png',
      player: [16, 13],
      scenes: [
        [52, 24, 11, 5, :final_message_mountain_pass],
      ],
      render_override: :blinking_light_side_of_home_render
    }
  end
  
  def final_message_mountain_pass args
    {
      background: 'sprites/mountain-pass-zoomed-out.png',
      player: [4, 4],
      scenes: [
        [18, 47, 5, 5, :final_message_path_to_observatory],
      ],
      storylines: [
        [18, 13, 5, 5, "Hnnnnnnnggg. My legs-- are still sore- from yesterday."]
      ],
      render_override: :blinking_light_mountain_pass_render
    }
  end
  
  def final_message_path_to_observatory args
    {
      background: 'sprites/path-to-observatory.png',
      player: [60, 4],
      scenes: [
        [0, 26, 5, 5, :final_message_observatory]
      ],
      storylines: [
        [22, 20, 10, 10, "This spot--, on the mountain, right here, it's-- perfect. This- is where- I'll-- yeet-- the person-- who is playing-- this- prank- on me."]
      ],
      render_override: :blinking_light_path_to_observatory_render
    }
  end
  
  def final_message_observatory args
    if args.state.scene_history.include? :replied_with_whole_truth
      return {
        background: 'sprites/inside-observatory.png',
        fade: 60,
        player: [51, 12],
        storylines: [
          [50, 10, 4, 4, "Here-- we- go..."]
        ],
        scenes: [
          [30, 18, 5, 12, :final_message_inside_mainframe]
        ],
        render_override: :blinking_light_inside_observatory_render
      }
    else
      return {
        background: 'sprites/inside-observatory.png',
        fade: 60,
        player: [51, 12],
        storylines: [
          [50, 10, 4, 4, "I feel like I'm-- walking-- on sunshine!"]
        ],
        scenes: [
          [30, 18, 5, 12, :final_message_inside_mainframe]
        ],
        render_override: :blinking_light_inside_observatory_render
      }
    end
  end
  
  def final_message_inside_mainframe args
    {
      player: [32, 4],
      background: 'sprites/mainframe.png',
      fade: 60,
      scenes: [[45, 45,  4, 4, :final_message_check_ship_status]]
    }
  end
  
  def final_message_check_ship_status args
    {
      background: 'sprites/mainframe.png',
      storylines: [
        [45, 45, 4, 4, (final_message_current args)],
      ],
      scenes: [
        [*hotspot_top, :final_message_ship_status],
      ]
    }
  end
  
  def final_message_ship_status args
    {
      background: 'sprites/serenity.png',
      fade: 60,
      player: [30, 10],
      scenes: [
        [30, 50, 4, 4, :final_message_ship_status_reviewed]
      ],
      storylines: [
        [30,  8, 4, 4, "Let me make- sure- everything--- looks good. It'll-- give me peace- of mind."],
        *final_message_ship_status_shared(args)
      ]
    }
  end
  
  def final_message_ship_status_reviewed args
    {
      background: 'sprites/serenity.png',
      fade: 60,
      scenes: [
        [*hotspot_bottom, :final_message_summary]
      ],
      storylines: [
        [0, 62, 62, 3, "Whew. Everyone-- is in their- chambers. The engines-- are roaring-- and Serenity-- is coming-- home."],
      ]
    }
  end
  
  def final_message_ship_status_shared args
    [
      *ship_control_hotspot( 0, 50,
                             "Stasis-- Chambers--: Online, All chambers-- are powered. Battery--- Allocation---: 3--- of-- 3--.",
                             "Matthew's--- Chamber--: OCCUPIED----",
                             "Aanka's--- Chamber--: OCCUPIED----",
                             "Sasha's--- Chamber--: OCCUPIED----"),
      *ship_control_hotspot(12, 35,
                            "Life- Support--: Not-- Needed---",
                            "O2--- Production---: OFF---",
                            "CO2--- Scrubbers---: OFF---",
                            "H2O--- Production---: OFF---"),
      *ship_control_hotspot(24, 20,
                            "Navigation: Offline---",
                            "Sensor: OFF---",
                            "Heads- Up- Display: DAMAGED---",
                            "Arithmetic--- Unit: DAMAGED----"),
      *ship_control_hotspot(36, 35,
                            "COMM: Underpowered----",
                            "Text: ON---",
                            "Audio: SEGFAULT---",
                            "Video: DAMAGED---"),
      *ship_control_hotspot(48, 50,
                            "Engine: Online, Coordinates--- Set- for Earth. Battery--- Allocation---: 3--- of-- 3---",
                            "Engine I: ON---",
                            "Engine II: ON---",
                            "Engine III: ON---")
    ]
  end
  
  def final_message_last_reply args
    if args.state.scene_history.include? :replied_with_whole_truth
      return "Buffer--: #{anka_reply_whole_truth.quote}"
    else
      return "Buffer--: #{anka_reply_half_truth.quote}"
    end
  end
  
  def final_message_current args
    if args.state.scene_history.include? :replied_with_whole_truth
      return "Hey... It's-- me Sasha. Aanka-- is trying-- her best to comfort-- Matthew. This- is the first- time- I've-- ever-- seen-- Matthew-- cry. We'll-- probably-- be in stasis-- by the time you get this message--. Thank- you- again-- for all your help. I look forward-- to meeting-- you in person."
    else
      return "Hey! It's-- me Sasha! LOL! Aanka-- and Matthew-- are dancing-- around-- like- goofballs--! They- are both- so adorable! Only-- this- tiny-- little-- genius-- can make-- a battle-- hardened-- general--- put- on a tiara-- and dance- around-- like a fairy-- princess-- XD------ Anyways, we are heading-- back into-- the chambers--. I hope our welcome-- home- parade-- has fireworks!"
    end
  end
  
  def final_message_summary args
    if args.state.scene_history.include? :replied_with_whole_truth
      return {
        background: 'sprites/inside-observatory.png',
        fade: 60,
        player: [31, 11],
        scenes: [[60, 0, 4, 32, :final_decision_side_of_home]],
        storylines: [
          [30, 10, 5, 4, "I can't-- imagine-- what they are feeling-- right now. But at least- they- know everything---, and we can- concentrate-- on rebuilding--- this world-- right- off the bat. I can't-- wait to see the future-- they'll-- help- build."],
        ]
      }
    else
      return {
        background: 'sprites/inside-observatory.png',
        fade: 60,
        player: [31, 11],
        scenes: [[60, 0, 4, 32, :final_decision_side_of_home]],
        storylines: [
          [30, 10, 5, 4, "They all sounded-- so happy. I know- they'll-- be in for a tough- dose- of reality--- when they- arrive. But- at least- they'll-- be around-- all- of us. We'll-- help them- cope."],
        ]
      }
    end
  end

#+end_src

*** Rpg Narrative - Return Of Serenity - storyline_serenity_alive.rb
#+begin_src ruby
  # ./samples/99_genre_rpg_narrative/return_of_serenity/app/storyline_serenity_alive.rb
  def serenity_alive_side_of_home args
    {
      fade: 60,
      background: 'sprites/side-of-home.png',
      player: [16, 13],
      scenes: [
        [52, 24, 11, 5, :serenity_alive_mountain_pass],
      ],
      render_override: :blinking_light_side_of_home_render
    }
  end
  
  def serenity_alive_mountain_pass args
    {
      background: 'sprites/mountain-pass-zoomed-out.png',
      player: [4, 4],
      scenes: [
        [18, 47, 5, 5, :serenity_alive_path_to_observatory],
      ],
      storylines: [
        [18, 13, 5, 5, "Hnnnnnnnggg. My legs-- are still sore- from yesterday."]
      ],
      render_override: :blinking_light_mountain_pass_render
    }
  end
  
  def serenity_alive_path_to_observatory args
    {
      background: 'sprites/path-to-observatory.png',
      player: [60, 4],
      scenes: [
        [0, 26, 5, 5, :serenity_alive_observatory]
      ],
      storylines: [
        [22, 20, 10, 10, "This spot--, on the mountain, right here, it's-- perfect. This- is where- I'll-- yeet-- the person-- who is playing-- this- prank- on me."]
      ],
      render_override: :blinking_light_path_to_observatory_render
    }
  end
  
  def serenity_alive_observatory args
    {
      background: 'sprites/observatory.png',
      player: [60, 2],
      scenes: [
        [28, 39, 4, 10, :serenity_alive_inside_observatory]
      ],
      render_override: :blinking_light_observatory_render
    }
  end
  
  def serenity_alive_inside_observatory args
    {
      background: 'sprites/inside-observatory.png',
      player: [60, 2],
      storylines: [],
      scenes: [
        [30, 18, 5, 12, :serenity_alive_inside_mainframe]
      ],
      render_override: :blinking_light_inside_observatory_render
    }
  end
  
  def serenity_alive_inside_mainframe args
    {
      background: 'sprites/mainframe.png',
      fade: 60,
      player: [30, 4],
      scenes: [
        [*hotspot_top, :serenity_alive_ship_status],
      ],
      storylines: [
        [22, 45, 17, 4, (serenity_alive_last_reply args)],
        [45, 45,  4, 4, (serenity_alive_current_message args)],
      ]
    }
  end
  
  def serenity_alive_ship_status args
    {
      background: 'sprites/serenity.png',
      fade: 60,
      player: [30, 10],
      scenes: [
        [30, 50, 4, 4, :serenity_alive_ship_status_reviewed]
      ],
      storylines: [
        [30,  8, 4, 4, "Serenity? THE--- Mission-- Serenity?! How is that possible? They- are supposed-- to be dead."],
        [30, 10, 4, 4, "I... can't-- believe-- it. I- can access-- Serenity's-- computer? I- guess my \"superpower----\" isn't limited-- by proximity-- to- a machine--."],
        *serenity_alive_shared_ship_status(args)
      ]
    }
  end
  
  def serenity_alive_ship_status_reviewed args
    {
      background: 'sprites/serenity.png',
      fade: 60,
      scenes: [
        [*hotspot_bottom, :serenity_alive_time_to_reply]
      ],
      storylines: [
        [0, 62, 62, 3, "Okay. Reviewing-- everything--, it looks- like- I- can- take- the batteries--- from the Stasis--- Chambers--- and- Engine--- to keep- the crew-- alive-- and-- their-- location--- pinpointed---."],
      ]
    }
  end
  
  def serenity_alive_time_to_reply args
    decision_graph serenity_alive_current_message(args),
                    "Okay... time to deliver the bad news...",
                    [:replied_to_serenity_alive_firmly, "Firm-- Reply", serenity_alive_firm_reply],
                    [:replied_to_serenity_alive_kindly, "Sugar-- Coated---- Reply", serenity_alive_sugarcoated_reply]
  end
  
  def serenity_alive_shared_ship_status args
    [
      *ship_control_hotspot( 0, 50,
                             "Stasis-- Chambers--: Online, All chambers-- are powered. Battery--- Allocation---: 3--- of-- 3--, Hmmm. They don't-- need this to be powered-- right- now. Everyone-- is awake.",
                             nil,
                             nil,
                             nil),
      *ship_control_hotspot(12, 35,
                            "Life- Support--: Offline, Unable--- to- Sustain-- Life. Battery--- Allocation---: 0--- of-- 3---, Okay. That is definitely---- not a good thing.",
                            nil,
                            nil,
                            nil),
      *ship_control_hotspot(24, 20,
                            "Navigation: Offline, Unable--- to- Calculate--- Location. Battery--- Allocation---: 0--- of-- 3---, Whelp. No wonder-- Sasha-- can't-- get- any-- readings. Their- Navigation--- is completely--- offline.",
                            nil,
                            nil,
                            nil),
      *ship_control_hotspot(36, 35,
                            "COMM: Underpowered----, Limited--- to- Text-- Based-- COMM. Battery--- Allocation---: 1--- of-- 3---, It's-- lucky- that- their- COMM---- system was able to survive-- twenty-- years--. Just- barely-- it seems.",
                            nil,
                            nil,
                            nil),
      *ship_control_hotspot(48, 50,
                            "Engine: Online, Full- Control-- Available. Battery--- Allocation---: 3--- of-- 3---, Hmmm. No point of having an engine-- online--, if you don't- know- where you're-- going.",
                            nil,
                            nil,
                            nil)
    ]
  end
  
  def serenity_alive_firm_reply
    "Serenity, you are at a distance-- farther-- than- Neptune. All- of the ship's-- systems-- are failing. Please- move the batteries---- from- the Stasis-- Chambers-- over- to- Life-- Support--. I also-- need- you to move-- the batteries---- from- the Engines--- to your Navigation---- System."
  end
  
  def serenity_alive_sugarcoated_reply
    "So... you- are- a teeny--- tiny--- bit--- farther-- from Earth- than you think. And you have a teeny--- tiny--- problem-- with your ship. Please-- move the batteries--- from the Stasis--- Chambers--- over to Life--- Support---. I also need you to move the batteries--- from the Engines--- to your- Navigation--- System. Don't-- worry-- Sasha. I'll-- get y'all-- home."
  end
  
  def replied_to_serenity_alive_firmly args
    {
      background: 'sprites/inside-observatory.png',
      fade: 60,
      player: [32, 21],
      scenes: [
        [*hotspot_bottom_right, :serenity_alive_path_from_observatory]
      ],
      storylines: [
        [30, 18, 5, 12, "Buffer-- has been set to: #{serenity_alive_firm_reply.quote}"],
        *serenity_alive_reply_completed_shared_hotspots(args),
      ]
    }
  end
  
  def replied_to_serenity_alive_kindly args
    {
      background: 'sprites/inside-observatory.png',
      fade: 60,
      player: [32, 21],
      scenes: [
        [*hotspot_bottom_right, :serenity_alive_path_from_observatory]
      ],
      storylines: [
        [30, 18, 5, 12, "Buffer-- has been set to: #{serenity_alive_sugarcoated_reply.quote}"],
        *serenity_alive_reply_completed_shared_hotspots(args),
      ]
    }
  end
  
  def serenity_alive_path_from_observatory args
    {
      fade: 60,
      background: 'sprites/path-to-observatory.png',
      player: [4, 21],
      scenes: [
        [*hotspot_bottom_right, :serenity_bio_infront_of_home]
      ],
      storylines: [
        [22, 20, 10, 10, "I'm not sure what's-- worse. Waiting-- for Sasha's-- reply. Or jumping-- off- from- right- here."]
      ]
    }
  end
  
  def serenity_alive_reply_completed_shared_hotspots args
    [
      [30, 10, 5, 4, "I guess it wasn't-- a joke- after-- all."],
      [40, 10, 5, 4, "I barely-- remember--- the- history----- of the crew."],
      [50, 10, 5, 4, "It probably--- wouldn't-- hurt- to- refresh-- my memory--."]
    ]
  end
  
  def serenity_alive_last_reply args
    if args.state.scene_history.include? :replied_to_introduction_seriously
      return "Buffer--: \"Hello, Who- is sending-- this message--?\""
    else
      return "Buffer--: \"New- phone. Who dis?\""
    end
  end
  
  def serenity_alive_current_message args
    if args.state.scene_history.include? :replied_to_introduction_seriously
      "This- is Sasha. The Serenity--- crew-- is out of hibernation---- and ready-- for Earth reentry--. But, it seems like we are having-- trouble-- with our Navigation---- systems. Please advise.".quote
    else
      "LOL! Thanks for the laugh. I needed that. This- is Sasha. The Serenity--- crew-- is out of hibernation---- and ready-- for Earth reentry--. But, it seems like we are having-- trouble-- with our Navigation---- systems. Can you help me out- babe?".quote
    end
  end

#+end_src

*** Rpg Narrative - Return Of Serenity - storyline_serenity_bio.rb
#+begin_src ruby
  # ./samples/99_genre_rpg_narrative/return_of_serenity/app/storyline_serenity_bio.rb
  def serenity_bio_infront_of_home args
    {
      fade: 60,
      background: 'sprites/front-of-home.png',
      player: [54, 23],
      scenes: [
        [44, 34, 8, 14, :serenity_bio_inside_home],
        [0, 3, 3, 22, :serenity_bio_library]
      ]
    }
  end
  
  def serenity_bio_inside_home args
    {
      background: 'sprites/inside-home.png',
      player: [34, 4],
      storylines: [
        [34, 4, 4, 4, "I'm--- completely--- exhausted."],
      ],
      scenes: [
        [30, 38, 12, 13, :serenity_bio_restless_sleep],
        [32, 0, 8, 3, :serenity_bio_infront_of_home],
      ]
    }
  end
  
  def serenity_bio_restless_sleep args
    {
      fade: 60,
      background: 'sprites/inside-home.png',
      storylines: [
        [32, 38, 10, 13, "I can't-- seem to sleep. I know nothing-- about the- crew-. Maybe- I- should- go read- up- on- them."],
      ],
      scenes: [
        [32, 0, 8, 3, :serenity_bio_infront_of_home],
      ]
    }
  end
  
  def serenity_bio_library args
    {
      background: 'sprites/library.png',
      fade: 60,
      player: [30, 7],
      scenes: [
        [21, 35, 3, 18, :serenity_bio_book]
      ]
    }
  end
  
  def serenity_bio_book args
    {
      background: 'sprites/book.png',
      fade: 60,
      player: [6, 52],
      storylines: [
        [ 4, 50, 56, 4, "The Title-- Reads: Never-- Forget-- Mission-- Serenity---"],
  
        [ 4, 38,  8, 8, "Name: Matthew--- R. Sex: Male--- Age-- at-- Departure: 36-----"],
        [14, 38, 46, 8, "Tribute-- Text: Matthew graduated-- Magna-- Cum-- Laude-- from MIT--- with-- a- PHD---- in Aero-- Nautical--- Engineering. He was immensely--- competitive, and had an insatiable---- thirst- for aerial-- battle. From the age of twenty, he remained-- undefeated--- in the Israeli-- Air- Force- \"Blue Flag\" combat-- exercises. By the age of 29--- he had already-- risen through- the ranks, and became-- the Lieutenant--- General--- of Lufwaffe. Matthew-- volenteered-- to- pilot-- Mission-- Serenity. To- this day, his wife- and son- are pillars-- of strength- for us. Rest- in Peace- Matthew, we are sorry-- that- news of the pregancy-- never-- reached- you. Please forgive us."],
  
        [4,  26,  8, 8, "Name: Aanka--- P. Sex: Female--- Age-- at-- Departure: 9-----"],
        [14, 26, 46, 8, "Tribute-- Text: Aanka--- gratuated--- Magna-- Cum- Laude-- from MIT, at- the- age- of eight, with a- PHD---- in Astro-- Physics. Her-- IQ--- was over 390, the highest-- ever- recorded--- IQ-- in- human-- history. She changed- the landscape-- of Physics-- with her efforts- in- unravelling--- the mysteries--- of- Dark- Matter--. Anka discovered-- the threat- of Halley's-- Comet-- collision--- with Earth. She spear headed-- the global-- effort-- for Misson-- Serenity. Her- multilingual--- address-- to- the world-- brought- us all hope."],
  
        [4,  14,  8, 8, "Name: Sasha--- N. Sex: Female--- Age-- at-- Departure: 29-----"],
        [14, 14, 46, 8, "Tribute-- Text: Sasha gratuated-- Magna-- Cum- Laude-- from MIT--- with-- a- PHD---- in Computer---- Science----. She-- was-- brilliant--, strong- willed--, and-- a-- stunningly--- beautiful--- woman---. Sasha---- is- the- creator--- of the world's--- first- Ruby--- Quantum-- Machine---. After-- much- critical--- acclaim--, the Quantum-- Computer-- was placed in MIT's---- Museam-- next- to- Richard--- G. and Thomas--- K.'s---- Lisp-- Machine---. Her- engineering--- skills-- were-- paramount--- for Mission--- Serenity's--- success. Humanity-- misses-- you-- dearly,-- Sasha--. Life-- shines-- a dimmer-- light-- now- that- your- angelic- voice-- can never- be heard- again."],
      ],
      scenes: [
        [*hotspot_bottom, :serenity_bio_finally_to_bed]
      ]
    }
  end
  
  def serenity_bio_finally_to_bed args
    {
      fade: 60,
      background: 'sprites/inside-home.png',
      player: [35, 3],
      storylines: [
        [34, 4, 4, 4, "Maybe-- I'll-- be able-- to sleep- now..."],
      ],
      scenes: [
        [32, 38, 10, 13, :bad_dream],
      ]
    }
  end
  
  def bad_dream args
    {
      fade: 120,
      background: 'sprites/inside-home.png',
      player: [34, 35],
      storylines: [
        [34, 34, 4, 4, "Man. I did not- sleep- well- at all..."],
      ],
      scenes: [
        [32, -1, 8, 3, :bad_dream_observatory]
      ]
    }
  end
  
  def bad_dream_observatory args
    {
      background: 'sprites/inside-observatory.png',
      fade: 120,
      player: [51, 12],
      storylines: [
        [50, 10, 4, 4,   "Breathe, Hiro. Just see what's there... everything--- will- be okay."]
      ],
      scenes: [
        [30, 18, 5, 12, :bad_dream_inside_mainframe]
      ],
      render_override: :blinking_light_inside_observatory_render
    }
  end
  
  def bad_dream_inside_mainframe args
    {
      player: [32, 4],
      background: 'sprites/mainframe.png',
      fade: 120,
      storylines: [
        [22, 45, 17, 4, (bad_dream_last_reply args)],
      ],
      scenes: [
        [45, 45,  4, 4, :bad_dream_everyone_dead],
      ]
    }
  end
  
  def bad_dream_everyone_dead args
    {
      background: 'sprites/mainframe.png',
      storylines: [
        [22, 45, 17, 4, (bad_dream_last_reply args)],
        [45, 45,  4, 4, "Hi-- Hiro. This is Sasha. By the time- you get this- message, chances-- are we will- already-- be- dead. The batteries--- got- damaged-- during-- removal. And- we don't-- have enough-- power-- for Life-- Support. The air-- is- already--- starting-- to taste- bad. It... would- have been- nice... to go- on a date--- with- you-- when-- I- got- back- to Earth. Anyways, good-- bye-- Hiro-- XOXOXO----"],
        [22,  5, 17, 4, "Meh. Whatever, I didn't-- want to save them anyways. What- a pain- in my ass."],
      ],
      scenes: [
        [*hotspot_bottom, :anka_inside_room]
      ]
    }
  end
  
  def bad_dream_last_reply args
    if args.state.scene_history.include? :replied_to_serenity_alive_firmly
      return "Buffer--: #{serenity_alive_firm_reply.quote}"
    else
      return "Buffer--: #{serenity_alive_sugarcoated_reply.quote}"
    end
  end

#+end_src

*** Rpg Narrative - Return Of Serenity - storyline_serenity_introduction.rb
#+begin_src ruby
  # ./samples/99_genre_rpg_narrative/return_of_serenity/app/storyline_serenity_introduction.rb
  # decision_graph "Message from Sasha",
  #                "I should reply.",
  #                [:replied_to_introduction_seriously,  "Reply Seriously", "Who is this?"],
  # [:replied_to_introduction_humorously, "Reply Humorously", "New phone who dis?"]
  def reply_to_introduction args
    decision_graph  "\"Mission-- control--, your- main- comm-- channels-- seem-- to be down. My apologies-- for- using-- this low- level-- exploit--. What's-- going-- on down there? We are ready-- for reentry--.\" Message--- Timestamp---: 4- hours-- 23--- minutes-- ago--.",
                    "Whoever-- pulled- off this exploit-- knows their stuff. I should reply--.",
                    [:replied_to_introduction_seriously,  "Serious Reply",  "Hello, Who- is sending-- this message--?"],
                    [:replied_to_introduction_humorously, "Humorous Reply", "New phone, who dis?"]
  end
  
  def replied_to_introduction_seriously args
    {
      background: 'sprites/inside-observatory.png',
      fade: 60,
      player: [32, 21],
      scenes: [
        *replied_to_introduction_shared_scenes(args)
      ],
      storylines: [
        [30, 18, 5, 12, "Buffer-- has been set to: \"Hello, Who- is sending-- this message--?\""],
        *replied_to_introduction_shared_storylines(args)
      ]
    }
  end
  
  def replied_to_introduction_humorously args
    {
      background: 'sprites/inside-observatory.png',
      fade: 60,
      player: [32, 21],
      scenes: [
        *replied_to_introduction_shared_scenes(args)
      ],
      storylines: [
        [30, 18, 5, 12, "Buffer-- has been set to: \"New- phone. Who dis?\""],
        *replied_to_introduction_shared_storylines(args)
      ]
    }
  end
  
  def replied_to_introduction_shared_storylines args
    [
      [30, 10, 5, 4, "It's-- going-- to take a while-- for this reply-- to make it's-- way back."],
      [40, 10, 5, 4, "4- hours-- to send a message-- at light speed?! How far away-- is the sender--?"],
      [50, 10, 5, 4, "I know- I've-- read about-- light- speed- travel-- before--. Maybe-- the library--- still has that- poster."]
    ]
  end
  
  def replied_to_introduction_shared_scenes args
    [[60, 0, 4, 32, :replied_to_introduction_observatory]]
  end
  
  def replied_to_introduction_observatory args
    {
      background: 'sprites/observatory.png',
      player: [28, 39],
      scenes: [
        [60, 0, 4, 32, :replied_to_introduction_path_to_observatory]
      ]
    }
  end
  
  def replied_to_introduction_path_to_observatory args
    {
      background: 'sprites/path-to-observatory.png',
      player: [0, 26],
      scenes: [
        [60, 0, 4, 20, :replied_to_introduction_mountain_pass]
      ],
    }
  end
  
  def replied_to_introduction_mountain_pass args
    {
      background: 'sprites/mountain-pass-zoomed-out.png',
      player: [21, 48],
      scenes: [
        [0, 0, 15, 4, :replied_to_introduction_side_of_home]
      ],
      storylines: [
        [15, 28, 5, 3, "At least I'm-- getting-- my- exercise-- in- for- today--."]
      ]
    }
  end
  
  def replied_to_introduction_side_of_home args
    {
      background: 'sprites/side-of-home.png',
      player: [58, 29],
      scenes: [
        [2, 0, 61, 2, :speed_of_light_front_of_home]
      ],
    }
  end

#+end_src

*** Rpg Narrative - Return Of Serenity - storyline_speed_of_light.rb
#+begin_src ruby
  # ./samples/99_genre_rpg_narrative/return_of_serenity/app/storyline_speed_of_light.rb
  def speed_of_light_front_of_home args
    {
      background: 'sprites/front-of-home.png',
      player: [54, 23],
      scenes: [
        [44, 34, 8, 14, :speed_of_light_inside_home],
        [0, 3, 3, 22, :speed_of_light_outside_library]
      ]
    }
  end
  
  def speed_of_light_inside_home args
    {
      background: 'sprites/inside-home.png',
      player: [35, 4],
      storylines: [
        [30, 38, 12, 13, "Can't- sleep right now. I have to- find- out- why- it took- over-- 4- hours-- to receive-- that message."]
      ],
      scenes: [
        [32, 0, 8, 3, :speed_of_light_front_of_home],
      ]
    }
  end
  
  def speed_of_light_outside_library args
    {
      background: 'sprites/outside-library.png',
      player: [55, 19],
      scenes: [
        [49, 39, 6, 10, :speed_of_light_library],
        [61, 11, 3, 20, :speed_of_light_front_of_home]
      ]
    }
  end
  
  def speed_of_light_library args
    {
      background: 'sprites/library.png',
      player: [30, 7],
      scenes: [
        [3, 50, 10, 3, :speed_of_light_celestial_bodies_diagram]
      ]
    }
  end
  
  def speed_of_light_celestial_bodies_diagram args
    {
      background: 'sprites/planets.png',
      fade: 60,
      player: [30, 3],
      scenes: [
        [56 - 2, 10, 5, 5, :speed_of_light_distance_discovered]
      ],
      storylines: [
        [30, 2, 4, 4, "Here- it is! This is a diagram--- of the solar-- system--. It was printed-- over-- fifty-- years- ago. Geez-- that's-- old."],
  
        [ 0 - 2, 10, 5, 5, "The label- reads: Sun. The length- of the Astronomical-------- Unit-- (AU), is the distance-- from the Sun- to the Earth. Which is about 150--- million--- kilometers----."],
        [ 7 - 2, 10, 5, 5, "The label- reads: Mercury. Distance from Sun: 0.39AU------------ or- 3----- light-- minutes--."],
        [14 - 2, 10, 5, 5, "The label- reads: Venus. Distance from Sun: 0.72AU------------ or- 6----- light-- minutes--."],
        [21 - 2, 10, 5, 5, "The label- reads: Earth. Distance from Sun: 1.00AU------------ or- 8----- light-- minutes--."],
        [28 - 2, 10, 5, 5, "The label- reads: Mars. Distance from Sun: 1.52AU------------ or- 12----- light-- minutes--."],
        [35 - 2, 10, 5, 5, "The label- reads: Jupiter. Distance from Sun: 5.20AU------------ or- 45----- light-- minutes--."],
        [42 - 2, 10, 5, 5, "The label- reads: Saturn. Distance from Sun: 9.53AU------------ or- 79----- light-- minutes--."],
        [49 - 2, 10, 5, 5, "The label- reads: Uranus. Distance from Sun: 19.81AU------------ or- 159----- light-- minutes--."],
        # [56 - 2, 15, 4, 4, "The label- reads: Neptune. Distance from Sun: 30.05AU------------ or- 4.1----- light-- hours--."],
        [63 - 2, 10, 5, 5, "The label- reads: Pluto. Wait. WTF? Pluto-- isn't-- a planet."],
      ]
    }
  end
  
  def speed_of_light_distance_discovered args
    {
      background: 'sprites/planets.png',
      scenes: [
        [13, 0, 44, 3, :speed_of_light_end_of_day]
      ],
      storylines: [
        [ 0 - 2, 10, 5, 5, "The label- reads: Sun. The length- of the Astronomical-------- Unit-- (AU), is the distance-- from the Sun- to the Earth. Which is about 150--- million--- kilometers----."],
        [ 7 - 2, 10, 5, 5, "The label- reads: Mercury. Distance from Sun: 0.39AU------------ or- 3----- light-- minutes--."],
        [14 - 2, 10, 5, 5, "The label- reads: Venus. Distance from Sun: 0.72AU------------ or- 6----- light-- minutes--."],
        [21 - 2, 10, 5, 5, "The label- reads: Earth. Distance from Sun: 1.00AU------------ or- 8----- light-- minutes--."],
        [28 - 2, 10, 5, 5, "The label- reads: Mars. Distance from Sun: 1.52AU------------ or- 12----- light-- minutes--."],
        [35 - 2, 10, 5, 5, "The label- reads: Jupiter. Distance from Sun: 5.20AU------------ or- 45----- light-- minutes--."],
        [42 - 2, 10, 5, 5, "The label- reads: Saturn. Distance from Sun: 9.53AU------------ or- 79----- light-- minutes--."],
        [49 - 2, 10, 5, 5, "The label- reads: Uranus. Distance from Sun: 19.81AU------------ or- 159----- light-- minutes--."],
        [56 - 2, 10, 5, 5, "The label- reads: Neptune. Distance from Sun: 30.05AU------------ or- 4.1----- light-- hours--. What?! The message--- I received-- was from a source-- farther-- than-- Neptune?!"],
        [63 - 2, 10, 5, 5, "The label- reads: Pluto. Dista- Wait... Pluto-- isn't-- a planet. People-- thought- Pluto-- was a planet-- back- then?--"],
      ]
    }
  end
  
  def speed_of_light_end_of_day args
    {
      fade: 60,
      background: 'sprites/inside-home.png',
      player: [35, 0],
      storylines: [
        [35, 10, 4, 4, "Wonder-- what the reply-- will be. Who- the hell is contacting--- me from beyond-- Neptune? This- has to be some- kind- of- joke."]
      ],
      scenes: [
        [31, 38, 10, 12, :serenity_alive_side_of_home]
      ]
    }
  end

#+end_src

*** Rpg Roguelike - Roguelike Starting Point - constants.rb
#+begin_src ruby
  # ./samples/99_genre_rpg_roguelike/01_roguelike_starting_point/app/constants.rb
  SHOW_LEGEND = true
  SOURCE_TILE_SIZE = 16
  DESTINATION_TILE_SIZE = 16
  TILE_SHEET_SIZE = 256
  TILE_R = 0
  TILE_G = 0
  TILE_B = 0
  TILE_A = 255

#+end_src

*** Rpg Roguelike - Roguelike Starting Point - legend.rb
#+begin_src ruby
  # ./samples/99_genre_rpg_roguelike/01_roguelike_starting_point/app/legend.rb
  def tick_legend args
    return unless SHOW_LEGEND
  
    legend_padding = 16
    legend_x = 1280 - TILE_SHEET_SIZE - legend_padding
    legend_y =  720 - TILE_SHEET_SIZE - legend_padding
    tile_sheet_sprite = [legend_x,
                         legend_y,
                         TILE_SHEET_SIZE,
                         TILE_SHEET_SIZE,
                         'sprites/simple-mood-16x16.png', 0,
                         TILE_A,
                         TILE_R,
                         TILE_G,
                         TILE_B]
  
    if args.inputs.mouse.point.inside_rect? tile_sheet_sprite
      mouse_row = args.inputs.mouse.point.y.idiv(SOURCE_TILE_SIZE)
      tile_row = 15 - (mouse_row - legend_y.idiv(SOURCE_TILE_SIZE))
  
      mouse_col = args.inputs.mouse.point.x.idiv(SOURCE_TILE_SIZE)
      tile_col = (mouse_col - legend_x.idiv(SOURCE_TILE_SIZE))
  
      args.outputs.primitives << [legend_x - legend_padding * 2,
                                  mouse_row * SOURCE_TILE_SIZE, 256 + legend_padding * 2, 16, 128, 128, 128, 64].solid
  
      args.outputs.primitives << [mouse_col * SOURCE_TILE_SIZE,
                                  legend_y - legend_padding * 2, 16, 256 + legend_padding * 2, 128, 128, 128, 64].solid
  
      sprite_key = sprite_lookup.find { |k, v| v == [tile_row, tile_col] }
      if sprite_key
        member_name, _ = sprite_key
        member_name = member_name_as_code member_name
        args.outputs.labels << [660, 70, "# CODE SAMPLE (place in the tick_game method located in main.rb)", -1, 0]
        args.outputs.labels << [660, 50, "#                                    GRID_X, GRID_Y, TILE_KEY", -1, 0]
        args.outputs.labels << [660, 30, "args.outputs.sprites << tile_in_game(     5,      6, #{member_name}    )", -1, 0]
      else
        args.outputs.labels << [660, 50, "Tile [#{tile_row}, #{tile_col}] not found. Add a key and value to app/sprite_lookup.rb:", -1, 0]
        args.outputs.labels << [660, 30, "{ \"some_string\" => [#{tile_row}, #{tile_col}] } OR { some_symbol: [#{tile_row}, #{tile_col}] }.", -1, 0]
      end
  
    end
  
    # render the sprite in the top right with a padding to the top and right so it's
    # not flush against the edge
    args.outputs.sprites << tile_sheet_sprite
  
    # carefully place some ascii arrows to show the legend labels
    args.outputs.labels  <<  [895, 707, "ROW --->"]
    args.outputs.labels  <<  [943, 412, "       ^"]
    args.outputs.labels  <<  [943, 412, "       |"]
    args.outputs.labels  <<  [943, 394, "COL ---+"]
  
    # use the tile sheet to print out row and column numbers
    args.outputs.sprites << 16.map_with_index do |i|
      sprite_key = i % 10
      [
        tile(1280 - TILE_SHEET_SIZE - legend_padding * 2 - SOURCE_TILE_SIZE,
              720 - legend_padding * 2 - (SOURCE_TILE_SIZE * i),
              sprite(sprite_key)),
        tile(1280 - TILE_SHEET_SIZE - SOURCE_TILE_SIZE + (SOURCE_TILE_SIZE * i),
              720 - TILE_SHEET_SIZE - legend_padding * 3, sprite(sprite_key))
      ]
    end
  end

#+end_src

*** Rpg Roguelike - Roguelike Starting Point - main.rb
#+begin_src ruby
  # ./samples/99_genre_rpg_roguelike/01_roguelike_starting_point/app/main.rb
  require 'app/constants.rb'
  require 'app/sprite_lookup.rb'
  require 'app/legend.rb'
  
  def tick args
    tick_game args
    tick_legend args
  end
  
  def tick_game args
    # setup the grid
    args.state.grid.padding = 104
    args.state.grid.size = 512
  
    # set up your game
    # initialize the game/game defaults. ||= means that you only initialize it if
    # the value isn't alread initialized
    args.state.player.x ||= 0
    args.state.player.y ||= 0
  
    args.state.enemies ||= [
      { x: 10, y: 10, type: :goblin, tile_key: :G },
      { x: 15, y: 30, type: :rat,    tile_key: :R }
    ]
  
    args.state.info_message ||= "Use arrow keys to move around."
  
    # handle keyboard input
    # keyboard input (arrow keys to move player)
    new_player_x = args.state.player.x
    new_player_y = args.state.player.y
    player_direction = ""
    player_moved = false
    if args.inputs.keyboard.key_down.up
      new_player_y += 1
      player_direction = "north"
      player_moved = true
    elsif args.inputs.keyboard.key_down.down
      new_player_y -= 1
      player_direction = "south"
      player_moved = true
    elsif args.inputs.keyboard.key_down.right
      new_player_x += 1
      player_direction = "east"
      player_moved = true
    elsif args.inputs.keyboard.key_down.left
      new_player_x -= 1
      player_direction = "west"
      player_moved = true
    end
  
    #handle game logic
    # determine if there is an enemy on that square,
    # if so, don't let the player move there
    if player_moved
      found_enemy = args.state.enemies.find do |e|
        e[:x] == new_player_x && e[:y] == new_player_y
      end
  
      if !found_enemy
        args.state.player.x = new_player_x
        args.state.player.y = new_player_y
        args.state.info_message = "You moved #{player_direction}."
      else
        args.state.info_message = "You cannot move into a square an enemy occupies."
      end
    end
  
    args.outputs.sprites << tile_in_game(args.state.player.x,
                                         args.state.player.y, '@')
  
    # render game
    # render enemies at locations
    args.outputs.sprites << args.state.enemies.map do |e|
      tile_in_game(e[:x], e[:y], e[:tile_key])
    end
  
    # render the border
    border_x = args.state.grid.padding - DESTINATION_TILE_SIZE
    border_y = args.state.grid.padding - DESTINATION_TILE_SIZE
    border_size = args.state.grid.size + DESTINATION_TILE_SIZE * 2
  
    args.outputs.borders << [border_x,
                             border_y,
                             border_size,
                             border_size]
  
    # render label stuff
    args.outputs.labels << [border_x, border_y - 10, "Current player location is: #{args.state.player.x}, #{args.state.player.y}"]
    args.outputs.labels << [border_x, border_y + 25 + border_size, args.state.info_message]
  end
  
  def tile_in_game x, y, tile_key
    tile($gtk.args.state.grid.padding + x * DESTINATION_TILE_SIZE,
         $gtk.args.state.grid.padding + y * DESTINATION_TILE_SIZE,
         tile_key)
  end

#+end_src

*** Rpg Roguelike - Roguelike Starting Point - sprite_lookup.rb
#+begin_src ruby
  # ./samples/99_genre_rpg_roguelike/01_roguelike_starting_point/app/sprite_lookup.rb
  def sprite_lookup
    {
      0 => [3, 0],
      1 => [3, 1],
      2 => [3, 2],
      3 => [3, 3],
      4 => [3, 4],
      5 => [3, 5],
      6 => [3, 6],
      7 => [3, 7],
      8 => [3, 8],
      9 => [3, 9],
      '@' => [4, 0],
      A: [ 4,  1],
      B: [ 4,  2],
      C: [ 4,  3],
      D: [ 4,  4],
      E: [ 4,  5],
      F: [ 4,  6],
      G: [ 4,  7],
      H: [ 4,  8],
      I: [ 4,  9],
      J: [ 4, 10],
      K: [ 4, 11],
      L: [ 4, 12],
      M: [ 4, 13],
      N: [ 4, 14],
      O: [ 4, 15],
      P: [ 5,  0],
      Q: [ 5,  1],
      R: [ 5,  2],
      S: [ 5,  3],
      T: [ 5,  4],
      U: [ 5,  5],
      V: [ 5,  6],
      W: [ 5,  7],
      X: [ 5,  8],
      Y: [ 5,  9],
      Z: [ 5, 10],
      a: [ 6,  1],
      b: [ 6,  2],
      c: [ 6,  3],
      d: [ 6,  4],
      e: [ 6,  5],
      f: [ 6,  6],
      g: [ 6,  7],
      h: [ 6,  8],
      i: [ 6,  9],
      j: [ 6, 10],
      k: [ 6, 11],
      l: [ 6, 12],
      m: [ 6, 13],
      n: [ 6, 14],
      o: [ 6, 15],
      p: [ 7,  0],
      q: [ 7,  1],
      r: [ 7,  2],
      s: [ 7,  3],
      t: [ 7,  4],
      u: [ 7,  5],
      v: [ 7,  6],
      w: [ 7,  7],
      x: [ 7,  8],
      y: [ 7,  9],
      z: [ 7, 10],
      '|' => [ 7, 12]
    }
  end
  
  def sprite key
    $gtk.args.state.reserved.sprite_lookup[key]
  end
  
  def member_name_as_code raw_member_name
    if raw_member_name.is_a? Symbol
      ":#{raw_member_name}"
    elsif raw_member_name.is_a? String
      "'#{raw_member_name}'"
    elsif raw_member_name.is_a? Fixnum
      "#{raw_member_name}"
    else
      "UNKNOWN: #{raw_member_name}"
    end
  end
  
  def tile x, y, tile_row_column_or_key
    tile_extended x, y, DESTINATION_TILE_SIZE, DESTINATION_TILE_SIZE, TILE_R, TILE_G, TILE_B, TILE_A, tile_row_column_or_key
  end
  
  def tile_extended x, y, w, h, r, g, b, a, tile_row_column_or_key
    row_or_key, column = tile_row_column_or_key
    if !column
      row, column = sprite row_or_key
    else
      row, column = row_or_key, column
    end
  
    if !row
      member_name = member_name_as_code tile_row_column_or_key
      raise "Unabled to find a sprite for #{member_name}. Make sure the value exists in app/sprite_lookup.rb."
    end
  
    # Sprite provided by Rogue Yun
    # http://www.bay12forums.com/smf/index.php?topic=144897.0
    # License: Public Domain
  
    {
      x: x,
      y: y,
      w: w,
      h: h,
      tile_x: column * 16,
      tile_y: (row * 16),
      tile_w: 16,
      tile_h: 16,
      r: r,
      g: g,
      b: b,
      a: a,
      path: 'sprites/simple-mood-16x16.png'
    }
  end
  
  $gtk.args.state.reserved.sprite_lookup = sprite_lookup

#+end_src

*** Rpg Roguelike - Roguelike Line Of Sight - main.rb
#+begin_src ruby
  # ./samples/99_genre_rpg_roguelike/02_roguelike_line_of_sight/app/main.rb
  =begin
  
   APIs listing that haven't been encountered in previous sample apps:
  
   - lambda: A way to define a block and its parameters with special syntax.
     For example, the syntax of lambda looks like this:
     my_lambda = -> { puts "This is my lambda" }
  
   Reminders:
   - args.outputs.labels: An array. The values generate a label.
     The parameters are [X, Y, TEXT, SIZE, ALIGNMENT, RED, GREEN, BLUE, ALPHA, FONT STYLE]
     For more information about labels, go to mygame/documentation/02-labels.
  
   - ARRAY#inside_rect?: Returns whether or not the point is inside a rect.
  
   - product: Returns an array of all combinations of elements from all arrays.
  
   - find: Finds all elements of a collection that meet requirements.
  
   - abs: Returns the absolute value.
  
  =end
  
  # This sample app allows the player to move around in the dungeon, which becomes more or less visible
  # depending on the player's location, and also has enemies.
  
  class Game
    attr_accessor :args, :state, :inputs, :outputs, :grid
  
    # Calls all the methods needed for the game to run properly.
    def tick
      defaults
      render_canvas
      render_dungeon
      render_player
      render_enemies
      print_cell_coordinates
      calc_canvas
      input_move
      input_click_map
    end
  
    # Sets default values and initializes variables
    def defaults
      outputs.background_color = [0, 0, 0] # black background
  
      # Initializes empty canvas, dungeon, and enemies collections.
      state.canvas   ||= []
      state.dungeon  ||= []
      state.enemies  ||= []
  
      # If state.area doesn't have value, load_area_one and derive_dungeon_from_area methods are called
      if !state.area
        load_area_one
        derive_dungeon_from_area
  
        # Changing these values will change the position of player
        state.x = 7
        state.y = 5
  
        # Creates new enemies, sets their values, and adds them to the enemies collection.
        state.enemies << state.new_entity(:enemy) do |e| # declares each enemy as new entity
          e.x           = 13 # position
          e.y           = 5
          e.previous_hp = 3
          e.hp          = 3
          e.max_hp      = 3
          e.is_dead     = false # the enemy is alive
        end
  
        update_line_of_sight # updates line of sight by adding newly visible cells
      end
    end
  
    # Adds elements into the state.area collection
    # The dungeon is derived using the coordinates of this collection
    def load_area_one
      state.area ||= []
      state.area << [8, 6]
      state.area << [7, 6]
      state.area << [7, 7]
      state.area << [8, 9]
      state.area << [7, 8]
      state.area << [7, 9]
      state.area << [6, 4]
      state.area << [7, 3]
      state.area << [7, 4]
      state.area << [6, 5]
      state.area << [7, 5]
      state.area << [8, 5]
      state.area << [8, 4]
      state.area << [1, 1]
      state.area << [0, 1]
      state.area << [0, 2]
      state.area << [1, 2]
      state.area << [2, 2]
      state.area << [2, 1]
      state.area << [2, 3]
      state.area << [1, 3]
      state.area << [1, 4]
      state.area << [2, 4]
      state.area << [2, 5]
      state.area << [1, 5]
      state.area << [2, 6]
      state.area << [3, 6]
      state.area << [4, 6]
      state.area << [4, 7]
      state.area << [4, 8]
      state.area << [5, 8]
      state.area << [5, 9]
      state.area << [6, 9]
      state.area << [7, 10]
      state.area << [7, 11]
      state.area << [7, 12]
      state.area << [7, 12]
      state.area << [7, 13]
      state.area << [8, 13]
      state.area << [9, 13]
      state.area << [10, 13]
      state.area << [11, 13]
      state.area << [12, 13]
      state.area << [12, 12]
      state.area << [8, 12]
      state.area << [9, 12]
      state.area << [10, 12]
      state.area << [11, 12]
      state.area << [12, 11]
      state.area << [13, 11]
      state.area << [13, 10]
      state.area << [13, 9]
      state.area << [13, 8]
      state.area << [13, 7]
      state.area << [13, 6]
      state.area << [12, 6]
      state.area << [14, 6]
      state.area << [14, 5]
      state.area << [13, 5]
      state.area << [12, 5]
      state.area << [12, 4]
      state.area << [13, 4]
      state.area << [14, 4]
      state.area << [1, 6]
      state.area << [6, 6]
    end
  
    # Starts with an empty dungeon collection, and adds dungeon cells into it.
    def derive_dungeon_from_area
      state.dungeon = [] # starts as empty collection
  
      state.area.each do |a| # for each element of the area collection
        state.dungeon << state.new_entity(:dungeon_cell) do |d| # declares each dungeon cell as new entity
          d.x = a.x # dungeon cell position using coordinates from area
          d.y = a.y
          d.is_visible = false # cell is not visible
          d.alpha = 0 # not transparent at all
          d.border = [left_margin   + a.x * grid_size,
                      bottom_margin + a.y * grid_size,
                      grid_size,
                      grid_size,
                      *blue,
                      255] # sets border definition for dungeon cell
          d # returns dungeon cell
        end
      end
    end
  
    def left_margin
      40  # sets left margin
    end
  
    def bottom_margin
      60 # sets bottom margin
    end
  
    def grid_size
      40 # sets size of grid square
    end
  
    # Updates the line of sight by calling the thick_line_of_sight method and
    # adding dungeon cells to the newly_visible collection
    def update_line_of_sight
      variations = [-1, 0, 1]
      # creates collection of newly visible dungeon cells
      newly_visible = variations.product(variations).flat_map do |rise, run| # combo of all elements
        thick_line_of_sight state.x, state.y, rise, run, 15, # calls thick_line_of_sight method
                            lambda { |x, y| dungeon_cell_exists? x, y } # checks whether or not cell exists
      end.uniq# removes duplicates
  
      state.dungeon.each do |d| # perform action on each element of dungeons collection
        d.is_visible = newly_visible.find { |v| v.x == d.x && v.y == d.y } # finds match inside newly_visible collection
      end
    end
  
    #Returns a boolean value
    def dungeon_cell_exists? x, y
      # Finds cell coordinates inside dungeon collection to determine if dungeon cell exists
      state.dungeon.find { |d| d.x == x && d.y == y }
    end
  
    # Calls line_of_sight method to add elements to result collection
    def thick_line_of_sight start_x, start_y, rise, run, distance, cell_exists_lambda
      result = []
      result += line_of_sight start_x, start_y, rise, run, distance, cell_exists_lambda
      result += line_of_sight start_x - 1, start_y, rise, run, distance, cell_exists_lambda # one left
      result += line_of_sight start_x + 1, start_y, rise, run, distance, cell_exists_lambda # one right
      result
    end
  
    # Adds points to the result collection to create the player's line of sight
    def line_of_sight start_x, start_y, rise, run, distance, cell_exists_lambda
      result = [] # starts as empty collection
      points = points_on_line start_x, start_y, rise, run, distance # calls points_on_line method
      points.each do |p| # for each point in collection
        if cell_exists_lambda.call(p.x, p.y) # if the cell exists
          result << p # add it to result collection
        else # if cell does not exist
          return result # return result collection as it is
        end
      end
  
      result # return result collection
    end
  
    # Finds the coordinates of the points on the line by performing calculations
    def points_on_line start_x, start_y, rise, run, distance
      distance.times.map do |i| # perform an action
        [start_x + run * i, start_y + rise * i] # definition of point
      end
    end
  
    def render_canvas
      return
      outputs.borders << state.canvas.map do |c| # on each element of canvas collection
        c.border # outputs border
      end
    end
  
    # Outputs the dungeon cells.
    def render_dungeon
      outputs.solids << [0, 0, grid.w, grid.h] # outputs black background for grid
  
      # Sets the alpha value (opacity) for each dungeon cell and calls the cell_border method.
      outputs.borders << state.dungeon.map do |d| # for each element in dungeon collection
        d.alpha += if d.is_visible # if cell is visible
                   255.fdiv(30) # increment opacity (transparency)
                 else # if cell is not visible
                   255.fdiv(600) * -1 # decrease opacity
                 end
        d.alpha = d.alpha.cap_min_max(0, 255)
        cell_border d.x, d.y, [*blue, d.alpha] # sets blue border using alpha value
      end.reject_nil
    end
  
    # Sets definition of a cell border using the parameters
    def cell_border x, y, color = nil
      [left_margin   + x * grid_size,
      bottom_margin + y * grid_size,
      grid_size,
      grid_size,
      *color]
    end
  
    # Sets the values for the player and outputs it as a label
    def render_player
      outputs.labels << [grid_x(state.x) + 20, # positions "@" text in center of grid square
                       grid_y(state.y) + 35,
                       "@", # player is represented by a white "@" character
                       1, 1, *white]
    end
  
    def grid_x x
      left_margin + x * grid_size # positions horizontally on grid
    end
  
    def grid_y y
      bottom_margin + y * grid_size # positions vertically on grid
    end
  
    # Outputs enemies onto the screen.
    def render_enemies
      state.enemies.map do |e| # for each enemy in the collection
        alpha = 255 # set opacity (full transparency)
  
        # Outputs an enemy using a label.
        outputs.labels << [
                     left_margin + 20 +  e.x * grid_size, # positions enemy's "r" text in center of grid square
                     bottom_margin + 35 + e.y * grid_size,
                     "r", # enemy's text
                     1, 1, *white, alpha]
  
        # Creates a red border around an enemy.
        outputs.borders << [grid_x(e.x), grid_y(e.y), grid_size, grid_size, *red]
      end
    end
  
    #White labels are output for the cell coordinates of each element in the dungeon collection.
    def print_cell_coordinates
      return unless state.debug
      state.dungeon.each do |d|
        outputs.labels << [grid_x(d.x) + 2,
                           grid_y(d.y) - 2,
                           "#{d.x},#{d.y}",
                           -2, 0, *white]
      end
    end
  
    # Adds new elements into the canvas collection and sets their values.
    def calc_canvas
      return if state.canvas.length > 0 # return if canvas collection has at least one element
      15.times do |x| # 15 times perform an action
        15.times do |y|
          state.canvas << state.new_entity(:canvas) do |c| # declare canvas element as new entity
            c.x = x # set position
            c.y = y
            c.border = [left_margin   + x * grid_size,
                        bottom_margin + y * grid_size,
                        grid_size,
                        grid_size,
                        *white, 30] # sets border definition
          end
        end
      end
    end
  
    # Updates x and y values of the player, and updates player's line of sight
    def input_move
      x, y, x_diff, y_diff = input_target_cell
  
      return unless dungeon_cell_exists? x, y # player can't move there if a dungeon cell doesn't exist in that location
      return if enemy_at x, y # player can't move there if there is an enemy in that location
  
      state.x += x_diff # increments x by x_diff (so player moves left or right)
      state.y += y_diff # same with y and y_diff ( so player moves up or down)
      update_line_of_sight # updates visible cells
    end
  
    def enemy_at x, y
      # Finds if coordinates exist in enemies collection and enemy is not dead
      state.enemies.find { |e| e.x == x && e.y == y && !e.is_dead }
    end
  
    #M oves the user based on their keyboard input and sets values for target cell
    def input_target_cell
      if inputs.keyboard.key_down.up # if "up" key is in "down" state
        [state.x, state.y + 1,  0,  1] # user moves up
      elsif inputs.keyboard.key_down.down # if "down" key is pressed
        [state.x, state.y - 1,  0, -1] # user moves down
      elsif inputs.keyboard.key_down.left # if "left" key is pressed
        [state.x - 1, state.y, -1,  0] # user moves left
      elsif inputs.keyboard.key_down.right # if "right" key is pressed
        [state.x + 1, state.y,  1,  0] # user moves right
      else
        nil  # otherwise, empty
      end
    end
  
    # Goes through the canvas collection to find if the mouse was clicked inside of the borders of an element.
    def input_click_map
      return unless inputs.mouse.click # return unless the mouse is clicked
      canvas_entry = state.canvas.find do |c| # find element from canvas collection that meets requirements
        inputs.mouse.click.inside_rect? c.border # find border that mouse was clicked inside of
      end
      puts canvas_entry # prints canvas_entry value
    end
  
    # Sets the definition of a label using the parameters.
    def label text, x, y, color = nil
      color ||= white # color is initialized to white
      [x, y, text, 1, 1, *color] # sets label definition
    end
  
    def green
      [60, 200, 100] # sets color saturation to shade of green
    end
  
    def blue
      [50, 50, 210] # sets color saturation to shade of blue
    end
  
    def white
      [255, 255, 255] # sets color saturation to white
    end
  
    def red
      [230, 80, 80] # sets color saturation to shade of red
    end
  
    def orange
      [255, 80, 60] # sets color saturation to shade of orange
    end
  
    def pink
      [255, 0, 200] # sets color saturation to shade of pink
    end
  
    def gray
      [75, 75, 75] # sets color saturation to shade of gray
    end
  
    # Recolors the border using the parameters.
    def recolor_border border, r, g, b
      border[4] = r
      border[5] = g
      border[6] = b
      border
    end
  
    # Returns a boolean value.
    def visible? cell
      # finds cell's coordinates inside visible_cells collections to determine if cell is visible
      state.visible_cells.find { |c| c.x == cell.x && c.y == cell.y}
    end
  
    # Exports dungeon by printing dungeon cell coordinates
    def export_dungeon
      state.dungeon.each do |d| # on each element of dungeon collection
        puts "state.dungeon << [#{d.x}, #{d.y}]" # prints cell coordinates
      end
    end
  
    def distance_to_cell cell
      distance_to state.x, cell.x, state.y, cell.y # calls distance_to method
    end
  
    def distance_to from_x, x, from_y, y
      (from_x - x).abs + (from_y - y).abs # finds distance between two cells using coordinates
    end
  end
  
  $game = Game.new
  
  def tick args
    $game.args    = args
    $game.state   = args.state
    $game.inputs  = args.inputs
    $game.outputs = args.outputs
    $game.grid    = args.grid
    $game.tick
  end

#+end_src

*** Rpg Tactical - Hexagonal Grid - main.rb
#+begin_src ruby
  # ./samples/99_genre_rpg_tactical/hexagonal_grid/app/main.rb
  class HexagonTileGame
    attr_gtk
  
    def defaults
      state.tile_scale      = 1.3
      state.tile_size       = 80
      state.tile_w          = Math.sqrt(3) * state.tile_size.half
      state.tile_h          = state.tile_size * 3/4
      state.tiles_x_count   = 1280.idiv(state.tile_w) - 1
      state.tiles_y_count   = 720.idiv(state.tile_h) - 1
      state.world_width_px  = state.tiles_x_count * state.tile_w
      state.world_height_px = state.tiles_y_count * state.tile_h
      state.world_x_offset  = (1280 - state.world_width_px).half
      state.world_y_offset  = (720 - state.world_height_px).half
      state.tiles         ||= state.tiles_x_count.map_with_ys(state.tiles_y_count) do |ordinal_x, ordinal_y|
        {
          ordinal_x: ordinal_x,
          ordinal_y: ordinal_y,
          offset_x: (ordinal_y.even?) ?
                    (state.world_x_offset + state.tile_w.half.half) :
                    (state.world_x_offset - state.tile_w.half.half),
          offset_y: state.world_y_offset,
          w: state.tile_w,
          h: state.tile_h,
          type: :blank,
          path: "sprites/hexagon-gray.png",
          a: 20
        }.associate do |h|
          h.merge(x: h[:offset_x] + h[:ordinal_x] * h[:w],
                  y: h[:offset_y] + h[:ordinal_y] * h[:h]).scale_rect(state.tile_scale)
        end.associate do |h|
          h.merge(center: {
                    x: h[:x] + h[:w].half,
                    y: h[:y] + h[:h].half
                  }, radius: [h[:w].half, h[:h].half].max)
        end
      end
    end
  
    def input
      if inputs.click
        tile = state.tiles.find { |t| inputs.click.point_inside_circle? t[:center], t[:radius] }
        if tile
          tile[:a] = 255
          tile[:path] = "sprites/hexagon-black.png"
        end
      end
    end
  
    def tick
      defaults
      input
      render
    end
  
    def render
      outputs.sprites << state.tiles
    end
  end
  
  $game = HexagonTileGame.new
  
  def tick args
    $game.args = args
    $game.tick
  end
  
  $gtk.reset

#+end_src

*** Rpg Tactical - Isometric Grid - main.rb
#+begin_src ruby
  # ./samples/99_genre_rpg_tactical/isometric_grid/app/main.rb
  class Isometric
      attr_accessor :grid, :inputs, :state, :outputs
  
      def tick
          defaults
          render
          calc
          process_inputs
      end
  
      def defaults
          state.quantity              ||= 6                                                        #Size of grid
          state.tileSize              ||= [262 / 2, 194 / 2]                                       #width and heigth of orange tiles
          state.tileGrid              ||= []                                                       #Holds ordering of tiles
          state.currentSpriteLocation ||= -1                                                       #Current Sprite hovering location 
          state.tileCords             ||= []                                                       #Physical, rendering cordinates
          state.initCords             ||= [640 - (state.quantity / 2 * state.tileSize[0]), 330]    #Location of tile (0, 0)
          state.sideSize              ||= [state.tileSize[0] / 2, 242 / 2]                         #Purple & green cube face size
          state.mode                  ||= :delete                                                  #Switches between :delete and :insert
          state.spriteSelection       ||= [['river',    0, 0, 262 / 2, 194 / 2],
                                           ['mountain', 0, 0, 262 / 2, 245 / 2],
                                           ['ocean',    0, 0, 262 / 2, 194 / 2]]             #Storage for sprite information
                                                                                             #['name', deltaX, deltaY, sizeW, sizeH]
                                                                                             #^delta refers to distance from tile cords
  
          #Orders tiles based on tile placement and fancy math. Very left: 0,0. Very bottom: quantity-1, 0, etc
          if state.tileGrid == []
              tempX = 0
              tempY = 0
              tempLeft = false
              tempRight = false
              count = 0
              (state.quantity * state.quantity).times do
                  if tempY == 0
                      tempLeft = true
                  end
                  if tempX == (state.quantity - 1)
                      tempRight = true
                  end
                  state.tileGrid.push([tempX, tempY, true, tempLeft, tempRight, count])
                      #orderX, orderY, exists?, leftSide, rightSide, order
                  tempX += 1
                  if tempX == state.quantity
                      tempX = 0
                      tempY += 1
                  end
                  tempLeft = false
                  tempRight = false
                  count += 1
              end
          end
  
          #Calculates physical cordinates for tiles
          if state.tileCords == []
              state.tileCords = state.tileGrid.map do
                  |val|
                  x = (state.initCords[0]) + ((val[0] + val[1]) * state.tileSize[0] / 2)
                  y = (state.initCords[1]) + (-1 * val[0] * state.tileSize[1] / 2) + (val[1] * state.tileSize[1] / 2)
                  [x, y, val[2], val[3], val[4], val[5], -1] #-1 represents sprite on top of tile. -1 for now
              end
          end
  
      end
  
      def render
          renderBackground
          renderLeft
          renderRight
          renderTiles
          renderObjects
          renderLabels
      end
  
      def renderBackground
          outputs.solids << [0, 0, 1280, 720, 0, 0, 0]   #Background color
      end
  
      def renderLeft
          #Shows the pink left cube face
          outputs.sprites << state.tileCords.map do
              |val|
              if val[2] == true && val[3] == true       #Checks if the tile exists and right face needs to be rendered
                  [val[0], val[1] + (state.tileSize[1] / 2) - state.sideSize[1], state.sideSize[0],
                  state.sideSize[1], 'sprites/leftSide.png']
              end
          end
      end
  
      def renderRight
          #Shows the green right cube face
          outputs.sprites << state.tileCords.map do
              |val|
              if val[2] == true && val[4] == true        #Checks if it exists & checks if right face needs to be rendered
                  [val[0] + state.tileSize[0] / 2, val[1] + (state.tileSize[1] / 2) - state.sideSize[1], state.sideSize[0],
                  state.sideSize[1], 'sprites/rightSide.png']
              end
          end
      end
  
      def renderTiles
          #Shows the tile itself. Important that it's rendered after the two above!
          outputs.sprites << state.tileCords.map do
              |val|
              if val[2] == true     #Chcekcs if tile needs to be rendered
                if val[5] == state.currentSpriteLocation
                  [val[0], val[1], state.tileSize[0], state.tileSize[1], 'sprites/selectedTile.png']
                else
                  [val[0], val[1], state.tileSize[0], state.tileSize[1], 'sprites/tile.png']
                end
              end
          end
      end
  
      def renderObjects
          #Renders the sprites on top of the tiles. Order of rendering: top corner to right corner and cascade down until left corner
          #to bottom corner.
          a = (state.quantity * state.quantity) - state.quantity
          iter = 0
          loop do
              if state.tileCords[a][2] == true && state.tileCords[a][6] != -1
                  outputs.sprites << [state.tileCords[a][0] + state.spriteSelection[state.tileCords[a][6]][1],
                                      state.tileCords[a][1] + state.spriteSelection[state.tileCords[a][6]][2],
                                      state.spriteSelection[state.tileCords[a][6]][3], state.spriteSelection[state.tileCords[a][6]][4],
                                      'sprites/' + state.spriteSelection[state.tileCords[a][6]][0] + '.png']
              end
              iter += 1
              a    += 1
              a -= state.quantity * 2 if iter == state.quantity
              iter = 0                if iter == state.quantity
              break if a < 0
          end
      end
  
      def renderLabels
          #Labels
          outputs.labels << [50, 680, 'Click to delete!',             5, 0, 255, 255, 255, 255] if state.mode == :delete
          outputs.labels << [50, 640, 'Press \'i\' for insert mode!', 5, 0, 255, 255, 255, 255] if state.mode == :delete
          outputs.labels << [50, 680, 'Click to insert!',             5, 0, 255, 255, 255, 255] if state.mode == :insert
          outputs.labels << [50, 640, 'Press \'d\' for delete mode!', 5, 0, 255, 255, 255, 255] if state.mode == :insert
      end
  
      def calc
          calcCurrentHover
      end
  
      def calcCurrentHover
          #This determines what tile the mouse is hovering (or last hovering) over
          x = inputs.mouse.position.x
          y = inputs.mouse.position.y
          m = (state.tileSize[1] / state.tileSize[0])   #slope
          state.tileCords.map do
              |val|
              #Conditions that makes runtime faster. Checks if the mouse click was between tile dimensions (rectangle collision)
              next unless val[0] < x && x < val[0] + state.tileSize[0]
              next unless val[1] < y && y < val[1] + state.tileSize[1]
              next unless val[2] == true
              tempBool = false
              if x == val[0] + (state.tileSize[0] / 2)
                  #The height of a diamond is the height of the diamond, so if x equals that exact point, it must be inside the diamond
                  tempBool = true
              elsif x < state.tileSize[0] / 2 + val[0]
                  #Uses y = (m) * (x - x1) + y1 to determine the y values for the two diamond lines on the left half of diamond
                  tempY1 =      (m * (x - val[0])) + val[1] + (state.tileSize[1] / 2)
                  tempY2 = (-1 * m * (x - val[0])) + val[1] + (state.tileSize[1] / 2)
                  #Checks to see if the mouse click y value is between those temp y values
                  tempBool = true if y < tempY1 && y > tempY2
              elsif x > state.tileSize[0] / 2 + val[0]
                  #Uses y = (m) * (x - x1) + y1 to determine the y values for the two diamond lines on the right half of diamond
                  tempY1 =      (m * (x - val[0] - (state.tileSize[0] / 2))) + val[1]
                  tempY2 = (-1 * m * (x - val[0] - (state.tileSize[0] / 2))) + val[1] + state.tileSize[1]
                  #Checks to see if the mouse click y value is between those temp y values
                  tempBool = true if y > tempY1 && y < tempY2
              end
  
              if tempBool == true
                  state.currentSpriteLocation = val[5]         #Current sprite location set to the order value
              end
          end
      end
  
      def process_inputs
          #Makes development much faster and easier
          if inputs.keyboard.key_up.r
              $dragon.reset
          end
          checkTileSelected
          switchModes
      end
  
      def checkTileSelected
          if inputs.mouse.down
              x = inputs.mouse.down.point.x
              y = inputs.mouse.down.point.y
              m = (state.tileSize[1] / state.tileSize[0])   #slope
              state.tileCords.map do
                  |val|
                  #Conditions that makes runtime faster. Checks if the mouse click was between tile dimensions (rectangle collision)
                  next unless val[0] < x && x < val[0] + state.tileSize[0]
                  next unless val[1] < y && y < val[1] + state.tileSize[1]
                  next unless val[2] == true
                  tempBool = false
                  if x == val[0] + (state.tileSize[0] / 2)
                      #The height of a diamond is the height of the diamond, so if x equals that exact point, it must be inside the diamond
                      tempBool = true
                  elsif x < state.tileSize[0] / 2 + val[0]
                      #Uses y = (m) * (x - x1) + y1 to determine the y values for the two diamond lines on the left half of diamond
                      tempY1 =      (m * (x - val[0])) + val[1] + (state.tileSize[1] / 2)
                      tempY2 = (-1 * m * (x - val[0])) + val[1] + (state.tileSize[1] / 2)
                      #Checks to see if the mouse click y value is between those temp y values
                      tempBool = true if y < tempY1 && y > tempY2
                  elsif x > state.tileSize[0] / 2 + val[0]
                      #Uses y = (m) * (x - x1) + y1 to determine the y values for the two diamond lines on the right half of diamond
                      tempY1 =      (m * (x - val[0] - (state.tileSize[0] / 2))) + val[1]
                      tempY2 = (-1 * m * (x - val[0] - (state.tileSize[0] / 2))) + val[1] + state.tileSize[1]
                      #Checks to see if the mouse click y value is between those temp y values
                      tempBool = true if y > tempY1 && y < tempY2
                  end
  
                  if tempBool == true
                      if state.mode == :delete
                          val[2] = false
                          state.tileGrid[val[5]][2]  = false      #Unnecessary because never used again but eh, I like consistency
                          state.tileCords[val[5]][2] = false      #Ensures that the tile isn't rendered
                          unless state.tileGrid[val[5]][0] == 0   #If tile is the left most tile in the row, right doesn't get rendered
                              state.tileGrid[val[5] - 1][4] = true            #Why the order value is amazing
                              state.tileCords[val[5] - 1][4] = true
                          end
                          unless state.tileGrid[val[5]][1] == state.quantity - 1     #Same but left side
                              state.tileGrid[val[5] + state.quantity][3] = true
                              state.tileCords[val[5] + state.quantity][3] = true
                          end
                      elsif state.mode == :insert
                          #adds the current sprite value selected to tileCords. (changes from the -1 earlier)
                          val[6] = rand(state.spriteSelection.length)
                      end
                  end
              end
          end
      end
  
      def switchModes
          #Switches between insert and delete modes
          if inputs.keyboard.key_up.i && state.mode == :delete
              state.mode = :insert
              inputs.keyboard.clear
          elsif inputs.keyboard.key_up.d && state.mode == :insert
              state.mode = :delete
              inputs.keyboard.clear
          end
      end
  
  end
  
  $isometric = Isometric.new
  
  def tick args
      $isometric.grid    = args.grid
      $isometric.inputs  = args.inputs
      $isometric.state   = args.state
      $isometric.outputs = args.outputs
      $isometric.tick
  end

#+end_src

*** Rpg Topdown - Topdown Casino - main.rb
#+begin_src ruby
  # ./samples/99_genre_rpg_topdown/topdown_casino/app/main.rb
  $gtk.reset
  
  def coinflip
    rand < 0.5
  end
  
  class Game
    attr_accessor :args
  
    def text_font
      return nil #"rpg.ttf"
    end
  
    def text_color
      [ 255, 255, 255, 255 ]
    end
  
    def set_gem_values
      @args.state.gem0 = ((coinflip) ?  100 : 20)
      @args.state.gem1 = ((coinflip) ? -10 : -50)
      @args.state.gem2 = ((coinflip) ? -10 : -30)
      if coinflip
        tmp = @args.state.gem0
        @args.state.gem0 = @args.state.gem1
        @args.state.gem1 = tmp
      end
      if coinflip
        tmp = @args.state.gem1
        @args.state.gem1 = @args.state.gem2
        @args.state.gem2 = tmp
      end
      if coinflip
        tmp = @args.state.gem0
        @args.state.gem0 = @args.state.gem2
        @args.state.gem2 = tmp
      end
    end
  
    def initialize args
      @args = args
      @args.state.animticks = 0
      @args.state.score = 0
      @args.state.gem_chosen = false
      @args.state.round_finished = false
      @args.state.gem0_x = 197
      @args.state.gem0_y = 720-274
      @args.state.gem1_x = 623
      @args.state.gem1_y = 720-274
      @args.state.gem2_x = 1049
      @args.state.gem2_y = 720-274
      @args.state.hero_sprite = "sprites/herodown100.png"
      @args.state.hero_x = 608
      @args.state.hero_y = 720-656
      set_gem_values
    end
  
    def render_gem_value x, y, gem
      if @args.state.gem_chosen
        @args.outputs.labels << [ x, y + 96, gem.to_s, 1, 1, *text_color, text_font ]
      end
    end
  
    def render
      gemsprite = ((@args.state.animticks % 400) < 200) ? 'sprites/gem200.png' : 'sprites/gem400.png'
      @args.outputs.background_color = [ 0, 0, 0, 255 ]
      @args.outputs.sprites << [608, 720-150, 64, 64, 'sprites/oldman.png']
      @args.outputs.sprites << [300, 720-150, 64, 64, 'sprites/fire.png']
      @args.outputs.sprites << [900, 720-150, 64, 64, 'sprites/fire.png']
      @args.outputs.sprites << [@args.state.gem0_x, @args.state.gem0_y, 32, 64, gemsprite]
      @args.outputs.sprites << [@args.state.gem1_x, @args.state.gem1_y, 32, 64, gemsprite]
      @args.outputs.sprites << [@args.state.gem2_x, @args.state.gem2_y, 32, 64, gemsprite]
      @args.outputs.sprites << [@args.state.hero_x, @args.state.hero_y, 64, 64, @args.state.hero_sprite]
  
      @args.outputs.labels << [ 630, 720-30, "IT'S A SECRET TO EVERYONE.", 1, 1, *text_color, text_font ]
      @args.outputs.labels << [ 50, 720-85, @args.state.score.to_s, 1, 1, *text_color, text_font ]
      render_gem_value @args.state.gem0_x, @args.state.gem0_y, @args.state.gem0
      render_gem_value @args.state.gem1_x, @args.state.gem1_y, @args.state.gem1
      render_gem_value @args.state.gem2_x, @args.state.gem2_y, @args.state.gem2
    end
  
    def calc
      @args.state.animticks += 16
  
      return unless @args.state.gem_chosen
      @args.state.round_finished_debounce ||= 60 * 3
      @args.state.round_finished_debounce -= 1
      return if @args.state.round_finished_debounce > 0
  
      @args.state.gem_chosen = false
      @args.state.hero.sprite[0] = 'sprites/herodown100.png'
      @args.state.hero.sprite[1] = 608
      @args.state.hero.sprite[2] = 656
      @args.state.round_finished_debounce = nil
      set_gem_values
    end
  
    def walk xdir, ydir, anim
      @args.state.hero_sprite = "sprites/#{anim}#{(((@args.state.animticks % 200) < 100) ? '100' : '200')}.png"
      @args.state.hero_x += 5 * xdir
      @args.state.hero_y += 5 * ydir
    end
  
    def check_gem_touching gem_x, gem_y, gem
      return if @args.state.gem_chosen
      herorect = [ @args.state.hero_x, @args.state.hero_y, 64, 64 ]
      return if !herorect.intersect_rect?([gem_x, gem_y, 32, 64])
      @args.state.gem_chosen = true
      @args.state.score += gem
      @args.outputs.sounds << ((gem < 0) ? 'sounds/lose.wav' : 'sounds/win.wav')
    end
  
    def input
      if @args.inputs.keyboard.key_held.left
        walk(-1.0, 0.0, 'heroleft')
      elsif @args.inputs.keyboard.key_held.right
        walk(1.0, 0.0, 'heroright')
      elsif @args.inputs.keyboard.key_held.up
        walk(0.0, 1.0, 'heroup')
      elsif @args.inputs.keyboard.key_held.down
        walk(0.0, -1.0, 'herodown')
      end
  
      check_gem_touching(@args.state.gem0_x, @args.state.gem0_y, @args.state.gem0)
      check_gem_touching(@args.state.gem1_x, @args.state.gem1_y, @args.state.gem1)
      check_gem_touching(@args.state.gem2_x, @args.state.gem2_y, @args.state.gem2)
    end
  
    def tick
      input
      calc
      render
    end
  end
  
  def tick args
      args.state.game ||= Game.new args
      args.state.game.args = args
      args.state.game.tick
  end

#+end_src

*** Rpg Topdown - Topdown Starting Point - main.rb
#+begin_src ruby
  # ./samples/99_genre_rpg_topdown/topdown_starting_point/app/main.rb
  =begin
  
   APIs listing that haven't been encountered in previous sample apps:
  
   - reverse: Returns a new string with the characters from original string in reverse order.
     For example, the command
     "dragonruby".reverse
     would return the string
     "yburnogard".
     Reverse is not only limited to strings, but can be applied to arrays and other collections.
  
   Reminders:
  
   - ARRAY#intersect_rect?: Returns true or false depending on if two rectangles intersect.
  
   - args.outputs.labels: An array. The values generate a label.
     The parameters are [X, Y, TEXT, SIZE, ALIGNMENT, RED, GREEN, BLUE, ALPHA, FONT STYLE]
     For more information about labels, go to mygame/documentation/02-labels.md.
  
  =end
  
  # This code shows a maze and uses input from the keyboard to move the user around the screen.
  # The objective is to reach the goal.
  
  # Sets values of tile size and player's movement speed
  # Also creates tile or box for player and generates map
  def tick args
    args.state.tile_size     = 80
    args.state.player_speed  = 4
    args.state.player      ||= tile(args, 7, 3, 0, 128, 180)
    generate_map args
  
    # Adds walls, goal, and player to args.outputs.solids so they appear on screen
    args.outputs.solids << args.state.walls
    args.outputs.solids << args.state.goal
    args.outputs.solids << args.state.player
  
    # If player's box intersects with goal, a label is output onto the screen
    if args.state.player.intersect_rect? args.state.goal
      args.outputs.labels << [30, 720 - 30, "You're a wizard Harry!!"] # 30 pixels lower than top of screen
    end
  
    move_player args, -1,  0 if args.inputs.keyboard.left # x position decreases by 1 if left key is pressed
    move_player args,  1,  0 if args.inputs.keyboard.right # x position increases by 1 if right key is pressed
    move_player args,  0,  1 if args.inputs.keyboard.up # y position increases by 1 if up is pressed
    move_player args,  0, -1 if args.inputs.keyboard.down # y position decreases by 1 if down is pressed
  end
  
  # Sets position, size, and color of the tile
  def tile args, x, y, *color
    [x * args.state.tile_size, # sets definition for array using method parameters
     y * args.state.tile_size, # multiplying by tile_size sets x and y to correct position using pixel values
     args.state.tile_size,
     args.state.tile_size,
     *color]
  end
  
  # Creates map by adding tiles to the wall, as well as a goal (that the player needs to reach)
  def generate_map args
    return if args.state.area
  
    # Creates the area of the map. There are 9 rows running horizontally across the screen
    # and 16 columns running vertically on the screen. Any spot with a "1" is not
    # open for the player to move into (and is green), and any spot with a "0" is available
    # for the player to move in.
    args.state.area = [
      [1, 1, 1, 1, 1, 1, 1, 0, 0, 1, 1, 1, 1, 1, 1, 1,],
      [1, 1, 1, 2, 1, 1, 1, 0, 0, 1, 1, 1, 1, 1, 1, 1,], # the "2" represents the goal
      [1, 1, 1, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1,],
      [1, 1, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1,],
      [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,],
      [1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1,],
      [1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1,],
      [1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,],
      [1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1 ],
    ].reverse # reverses the order of the area collection
  
    # By reversing the order, the way that the area appears above is how it appears
    # on the screen in the game. If we did not reverse, the map would appear inverted.
  
    #The wall starts off with no tiles.
    args.state.walls = []
  
    # If v is 1, a green tile is added to args.state.walls.
    # If v is 2, a black tile is created as the goal.
    args.state.area.map_2d do |y, x, v|
      if    v == 1
        args.state.walls << tile(args, x, y, 0, 255, 0) # green tile
      elsif v == 2 # notice there is only one "2" above because there is only one single goal
        args.state.goal   = tile(args, x, y, 0,   0, 0) # black tile
      end
    end
  end
  
  # Allows the player to move their box around the screen
  def move_player args, *vector
    box = args.state.player.shift_rect(vector) # box is able to move at an angle
  
    # If the player's box hits a wall, it is not able to move further in that direction
    return if args.state.walls
                  .any_intersect_rect?(box)
  
    # Player's box is able to move at angles (not just the four general directions) fast
    args.state.player =
      args.state.player
          .shift_rect(vector.x * args.state.player_speed, # if we don't multiply by speed, then
                      vector.y * args.state.player_speed) # the box will move extremely slow
  end

#+end_src

*** Simulation - Sand Simulation - main.rb
#+begin_src ruby
  # ./samples/99_genre_simulation/sand_simulation/app/main.rb
  class Elements
    def initialize size
      @size = size
      @max_x_ordinal = 1280.idiv size
      @element_lookup = {}
      @elements = []
    end
  
    def add_element x_ordinal, y_ordinal
      return nil if @element_lookup.dig x_ordinal, y_ordinal
      element = Element.new x_ordinal, y_ordinal, @size
      @elements << element
      rehash_elements
      element
    end
  
    def tick
      fn.each_send @elements, self, :move_element
      rehash_elements
    end
  
    def move_element element
      if below_empty?(element) && element.y_ordinal != 0
        element.move  0, -1
      elsif below_left_empty?(element) && element.y_ordinal != 0 && element.x_ordinal != 0
        element.move -1, -1
      elsif below_right_empty?(element) && element.y_ordinal != 0 && element.x_ordinal != @max_x_ordinal
        element.move  1, -1
      end
    end
  
    def element_count
      @elements.length
    end
  
    def rehash_elements
      @element_lookup.clear
      fn.each_send @elements, self, :rehash_element
    end
  
    def rehash_element element
      @element_lookup[element.x_ordinal] ||= {}
      @element_lookup[element.x_ordinal][element.y_ordinal] = element
    end
  
    def below_empty? e
      return false if e.y_ordinal == 0
      return true  if !@element_lookup[e.x_ordinal]
      return true  if !@element_lookup[e.x_ordinal][e.y_ordinal - 1]
      return false if  @element_lookup[e.x_ordinal][e.y_ordinal - 1]
      return true
    end
  
    def below_left_empty? e
      return false if e.y_ordinal == 0
      return false if e.x_ordinal == 0
      return true  if !@element_lookup[e.x_ordinal - 1]
      return true  if !@element_lookup[e.x_ordinal - 1][e.y_ordinal - 1]
      return false if  @element_lookup[e.x_ordinal - 1][e.y_ordinal - 1]
      return true
    end
  
    def below_right_empty? e
      return false if e.y_ordinal == 0
      return false if e.x_ordinal == 256
      return true  if !@element_lookup[e.x_ordinal + 1]
      return true  if !@element_lookup[e.x_ordinal + 1][e.y_ordinal - 1]
      return false if  @element_lookup[e.x_ordinal + 1][e.y_ordinal - 1]
      return true
    end
  end
  
  class Element
    attr_sprite
    attr :x_ordinal, :y_ordinal
  
    def initialize x_ordinal, y_ordinal, s
      @x_ordinal     = x_ordinal
      @y_ordinal     = y_ordinal
      @s             = s
      @x             = x_ordinal * s
      @y             = y_ordinal * s
      @w             = s
      @h             = s
      @path          = "sprites/sand-element.png"
    end
  
    def draw_override ffi
      ffi.draw_sprite @x, @y, @w, @h, @path
    end
  
    def move dx, dy
      @y_ordinal += dy
      @x_ordinal += dx
      @y = @y_ordinal * @s
      @x = @x_ordinal * @s
    end
  end
  
  def tick args
    args.state.size        ||= 10
    args.state.mouse_state ||= :up
    @elements              ||= Elements.new args.state.size
  
    if args.inputs.mouse.down
      args.state.mouse_state = :held
    elsif args.inputs.mouse.up
      args.state.mouse_state = :released
    end
  
    if args.state.mouse_state == :held
      added = @elements.add_element args.inputs.mouse.x.idiv(args.state.size), args.inputs.mouse.y.idiv(args.state.size)
      args.outputs.static_sprites << added if added
    end
  
    @elements.tick
  
    args.outputs.labels << { x: 30, y: 30.from_top, text: "#{args.gtk.current_framerate.to_sf}" }
    args.outputs.labels << { x: 30, y: 60.from_top, text: "#{@elements.element_count}" }
  end
  
  $gtk.reset
  @elements = nil

#+end_src

*** Teenytiny - Teenytiny Starting Point - main.rb
#+begin_src ruby
  # ./samples/99_genre_teenytiny/teenytiny_starting_point/app/main.rb
  # full documenation is at http://docs.dragonruby.org
  # be sure to come to the discord if you hit any snags: http://discord.dragonruby.org
  def tick args
    # ====================================================
    # initialize default variables
    # ====================================================
  
    # ruby has an operator called ||= which means "only initialize this if it's nil"
    args.state.count_down   ||= 20 * 60 # set the count down to 20 seconds
    # set the initial position of the target
    args.state.target       ||= { x: args.grid.w.half,
                                  y: args.grid.h.half,
                                  w: 20,
                                  h: 20 }
  
    # set the initial position of the player
    args.state.player       ||= { x: 50,
                                  y: 50,
                                  w: 20,
                                  h: 20 }
  
    # set the player movement speed
    args.state.player_speed ||= 5
  
    # set the score
    args.state.score        ||= 0
    args.state.teleports    ||= 3
  
    # set the instructions
    args.state.instructions ||= "Get to the red goal! Use arrow keys to move. Spacebar to teleport (use them carefully)!"
  
    # ====================================================
    # render the game
    # ====================================================
    args.outputs.labels  << { x: args.grid.w.half, y: args.grid.h - 10,
                              text: args.state.instructions,
                              alignment_enum: 1 }
  
    # check if it's game over. if so, then render game over
    # otherwise render the current time left
    if game_over? args
      args.outputs.labels  << { x: args.grid.w.half,
                                y: args.grid.h - 40,
                                text: "game over! (press r to start over)",
                                alignment_enum: 1 }
    else
      args.outputs.labels  << { x: args.grid.w.half,
                                y: args.grid.h - 40,
                                text: "time left: #{(args.state.count_down.idiv 60) + 1}",
                                alignment_enum: 1 }
    end
  
    # render the score
    args.outputs.labels  << { x: args.grid.w.half,
                              y: args.grid.h - 70,
                              text: "score: #{args.state.score}",
                              alignment_enum: 1 }
  
    # render the player with teleport count
    args.outputs.sprites << { x: args.state.player.x,
                              y: args.state.player.y,
                              w: args.state.player.w,
                              h: args.state.player.h,
                              path: 'sprites/square-green.png' }
  
    args.outputs.labels << { x: args.state.player.x + 10,
                             y: args.state.player.y + 40,
                             text: "teleports: #{args.state.teleports}",
                             alignment_enum: 1, size_enum: -2 }
  
    # render the target
    args.outputs.sprites << { x: args.state.target.x,
                              y: args.state.target.y,
                              w: args.state.target.w,
                              h: args.state.target.h,
                              path: 'sprites/square-red.png' }
  
    # ====================================================
    # run simulation
    # ====================================================
  
    # count down calculation
    args.state.count_down -= 1
    args.state.count_down = -1 if args.state.count_down < -1
  
    # ====================================================
    # process player input
    # ====================================================
    # if it isn't game over let them move
    if !game_over? args
      dir_y = 0
      dir_x = 0
  
      # determine the change horizontally
      if args.inputs.keyboard.up
        dir_y += args.state.player_speed
      elsif args.inputs.keyboard.down
        dir_y -= args.state.player_speed
      end
  
      # determine the change vertically
      if args.inputs.keyboard.left
        dir_x -= args.state.player_speed
      elsif args.inputs.keyboard.right
        dir_x += args.state.player_speed
      end
  
      # determine if teleport can be used
      if args.inputs.keyboard.key_down.space && args.state.teleports > 0
        args.state.teleports -= 1
        dir_x *= 20
        dir_y *= 20
      end
  
      # apply change to player
      args.state.player.x += dir_x
      args.state.player.y += dir_y
    else
      # if r is pressed, reset the game
      if args.inputs.keyboard.key_down.r
        $gtk.reset
        return
      end
    end
  
    # ====================================================
    # determine score
    # ====================================================
  
    # calculate new score if the player is at goal
    if !game_over? args
  
      # if the player is at the goal, then move the goal
      if args.state.player.intersect_rect? args.state.target
        # increment the goal
        args.state.score += 1
  
        # move the goal to a random location
        args.state.target = { x: (rand args.grid.w), y: (rand args.grid.h), w: 20, h: 20 }
  
        # make sure the goal is inside the view area
        if args.state.target.x < 0
          args.state.target.x += 20
        elsif args.state.target.x > 1280
          args.state.target.x -= 20
        end
  
        # make sure the goal is inside the view area
        if args.state.target.y < 0
          args.state.target.y += 20
        elsif args.state.target.y > 720
          args.state.target.y -= 20
        end
      end
    end
  end
  
  def game_over? args
    args.state.count_down < 0
  end
  
  $gtk.reset

#+end_src

** OSS
Follows is a source code listing for all files that have been open sourced. This code can be found online at [[https://github.com/DragonRuby/dragonruby-game-toolkit-contrib/]].
*** api.rb
#+begin_src ruby
  # ./dragon/api.rb
  # coding: utf-8
  # Copyright 2019 DragonRuby LLC
  # MIT License
  # api.rb has been released under MIT (*only this file*).
  
  module GTK
    class Api
      def initialize
      end
  
      def get_api_autocomplete args, req
        html = <<-S
  <html>
    <head>
      <meta charset="UTF-8"/>
      <title>DragonRuby Game Toolkit Documentation</title>
      <style>
      pre {
        border: solid 1px silver;
        padding: 10px;
        font-size: 14px;
        white-space: pre-wrap;
        white-space: -moz-pre-wrap;
        white-space: -pre-wrap;
        white-space: -o-pre-wrap;
        word-wrap: break-word;
      }
      </style>
    </head>
    <body>
        <script>
          async function submitForm() {
            const result = await fetch("/dragon/autocomplete/", {
              method: 'POST',
              headers: { 'Content-Type': 'application/json' },
              body: JSON.stringify({ index: document.getElementById("index").value,
                                     text: document.getElementById("text").value }),
            });
            document.getElementById("autocomplete-results").innerHTML = await result.text();
          }
        </script>
        <form>
          <div>index</div>
          <input name="index" id="index" type="text" value="27" />
          <div>code</div>
          <textarea name="text" id="text" rows="30" cols="80">def tick args
    args.state.
  end</textarea>
          <br/>
          <input type="button" value="Get Suggestions" onclick="submitForm();" />
          <span id="success-notification"></span>
        </form>
        <pre id="autocomplete-results">
        </pre>
  
      #{links}
    </body>
  </html>
  S
  
        req.respond 200,
                    html,
                    { 'Content-Type' => 'text/html' }
      end
  
      def post_api_autocomplete args, req
        json  = ($gtk.parse_json req.body)
        index = json["index"].to_i
        text  = json["text"]
        suggestions = args.gtk.suggest_autocompletion index: index, text: text
        list_as_string = suggestions.join("\n")
        req.respond 200, list_as_string, { 'Content-Type' => 'text/plain' }
      end
  
      define_method :links do
        <<-S
      <ul>
        <li><a href="/">Home</a></li>
        <li><a href="/docs.html">Docs</a></li>
        <li><a href="/dragon/control_panel/">Control Panel</a></li>
        <li><a href="/dragon/eval/">Console</a></li>
        <li><a href="/dragon/log/">Logs</a></li>
        <li><a href="/dragon/puts/">Puts</a></li>
        <li><a href="/dragon/code/">Code</a></li>
      </ul>
  S
      end
  
      def get_index args, req
        req.respond 200, <<-S, { 'Content-Type' => 'text/html' }
  <html>
    <head>
      <meta charset="UTF-8"/>
      <title>DragonRuby Game Toolkit Documentation</title>
    </head>
    <body>
      #{links}
    </body>
  </html>
  S
      end
  
      def source_code_links args
        links = args.gtk.reload_list_history.keys.map do |f|
          "<li><a href=\"/dragon/code/edit/?file=#{f}\">#{f}</a></li>"
        end
        <<-S
  <ul>
    #{links.join("\n")}
  </ul>
  S
      end
  
      def get_api_code args, req
        view = <<-S
  <html>
    <head>
      <meta charset="UTF-8"/>
      <title>DragonRuby Game Toolkit Documentation</title>
    </head>
    <body>
      #{source_code_links args}
  
      #{links}
    </body>
  </html>
  S
        req.respond 200,
                    view,
                    { 'Content-Type' => 'text/html' }
      end
  
      def code_edit_view args, file
        view = <<-S
  <html>
    <head>
      <meta charset="UTF-8"/>
      <title>DragonRuby Game Toolkit Documentation</title>
    </head>
    <body>
        <script>
          async function submitForm() {
            const result = await fetch("/dragon/code/update/?file=#{file}", {
              method: 'POST',
              headers: { 'Content-Type': 'application/json' },
              body: JSON.stringify({ code: document.getElementById("code").value }),
            });
            document.getElementById("success-notification").innerHTML = "update successful";
            setTimeout(function() { document.getElementById("success-notification").innerHTML = ""; }, 3000);
          }
        </script>
        <form>
          <div><code>#{file}:</code></div>
          <textarea name="code" id="code" rows="30" cols="80">#{args.gtk.read_file file}</textarea>
          <br/>
          <input type="button" value="Update" onclick="submitForm();" />
          <span id="success-notification"></span>
        </form>
      #{source_code_links args}
  
      #{links}
    </body>
  </html>
  S
      end
  
      def get_api_code_edit args, req
        file = req.uri.split('?').last.gsub("file=", "")
        view = code_edit_view args, file
        req.respond 200,
                    view,
                    { 'Content-Type' => 'text/html' }
      end
  
      def post_api_code_update args, req
        file = req.uri.split('?').last.gsub("file=", "")
        code = ($gtk.parse_json req.body)["code"]
        args.gtk.write_file file, code
        view = code_edit_view args, file
        req.respond 200,
                    view,
                    { 'Content-Type' => 'text/html' }
      end
  
      def get_api_boot args, req
        req.respond 200,
                    args.gtk.read_file("tmp/src_backup/boot.txt"),
                    { 'Content-Type' => 'text/plain' }
      end
  
      def get_api_trace args, req
        req.respond 200,
                    args.gtk.read_file("logs/trace.txt"),
                    { 'Content-Type' => 'text/plain' }
      end
  
      def get_api_log args, req
        req.respond 200,
                    args.gtk.read_file("logs/log.txt"),
                    { 'Content-Type' => 'text/plain' }
      end
  
      def post_api_log args, req
        Log.log req.body
  
        req.respond 200,
                    "ok",
                    { 'Content-Type' => 'text/plain' }
      end
  
      def get_api_puts args, req
        req.respond 200,
                    args.gtk.read_file("logs/puts.txt"),
                    { 'Content-Type' => 'text/plain' }
      end
  
      def get_api_changes args, req
        req.respond 200,
                    args.gtk.read_file("tmp/src_backup/src_backup_changes.txt"),
                    { 'Content-Type' => 'text/plain' }
      end
  
      def get_favicon_ico args, req
        @favicon ||= args.gtk.read_file('docs/favicon.ico')
        req.respond 200, @favicon, { "Content-Type" => 'image/x-icon' }
      end
  
      def get_src_backup args, req
        file_name = req.uri.gsub("/dragon/", "")
        req.respond 200,
                    args.gtk.read_file("tmp/src_backup/#{file_name}"),
                    { 'Content-Type' => 'text/plain' }
      end
  
      def get_not_found args, req
        puts("METHOD: #{req.method}");
        puts("URI: #{req.uri}");
        puts("HEADERS:");
        req.headers.each { |k,v| puts("  #{k}: #{v}") }
        req.respond 404, "not found: #{req.uri}", { }
      end
  
      def get_docs_html args, req
        req.respond 200,
                    args.gtk.read_file("docs/docs.html"),
                    { 'Content-Type' => 'text/html' }
      end
  
      def get_docs_css args, req
        req.respond 200,
                    args.gtk.read_file("docs/docs.css"),
                    { 'Content-Type' => 'text/css' }
      end
  
      def get_docs_search_gif args, req
        req.respond 200,
                    args.gtk.read_file("docs/docs_search.gif"),
                    { 'Content-Type' => 'image/gif' }
      end
  
      def get_src_backup_index_html args, req
        req.respond 200,
                    args.gtk.read_file("/tmp/src_backup/src_backup_index.html"),
                    { 'Content-Type' => 'text/html' }
      end
  
      def get_src_backup_index_txt args, req
        req.respond 200,
                    args.gtk.read_file("/tmp/src_backup/src_backup_index.txt"),
                    { 'Content-Type' => 'text/txt' }
      end
  
      def get_src_backup_css args, req
        req.respond 200,
                    args.gtk.read_file("/tmp/src_backup/src_backup.css"),
                    { 'Content-Type' => 'text/css' }
      end
  
      def get_src_backup_changes_html args, req
        req.respond 200,
                    args.gtk.read_file("/tmp/src_backup/src_backup_changes.html"),
                    { 'Content-Type' => 'text/html' }
      end
  
      def get_src_backup_changes_txt args, req
        req.respond 200,
                    args.gtk.read_file("/tmp/src_backup/src_backup_changes.txt"),
                    { 'Content-Type' => 'text/txt' }
      end
  
      def get_api_eval args, req
        eval_view = <<-S
  <html lang="en">
    <head><title>Eval</title></head>
    <style>
    pre {
      border: solid 1px silver;
      padding: 10px;
      font-size: 14px;
      white-space: pre-wrap;
      white-space: -moz-pre-wrap;
      white-space: -pre-wrap;
      white-space: -o-pre-wrap;
      word-wrap: break-word;
    }
    </style>
    <body>
      <script>
        async function submitForm() {
            const result = await fetch("/dragon/eval/", {
              method: 'POST',
              headers: { 'Content-Type': 'application/json' },
              body: JSON.stringify({ code: document.getElementById("code").value }),
            });
            document.getElementById("eval-result").innerHTML = await result.text();
        }
      </script>
      <form>
        <textarea name="code" id="code" rows="10" cols="80"># write your code here and set $result.\n$result = $gtk.args.state</textarea>
        <br/>
        <input type="button" onclick="submitForm();" value="submit" />
      </form>
      <pre>curl -H "Content-Type: application/json" --data '{ "code": "$result = $args.state" }' -X POST http://localhost:9001/dragon/eval/</pre>
      <div>Eval Result:</div>
      <pre id="eval-result"></pre>
      #{links}
    </body>
  </html>
  S
        req.respond 200,
                    eval_view,
                    { 'Content-Type' => 'text/html' }
      end
  
      def post_api_eval args, req
        if json? req
          code = ($gtk.parse_json req.body)["code"]
          code = code.gsub("$result", "$eval_result")
          Object.new.instance_eval do
            begin
              Kernel.eval code
            rescue Exception => e
              $eval_result = e
            end
          end
        end
  
        req.respond 200,
                    "#{$eval_result || $eval_results || "nil"}",
                    { 'Content-Type' => 'text/plain' }
  
        $eval_result  = nil
        $eval_results = nil
      end
  
      def api_css_string
  
      end
  
      def get_api_console args, req
        html = console_view "# write your code here and set $result.\n$result = $gtk.args.state"
        req.respond 200,
                    html,
                    { 'Content-Type' => 'text/html' }
      end
  
      def control_panel_view
        <<-S
  <html lang="en">
    <head><title>console</title></head>
    <body>
      <script>
        async function submitForm(url) {
          const result = await fetch(url, {
            method: 'POST',
            headers: { 'Content-Type': 'application/json' },
            body: JSON.stringify({}),
          });
          document.getElementById("success-notification").innerHTML = "successful";
          setTimeout(function() { document.getElementById("success-notification").innerHTML = ""; }, 3000);
        }
      </script>
      <form>
        <input type="button" value="Show Console" onclick="submitForm('/dragon/show_console/')" />
      </form>
      <form>
        <input type="button" value="Reset Game" onclick="submitForm('/dragon/reset/');" />
      </form>
      <form>
        <input type="button" value="Record Gameplay" onclick="submitForm('/dragon/record/');" />
      </form>
      <form>
        <input type="button" value="Stop Recording" onclick="submitForm('/dragon/record_stop/');" />
      </form>
      <form>
        <input type="button" value="Replay Recording" onclick="submitForm('/dragon/replay/');" />
      </form>
      <div id="success-notification"></div>
      #{links}
    </body>
  </html>
  S
      end
  
      def get_api_control_panel args, req
        req.respond 200,
                    control_panel_view,
                    { 'Content-Type' => 'text/html' }
      end
  
      def json? req
        req.headers.find { |k, v| k == "Content-Type" && (v.include? "application/json") }
      end
  
      def post_api_reset args, req
        $gtk.reset if json? req
        req.respond 200,
                    control_panel_view,
                    { 'Content-Type' => 'text/html' }
      end
  
      def post_api_record args, req
        $recording.start 100 if json? req
        req.respond 200,
                    control_panel_view,
                    { 'Content-Type' => 'text/html' }
      end
  
      def post_api_record_stop args, req
        $recording.stop 'replay.txt' if json? req
        req.respond 200,
                    control_panel_view,
                    { 'Content-Type' => 'text/html' }
      end
  
      def post_api_replay args, req
        $replay.start 'replay.txt' if json? req
        req.respond 200,
                    control_panel_view,
                    { 'Content-Type' => 'text/html' }
      end
  
      def post_api_show_console args, req
        $gtk.console.show if json? req
        req.respond 200,
                    control_panel_view,
                    { 'Content-Type' => 'text/html' }
      end
  
      def tick args
        args.inputs.http_requests.each do |req|
          match_candidate = { method:                   req.method.downcase.to_sym,
                              uri:                      req.uri,
                              uri_without_query_string: (req.uri.split '?').first,
                              query_string:             (req.uri.split '?').last,
                              has_query_string:         !!(req.uri.split '?').last,
                              has_api_prefix:           (req.uri.start_with? "/dragon"),
                              end_with_rb:              (req.uri.end_with? ".rb"),
                              has_file_extension:       file_extensions.find { |f| req.uri.include? f },
                              has_trailing_slash:       (req.uri.split('?').first.end_with? "/") }
  
          if !match_candidate[:has_file_extension]
            if !match_candidate[:has_trailing_slash]
              match_candidate[:uri] = match_candidate[:uri_without_query_string] + "/"
              if match_candidate[:query_string]
                match_candidate[:uri] += "?#{match_candidate[:query_string]}"
              end
            end
          end
  
          context = { args: args, req: req, match_candidate: match_candidate }
  
          process! context: context, routes: routes
        end
      end
  
      def url_decode args, string
        args.fn.gsub string,
                     '+', " ",
                     '%27',    "'",
                     '%22',    '"',
                     '%0D%0A', "\n",
                     '%3D',    "=",
                     '%3B',    ";",
                     '%7C',    "|",
                     '%28',    "(",
                     '%29',    ")",
                     '%7B',    "{",
                     '%7D',    "}",
                     '%2C',    ",",
                     '%3A',    ":",
                     '%5B',    "[",
                     '%5D',    "]",
                     '%23',    "#",
                     '%21',    "!",
                     '%3C',    "<",
                     '%3E',    ">",
                     '%2B',    "+",
                     '%2F',    "/",
                     '%40',    "@",
                     '%3F',    "?",
                     '%26',    "&",
                     '%24',    "$",
                     '%5C',    "\\",
                     '%60',    "`",
                     '%7E',    "~",
                     '%C2%B2', "²",
                     '%5E',    "^",
                     '%C2%BA', "º",
                     '%C2%A7', "§",
                     '%20',    " ",
                     '%0A',    "\n",
                     '%25',    "%",
                     '%2A',    "*"
      end
  
      def file_extensions
        [".html", ".css", ".gif", ".txt", ".ico", ".rb"]
      end
  
      def routes
        [{ match_criteria: { method: :get, uri: "/" },
           handler:        :get_index },
         { match_criteria: { method: :get, uri: "/dragon/" },
           handler:        :get_index },
  
         { match_criteria: { method: :get, uri: "/dragon/boot/" },
           handler:        :get_api_boot },
         { match_criteria: { method: :get, uri: "/dragon/trace/" },
           handler:        :get_api_trace },
         { match_criteria: { method: :get, uri: "/dragon/puts/" },
           handler:        :get_api_puts },
         { match_criteria: { method: :get, uri: "/dragon/log/" },
           handler:        :get_api_log },
         { match_criteria: { method: :post, uri: "/dragon/log/" },
           handler:        :post_api_log },
         { match_criteria: { method: :get, uri: "/dragon/changes/" },
           handler:        :get_api_changes },
         { match_criteria: { method: :get, uri: "/dragon/eval/" },
           handler:        :get_api_eval },
         { match_criteria: { method: :post, uri: "/dragon/eval/" },
           handler:        :post_api_eval },
         { match_criteria: { method: :get, uri: "/dragon/console/" },
           handler:        :get_api_console },
         { match_criteria: { method: :post, uri: "/dragon/console/" },
           handler:        :post_api_console },
         { match_criteria: { method: :get, uri: "/dragon/control_panel/" },
           handler:        :get_api_control_panel },
         { match_criteria: { method: :post, uri: "/dragon/reset/" },
           handler:        :post_api_reset },
         { match_criteria: { method: :post, uri: "/dragon/record/" },
           handler:        :post_api_record },
         { match_criteria: { method: :post, uri: "/dragon/record_stop/" },
           handler:        :post_api_record_stop },
         { match_criteria: { method: :post, uri: "/dragon/replay/" },
           handler:        :post_api_replay },
         { match_criteria: { method: :post, uri: "/dragon/show_console/" },
           handler:        :post_api_show_console },
         { match_criteria: { method: :get, uri: "/dragon/code/" },
           handler:        :get_api_code },
         { match_criteria: { method: :get, uri: "/dragon/autocomplete/" },
           handler:        :get_api_autocomplete },
         { match_criteria: { method: :post, uri: "/dragon/autocomplete/" },
           handler:        :post_api_autocomplete },
         { match_criteria: { method: :get, uri_without_query_string: "/dragon/code/edit/", has_query_string: true },
           handler:        :get_api_code_edit },
         { match_criteria: { method: :post, uri_without_query_string: "/dragon/code/update/", has_query_string: true },
           handler:        :post_api_code_update },
  
  
         { match_criteria: { method: :get, uri: "/docs.html" },
           handler:        :get_docs_html },
         { match_criteria: { method: :get, uri_without_query_string: "/docs.css" },
           handler:        :get_docs_css },
         { match_criteria: { method: :get, uri: "/docs_search.gif" },
           handler:        :get_docs_search_gif },
  
         { match_criteria: { method: :get, uri: "/src_backup_index.html" },
           handler:        :get_src_backup_index_html },
  
         { match_criteria: { method: :get, uri: "/src_backup_index.txt" },
           handler:        :get_src_backup_index_txt },
  
         { match_criteria: { method: :get, uri: "/src_backup_changes.html" },
           handler:        :get_src_backup_changes_html },
  
         { match_criteria: { method: :get, uri: "/src_backup_changes.txt" },
           handler:        :get_src_backup_changes_txt },
  
         { match_criteria: { method: :get, uri: "/src_backup.css" },
           handler:        :get_src_backup_css },
  
         { match_criteria: { method: :get, uri: "/favicon.ico" },
           handler:        :get_favicon_ico },
  
         { match_criteria: { method: :get, end_with_rb: true },
           handler:        :get_src_backup },
  
         { match_criteria: { method: :get, end_with_rb: true },
           handler:        :get_src_backup }
  
        ]
      end
  
      def process! opts
        routes  = opts[:routes]
        context = opts[:context]
        routes.each do |route|
          match_found = (process_single! route: route, context: context)
          return if match_found
        end
      end
  
      def process_single! opts
        match_criteria  = opts[:route][:match_criteria]
        m               = opts[:route][:handler]
        args            = opts[:context][:args]
        req             = opts[:context][:req]
        match_candidate = opts[:context][:match_candidate]
        match_criteria.each do |k, v|
          return false if match_candidate[k] != v
        end
  
        begin
          send m, args, req
        rescue Exception => e
          req.respond 200,
                      "#{e}\n#{e.__backtrace_to_org__}",
                      { 'Content-Type' => 'text/plain' }
        end
        return true
      end
    end
  end

#+end_src

*** args.rb
#+begin_src ruby
  # ./dragon/args.rb
  # coding: utf-8
  # Copyright 2019 DragonRuby LLC
  # MIT License
  # args.rb has been released under MIT (*only this file*).
  
  module GTK
    # This class is the one you'll interact with the most. It's
    # constructed by the DragonRuby Runtime and is provided to you on
    # each tick.
    class Args
      include ArgsDeprecated
      include Serialize
      attr_accessor :cvars
      attr_accessor :inputs
      attr_accessor :outputs
      attr_accessor :audio
      attr_accessor :grid
      attr_accessor :recording
      attr_accessor :geometry
      attr_accessor :fn
      attr_accessor :state
      attr_accessor :temp_state
      attr_accessor :runtime
      alias_method :gtk, :runtime
      attr_accessor :passes
      attr_accessor :wizards
      attr_accessor :layout
      attr_accessor :easing
      attr_accessor :string
  
      def initialize runtime, recording
        @inputs = Inputs.new
        @outputs = Outputs.new args: self
        @cvars = {}
        @audio = {}
        @passes = []
        @state = OpenEntity.new
        @temp_state = OpenEntity.new
        @state.tick_count = -1
        @runtime = runtime
        @recording = recording
        @grid = Grid.new runtime
        @render_targets = {}
        @pixel_arrays = {}
        @all_tests = []
        @geometry = GTK::Geometry
        @fn = GTK::Fn
        @wizards = Wizards.new
        @layout = GTK::Layout.new @grid.w, @grid.h
        @easing = GTK::Easing
        @string = String
      end
  
  
      # The number of ticks since the start of the game.
      #
      # @return [Integer]
      def tick_count
        @state.tick_count
      end
  
      def tick_count= value
        @state.tick_count = value
      end
  
      def serialize
        {
          state:      state.as_hash,
          temp_state: temp_state.as_hash,
          inputs:     inputs.serialize,
          passes:     passes.serialize,
          outputs:    outputs.serialize,
          grid:       grid.serialize
        }
      end
  
      def destructure
        [grid, inputs, state, outputs, runtime, passes]
      end
  
      def clear_pixel_arrays
        pixel_arrays_clear
      end
  
      def pixel_arrays_clear
        @pixel_arrays = {}
      end
  
      def pixel_arrays
        @pixel_arrays
      end
  
      def pixel_array name
        name = name.to_s
        if !@pixel_arrays[name]
          @pixel_arrays[name] = PixelArray.new
        end
        @pixel_arrays[name]
      end
  
      def clear_render_targets
        render_targets_clear
      end
  
      def render_targets_clear
        @render_targets = {}
      end
  
      def render_targets
        @render_targets
      end
  
      def render_target name
        name = name.to_s
        if !@render_targets[name]
          @render_targets[name] = Outputs.new(args: self, target: name, background_color_override: [255, 255, 255, 0])
          @passes << @render_targets[name]
        end
        @render_targets[name]
      end
  
      def solids
        @outputs.solids
      end
  
      def static_solids
        @outputs.static_solids
      end
  
      def sprites
        @outputs.sprites
      end
  
      def static_sprites
        @outputs.static_sprites
      end
  
      def labels
        @outputs.labels
      end
  
      def static_labels
        @outputs.static_labels
      end
  
      def lines
        @outputs.lines
      end
  
      def static_lines
        @outputs.static_lines
      end
  
      def borders
        @outputs.borders
      end
  
      def static_borders
        @outputs.static_borders
      end
  
      def primitives
        @outputs.primitives
      end
  
      def static_primitives
        @outputs.static_primitives
      end
  
      def keyboard
        @inputs.keyboard
      end
  
      def click
        return nil unless @inputs.mouse.click
  
        @inputs.mouse.click.point
      end
  
      def click_at
        return nil unless @inputs.mouse.click
  
        @inputs.mouse.click.created_at
      end
  
      def mouse
        @inputs.mouse
      end
  
      # @see Inputs#controller_one
      # @return (see Inputs#controller_one)
      def controller_one
        @inputs.controller_one
      end
  
      # @see Inputs#controller_two
      # @return (see Inputs#controller_two)
      def controller_two
        @inputs.controller_two
      end
  
      def autocomplete_methods
        [:inputs, :outputs, :gtk, :state, :geometry, :audio, :grid, :layout, :fn]
      end
  
      def method_missing name, *args, &block
        if (args.length <= 1) && (@state.as_hash.key? name)
          raise <<-S
  * ERROR - :#{name} method missing on ~#{self.class.name}~.
  The method
    :#{name}
  with args
    #{args}
  doesn't exist on #{inspect}.
  ** POSSIBLE SOLUTION - ~args.state.#{name}~ exists.
  Did you forget ~.state~ before ~.#{name}~?
  S
        end
  
        super
      end
    end
  end

#+end_src

*** assert.rb
#+begin_src ruby
  # ./dragon/assert.rb
  # coding: utf-8
  # Copyright 2019 DragonRuby LLC
  # MIT License
  # assert.rb has been released under MIT (*only this file*).
  
  module GTK
  =begin
  This is a tiny assertion api for the unit testing portion of Game Toolkit.
  
  @example
  
  1. Create a file called tests.rb under mygame.
  2. Any method that begins with the word test_ will be considered a test.
  
  def test_this_works args, assert
    assert.equal! 1, 1
  end
  
  3. To run a test, save the file while the game is running.
  
  @example
  
  To add an assertion open up this class and write:
  
  class Assert
    def custom_assertion actual, expected, message = nil
      # this tells Game Toolkit that an assertion was performed (so that the test isn't marked inconclusive).
      @assertion_performed = true
  
      # perform your custom logic here and raise an exception to denote a failure.
  
      raise "Some Error. #{message}."
    end
  end
  =end
    class Assert
      attr :assertion_performed
  
  =begin
  Use this if you are throwing your own exceptions and you want to mark the tests as ran (so that it wont be marked as inconclusive).
  =end
      def ok!
        @assertion_performed = true
      end
  
  =begin
  Assert if a value is a truthy value. All assert methods take an optional final parameter that is the message to display to the user.
  
  @example
  
  def test_does_this_work args, assert
    some_result = Person.new
    assert.true! some_result
    # OR
    assert.true! some_result, "Person was not created."
  end
  =end
      def true! value, message = nil
        @assertion_performed = true
        if !value
          message = "#{value} was not truthy.\n#{message}"
          raise "#{message}"
        end
        nil
      end
  
  =begin
  Assert if a value is a falsey value.
  
  @example
  
  def test_does_this_work args, assert
    some_result = nil
    assert.false! some_result
  end
  =end
      def false! value, message = nil
        @assertion_performed = true
        if value
          message = "#{value} was not falsey.\n#{message}"
          raise message
        end
        nil
      end
  
  =begin
  Assert if two values are equal.
  
  @example
  
  def test_does_this_work args, assert
    a = 1
    b = 1
    assert.equal! a, b
  end
  =end
      def equal! actual, expected, message = nil
        @assertion_performed = true
        if actual != expected
          actual_string = "#{actual}#{actual.nil? ? " (nil) " : " " }".strip
          message = "actual:\n#{actual_string}\n\ndid not equal\n\nexpected:\n#{expected}\n#{message}"
          raise message
        end
        nil
      end
  
      def not_equal! actual, expected, message = nil
        @assertion_performed = true
        if actual == expected
          actual_string = "#{actual}#{actual.nil? ? " (nil) " : " " }".strip
          message = "actual:\n#{actual_string}\n\nequaled\n\nexpected:\n#{expected}\n#{message}"
          raise message
        end
        nil
      end
  
  =begin
  Assert if a value is explicitly nil (not false).
  
  @example
  
  def test_does_this_work args, assert
    a = nil
    b = false
    assert.nil! a # this will pass
    assert.nil! b # this will throw an exception.
  end
  =end
      def nil! value, message = nil
        @assertion_performed = true
        if !value.nil?
          message = "#{value} was supposed to be nil, but wasn't.\n#{message}"
          raise message
        end
        nil
      end
    end
  end

#+end_src

*** attr_gtk.rb
#+begin_src ruby
  # ./dragon/attr_gtk.rb
  # coding: utf-8
  # Copyright 2019 DragonRuby LLC
  # MIT License
  # attr_gtk.rb has been released under MIT (*only this file*).
  
  # @private
  module AttrGTK
    attr_accessor :args
  
    def keyboard
      args.inputs.keyboard
    end
  
    def grid
      args.grid
    end
  
    def state
      args.state
    end
  
    def temp_state
      args.temp_state
    end
  
    def inputs
      args.inputs
    end
  
    def outputs
      args.outputs
    end
  
    def gtk
      args.gtk
    end
  
    def passes
      args.passes
    end
  
    def pixel_arrays
      args.pixel_arrays
    end
  
    def geometry
      args.geometry
    end
  
    def layout
      args.layout
    end
  
    def new_entity entity_type, init_hash = nil, &block
      args.state.new_entity entity_type, init_hash, &block
    end
  
    def new_entity_strict entity_type, init_hash = nil, &block
      args.state.new_entity_strict entity_type, init_hash, &block
    end
  end

#+end_src

*** attr_sprite.rb
#+begin_src ruby
  # ./dragon/attr_sprite.rb
  # coding: utf-8
  # Copyright 2019 DragonRuby LLC
  # MIT License
  # attr_sprite.rb has been released under MIT (*only this file*).
  
  # @private
  module AttrRect
    include GTK::Geometry
  
    def left
      (@x || self.x)
    end
  
    def right
      (@x || self.x) + (@w || self.w)
    end
  
    def bottom
      (@y || self.y)
    end
  
    def top
      (@y || self.y) + (@h || self.h)
    end
  
    def x1
      (@x || self.x)
    end
  
    def y1
      (@y || self.y)
    end
  end
  
  module AttrSprite
    include AttrRect
  
    attr_accessor :x, :y, :w, :h, :path, :angle, :a, :r, :g, :b, :tile_x,
                  :tile_y, :tile_w, :tile_h, :flip_horizontally,
                  :flip_vertically, :angle_anchor_x, :angle_anchor_y, :id,
                  :angle_x, :angle_y, :z,
                  :source_x, :source_y, :source_w, :source_h, :blendmode_enum,
                  :source_x2, :source_y2, :source_x3, :source_y3, :x2, :y2, :x3, :y3
  
    def primitive_marker
      :sprite
    end
  
    def sprite
      self
    end
  
    def x1= value
      @x = value
    end
  
    def y1= value
      @y = value
    end
  end

#+end_src

*** console.rb
#+begin_src ruby
  # ./dragon/console.rb
  # coding: utf-8
  # Copyright 2019 DragonRuby LLC
  # MIT License
  # console.rb has been released under MIT (*only this file*).
  
  # Contributors outside of DragonRuby who also hold Copyright:
  # - Kevin Fischer: https://github.com/kfischer-okarin
  
  module GTK
    class Console
      include ConsoleDeprecated
  
      attr_accessor :show_reason, :log, :logo,
                    :animation_duration,
                    :max_log_lines, :max_history, :log,
                    :last_command_errored, :last_command, :shown_at,
                    :archived_log, :last_log_lines, :last_log_lines_count,
                    :suppress_left_arrow_behavior, :command_set_at,
                    :toast_ids, :bottom,
                    :font_style, :menu,
                    :background_color, :spam_color, :text_color, :warn_color,
                    :error_color, :header_color, :code_color, :comment_color,
                    :debug_color, :unfiltered_color
  
      def initialize
        @font_style = FontStyle.new(font: 'font.ttf', size_enum: -1.5, line_height: 1.1)
        @menu = Menu.new self
        @disabled = false
        @log_offset = 0
        @visible = false
        @toast_ids = []
        @archived_log = []
        @log = [ 'Console ready.' ]
        @max_log_lines = 1000  # I guess...?
        @max_history = 1000  # I guess...?
        @log_invocation_count = 0
        @command_history = []
        @command_history_index = -1
        @nonhistory_input = ''
        @logo = 'console-logo.png'
        @history_fname = 'logs/console_history.txt'
        @background_color = Color.new [0, 0, 0, 224]
        @header_color = Color.new [100, 200, 220]
        @code_color = Color.new [210, 168, 255]
        @comment_color = Color.new [0, 200, 100]
        @animation_duration = 1.seconds
        @shown_at = -1
  
        # these are the colors for text at various log levels.
        @spam_color = Color.new [160, 160, 160]
        @debug_color = Color.new [0, 255, 0]
        @text_color = Color.new [255, 255, 255]
        @warn_color = Color.new [255, 255, 0]
        @error_color = Color.new [200, 50, 50]
        @unfiltered_color = Color.new [0, 255, 255]
  
        load_history
      end
  
      def console_text_width
        @console_text_width ||= ($gtk.logical_width - 20).idiv(font_style.letter_size.x)
      end
  
      def save_history
        $gtk.ffi_file.write_root @history_fname, (@command_history.reverse.join "\n")
      end
  
      def load_history
        @command_history.clear
        str = $gtk.ffi_file.read @history_fname
        return if str.nil?  # no history to load.
  
        str.chomp!("\n")  # Don't let endlines at the end cause extra blank line.
        str.chomp!("\r")
        str.each_line { |s|
          s.chomp!("\n")
          s.chomp!("\r")
          if s.length > 0
            @command_history.unshift s
            break if @command_history.length >= @max_history
          end
        }
  
        @command_history.uniq!
      end
  
      def disable
        @disabled = true
      end
  
      def enable
        @disabled = false
      end
  
      def add_sprite obj
        @log_invocation_count += 1
        obj[:id] ||= "id_#{obj[:path]}_#{Time.now.to_i}".to_sym
  
        if @last_line_log_index &&
           @last_sprite_line.is_a?(Hash) &&
           @last_sprite_line[:id] == obj[:id]
  
          @log[@last_line_log_index] = obj
          return
        end
  
        @log << obj
        @last_line_log_index = @log.length - 1
        @last_sprite_line = obj
        nil
      end
  
      def add_primitive obj
        if obj.is_a? Hash
          add_sprite obj
        else
          add_text obj
        end
        nil
      end
  
      def add_text obj, loglevel=-1
        # loglevel is one of the values of LogLevel in logging.h, or -1 to say "we don't care, colorize it with your special string parsing magic"
        loglevel = -1 if loglevel < 0
        loglevel = 5 if loglevel > 5  # 5 == unfiltered (it's 0x7FFFFFFE in C, clamp it down)
        loglevel = 2 if (loglevel == -1) && obj.start_with?('!c!')  # oh well
        colorstr = (loglevel != -1) ? "!c!#{loglevel}" : nil
  
        @last_log_lines_count ||= 1
        @log_invocation_count += 1
  
        str = obj.to_s
  
        log_lines = []
  
        str.each_line do |s|
          if colorstr.nil?
            s.wrapped_lines(self.console_text_width).each do |l|
              log_lines << l
            end
          else
            s.wrapped_lines(self.console_text_width).each do |l|
              log_lines << "#{colorstr}#{l}"
            end
          end
        end
  
        if log_lines == @last_log_lines && log_lines.length != 0
          @last_log_lines_count += 1
          new_log_line_with_count = @last_log_lines.last + " (#{@last_log_lines_count})"
          if log_lines.length > 1
            @log = @log[0..-(@log.length - log_lines.length)] + log_lines[0..-2] + [new_log_line_with_count]
          else
            @log = @log[0..-2] + [new_log_line_with_count]
          end
          return
        end
  
        log_lines.each do |l|
          @log.shift if @log.length > @max_log_lines
          @log << l
        end
  
        @last_log_lines_count = 1
        @last_log_lines = log_lines
        nil
      end
  
      def ready?
        visible? && @toggled_at.elapsed?(@animation_duration, Kernel.global_tick_count)
      end
  
      def hidden?
        !@visible
      end
  
      def visible?
        @visible
      end
  
      def open reason = nil
        show reason
      end
  
      def show reason = nil
        @shown_at = Kernel.global_tick_count
        @show_reason = reason
        toggle if hidden?
      end
  
      # @gtk
      def hide
        if visible?
          toggle
          @archived_log += @log
          if @archived_log.length > @max_log_lines
            @archived_log = @archived_log.drop(@archived_log.length - @max_log_lines)
          end
          @log.clear
          @show_reason = nil
          clear_toast
        end
      end
  
      def close
        hide
      end
  
      def clear_toast
        @toasted_at = nil
        @toast_duration = 0
      end
  
      def toggle
        @visible = !@visible
        @toggled_at = Kernel.global_tick_count
      end
  
      def currently_toasting?
        return false if hidden?
        return false unless @show_reason == :toast
        return false unless @toasted_at
        return false if @toasted_at.elapsed?(5.seconds, Kernel.global_tick_count)
        return true
      end
  
      def toast_extended id = nil, duration = nil, *messages
        if !id.is_a?(Symbol)
          raise <<-S
  * ERROR:
  args.gtk.console.toast has the following signature:
  
    def toast id, *messages
    end
  
  The id property uniquely defines the message and must be
  a symbol.
  
  After that, you can provide all the objects you want to
  look at.
  
  Example:
  
    args.gtk.console.toast :say_hello,
                              \"Hello world.\",
                              args.state.tick_count
  
  Toast messages autohide after 5 seconds.
  
  If you need to look at something for longer, use
  args.gtk.console.perma_toast instead (which you can manually dismiss).
  
  S
        end
  
        return if currently_toasting?
        return if @toast_ids.include? id
        @toasted_at = Kernel.global_tick_count
        log_once_info :perma_toast_tip, "Use console.perma_toast to show the toast for longer."
        dwim_duration = 5.seconds
        add_text "* toast :#{id}"
        puts "* TOAST: :#{id}"
        messages.each do |message|
          lines = message.to_s.wrapped_lines(self.console_text_width)
          dwim_duration += lines.length.seconds
          add_text "** #{message}"
          puts "** #{message}"
        end
        show :toast
        @toast_duration += duration || dwim_duration
        @toast_ids << id
        set_command "$gtk.console.hide"
      end
  
      def perma_toast id = nil, messages
        toast_extended id, 600.seconds, *messages
      end
  
      def toast id = nil, *messages
        toast_extended id, nil, *messages
      end
  
      def console_toggle_keys
        [
          :backtick!,
          :tilde!,
          :superscript_two!,
          :section_sign!,
          :ordinal_indicator!,
          :circumflex!,
        ]
      end
  
      def console_toggle_key_down? args
        args.inputs.keyboard.key_down.any? console_toggle_keys
      end
  
      def try_search_docs exception
        string_e = "#{exception}"
        @last_command_errored = true
  
        if (string_e.include? "wrong number of arguments")
          method_name = ((string_e.split ":")[0].gsub "'", "")
          if !(method_name.include? " ")
            results = (Kernel.__docs_search_results__ method_name)
            if !results.include? "* DOCS: No results found."
              puts (results.join "\n")
              puts <<-S
  * INFO: #{results.length} matches(s) found in DOCS for ~#{method_name}~ (see above).
  You can search the documentation yourself using the following command in the Console:
  #+begin_src ruby
    docs_search \"#{method_name}\"
  #+end_src
  S
              log_once_info :exported_search_results, "The search results above has been seen in logs/puts.txt and docs/search_results.txt."
            end
          end
        end
      rescue Exception => se
        puts <<-S
  * FATAL: ~GTK::Console#try_search_docs~
  There was an exception searching for docs (~GTK::Console#try_search_docs~). You might want to let DragonRuby know about this.
  ** INNER EXCEPTION
  #{se}
  S
      end
  
      def eval_the_set_command
        cmd = current_input_str.strip
        if cmd.length != 0
          @log_offset = 0
          prompt.clear
  
          @command_history.pop while @command_history.length >= @max_history
          @command_history.unshift cmd
          @command_history_index = -1
          @nonhistory_input = ''
  
          if cmd == 'quit' || cmd == ':wq' || cmd == ':q!' || cmd == ':q' || cmd == ':wqa'
            $gtk.request_quit
          elsif cmd.start_with? ':'
            send ((cmd.gsub '-', '_').gsub ':', '')
          else
            puts "-> #{cmd}"
            begin
              @last_command = cmd
              Kernel.eval("$results = (#{cmd})")
              if $results.nil?
                puts "=> nil"
              elsif $results == :console_silent_eval
                # do nothing since the console is silent
              else
                puts "=> #{$results}"
              end
              @last_command_errored = false
            rescue Exception => e
              try_search_docs e
              # if an exception is thrown and the bactrace includes something helpful, then show it
              if (e.backtrace || []).first && (e.backtrace.first.include? "(eval)")
                puts  "* EXCEPTION: #{e}"
              else
                puts  "* EXCEPTION: #{e}\n#{e.__backtrace_to_org__}"
              end
            end
          end
        end
      end
  
      def inputs_scroll_up_full? args
        return false if @disabled
        args.inputs.keyboard.key_down.pageup ||
          (args.inputs.keyboard.key_up.b && args.inputs.keyboard.key_up.control)
      end
  
      def scroll_to_bottom
        @log_offset = 0
      end
  
      def scroll_up_full
        @log_offset += lines_on_one_page
        @log_offset = @log.size if @log_offset > @log.size
      end
  
      def inputs_scroll_up_half? args
        return false if @disabled
        args.inputs.keyboard.ctrl_u
      end
  
      def scroll_up_half
        @log_offset += lines_on_one_page.idiv(2)
        @log_offset = @log.size if @log_offset > @log.size
      end
  
      def inputs_scroll_down_full? args
        return false if @disabled
        args.inputs.keyboard.key_down.pagedown ||
          (args.inputs.keyboard.key_up.f && args.inputs.keyboard.key_up.control)
      end
  
      def scroll_down_full
        @log_offset -= lines_on_one_page
        @log_offset = 0 if @log_offset < 0
      end
  
      def inputs_scroll_down_half? args
        return false if @disabled
        args.inputs.keyboard.ctrl_d
      end
  
      def inputs_clear_command? args
        return false if @disabled
        args.inputs.keyboard.escape || args.inputs.keyboard.ctrl_g
      end
  
      def scroll_down_half
        @log_offset -= lines_on_one_page.idiv(2)
        @log_offset = 0 if @log_offset < 0
      end
  
      def mouse_wheel_scroll args
        @inertia ||= 0
  
        if args.inputs.mouse.wheel
          if args.inputs.mouse.wheel.y > 0
            @inertia = 1
          elsif args.inputs.mouse.wheel.y < 0
            @inertia = -1
          end
        end
  
        if args.inputs.mouse.click
          @inertia = 0
        end
  
        return if @inertia == 0
  
        @inertia = (@inertia * 0.7)
        if @inertia > 0
          @log_offset += 1
        elsif @inertia < 0
          @log_offset -= 1
        end
  
        if @inertia.abs < 0.01
          @inertia = 0
        end
  
        if @log_offset > @log.size
          @log_offset = @log.size
        elsif @log_offset < 0
          @log_offset = 0
        end
      end
  
      def process_inputs args
        if console_toggle_key_down? args
          args.inputs.text.clear
          toggle
          args.inputs.keyboard.clear if !@visible
        end
  
        return unless visible?
  
        args.inputs.text.each { |str| prompt << str }
        args.inputs.text.clear
        mouse_wheel_scroll args
  
        @log_offset = 0 if @log_offset < 0
  
        if args.inputs.keyboard.key_down.enter
          if slide_progress > 0.5
            # in the event of an exception, the console window pops up
            # and is pre-filled with $gtk.reset.
            # there is an annoying scenario where the exception could be thrown
            # by pressing enter (while playing the game). if you press enter again
            # quickly, then the game is reset which closes the console.
            # so enter in the console is only evaluated if the slide_progress
            # is atleast half way down the page.
            eval_the_set_command
          end
        elsif args.inputs.keyboard.key_down.v
          if args.inputs.keyboard.key_down.control || args.inputs.keyboard.key_down.meta
            prompt << $gtk.ffi_misc.getclipboard
          end
        elsif args.inputs.keyboard.key_down.home
          prompt.move_cursor_home
        elsif args.inputs.keyboard.key_down.end
          prompt.move_cursor_end
        elsif args.inputs.keyboard.key_down.up
          if @command_history_index == -1
            @nonhistory_input = current_input_str
          end
          if @command_history_index < (@command_history.length - 1)
            @command_history_index += 1
            self.current_input_str = @command_history[@command_history_index].dup
          end
        elsif args.inputs.keyboard.key_down.down
          if @command_history_index == 0
            @command_history_index = -1
            self.current_input_str = @nonhistory_input
            @nonhistory_input = ''
          elsif @command_history_index > 0
            @command_history_index -= 1
            self.current_input_str = @command_history[@command_history_index].dup
          end
        elsif args.inputs.keyboard.key_down.left
          if args.inputs.keyboard.key_down.control
            prompt.move_cursor_left_word
          else
            prompt.move_cursor_left
          end
        elsif args.inputs.keyboard.key_down.right
          if args.inputs.keyboard.key_down.control
            prompt.move_cursor_right_word
          else
            prompt.move_cursor_right
          end
        elsif inputs_scroll_up_full? args
          scroll_up_full
        elsif inputs_scroll_down_full? args
          scroll_down_full
        elsif inputs_scroll_up_half? args
          scroll_up_half
        elsif inputs_scroll_down_half? args
          scroll_down_half
        elsif inputs_clear_command? args
          prompt.clear
          @command_history_index = -1
          @nonhistory_input = ''
        elsif args.inputs.keyboard.key_down.backspace
          prompt.backspace
        elsif args.inputs.keyboard.key_down.delete
          prompt.delete
        elsif args.inputs.keyboard.key_down.tab
          prompt.autocomplete
        end
  
        args.inputs.keyboard.key_down.clear
        args.inputs.keyboard.key_up.clear
        args.inputs.keyboard.key_held.clear
      end
  
      def write_primitive_and_return_offset(args, left, y, str, archived: false)
        if str.is_a?(Hash)
          padding = 10
          args.outputs.reserved << [left + 10, y + 5, str[:w], str[:h], str[:path]].sprite
          return str[:h] + padding
        else
          write_line args, left, y, str, archived: archived
          return line_height_px
        end
      end
  
      def write_line(args, left, y, str, archived: false)
        color = color_for_log_entry(str)
        color = color.mult_alpha(0.5) if archived
        str = str[4..-1] if str.start_with?('!c!')  # chop off loglevel color
        args.outputs.reserved << font_style.label(x: left.shift_right(10), y: y, text: str, color: color)
      end
  
      def should_tick?
        return false if !@toggled_at
        return false if slide_progress == 0
        return false if @disabled
        return visible?
      end
  
      def render args
        return if !@toggled_at
        return if slide_progress == 0
  
        @bottom = top - (h * slide_progress)
        args.outputs.reserved << [left, @bottom, w, h, *@background_color.mult_alpha(slide_progress)].solid
        args.outputs.reserved << [right.shift_left(110), @bottom.shift_up(630), 100, 100, @logo, 0, (80.0 * slide_progress).to_i].sprite
  
        y = @bottom + 2  # just give us a little padding at the bottom.
        prompt.render args, x: left.shift_right(10), y: y
        y += line_height_px * 1.5
        args.outputs.reserved << line(y: y, color: @text_color.mult_alpha(slide_progress))
        y += line_height_px.to_f / 2.0
  
        ((@log.size - @log_offset) - 1).downto(0) do |idx|
          offset_after_write = write_primitive_and_return_offset args, left, y, @log[idx]
          y += offset_after_write
          break if y > top
        end
  
        # past log separator
        args.outputs.reserved << line(y: y + line_height_px.half, color: @text_color.mult_alpha(0.25 * slide_progress))
  
        y += line_height_px
  
        ((@archived_log.size - @log_offset) - 1).downto(0) do |idx|
          offset_after_write = write_primitive_and_return_offset args, left, y, @archived_log[idx], archived: true
          y += offset_after_write
          break if y > top
        end
  
        render_log_offset args
  
        args.outputs.reserved << { x: 10.from_right, y: @bottom + 10,
                                   text: "Press CTRL+g or ESCAPE to clear the prompt.",
                                   vertical_alignment_enum: 0,
                                   alignment_enum: 2, r: 80, g: 80, b: 80 }.label!
      end
  
      def render_log_offset args
        return if @log_offset <= 0
        args.outputs.reserved << font_style.label(
          x: right.shift_left(5),
          y: top.shift_down(5 + line_height_px),
          text: "[#{@log_offset}/#{@log.size}]",
          color: @text_color,
          alignment_enum: 2
        )
      end
  
      def include_error_marker? text
        include_any_words?(text.gsub('OutputsDeprecated', ''), error_markers)
      end
  
      def error_markers
        ["exception:", "error:", "undefined method", "failed", "syntax", "deprecated"]
      end
  
      def include_subdued_markers? text
        (text.start_with? "* INFO: ") && (include_any_words? text, subdued_markers)
      end
  
      def include_any_words? text, words
        words.any? { |w| text.downcase.include?(w) && !text.downcase.include?(":#{w}") }
      end
  
      def subdued_markers
        ["reloaded", "exported the", "~require~"]
      end
  
      def calc args
        if visible? &&
           @show_reason == :toast &&
           @toasted_at &&
           @toasted_at.elapsed?(@toast_duration, Kernel.global_tick_count)
          hide
        end
  
        if !$gtk.paused? && visible? && (show_reason == :exception || show_reason == :exception_on_load)
          hide
        end
  
        if $gtk.files_reloaded.length > 0
          clear_toast
          @toast_ids.clear
        end
      end
  
      def tick args
        begin
          return if @disabled
          render args
          process_inputs args
          return unless should_tick?
          calc args
          prompt.tick
          menu.tick args
        rescue Exception => e
          begin
            puts "#{e}"
            puts "* FATAL: The GTK::Console console threw an unhandled exception and has been reset. You should report this exception (along with reproduction steps) to DragonRuby."
          rescue
          end
          @disabled = true
          $stdout.puts e
          $stdout.puts "* FATAL: The GTK::Console console threw an unhandled exception and has been reset. You should report this exception (along with reproduction steps) to DragonRuby."
        end
      end
  
      def set_command_with_history_silent command, histories, show_reason = nil
        set_command_extended command: command, histories: histories, show_reason: show_reason
      end
  
      def defaults_set_command_extended
        {
          command: "puts 'Hello World'",
          histories: [],
          show_reason: nil,
          force: false
        }
      end
  
      def set_command_extended opts
        opts = defaults_set_command_extended.merge opts
        @command_history.concat opts[:histories]
        @command_history << opts[:command]  if @command_history[-1] != opts[:command]
        self.current_input_str = opts[:command] if @command_set_at != Kernel.global_tick_count || opts[:force]
        @command_set_at = Kernel.global_tick_count
        @command_history_index = -1
        save_history
      end
  
      def set_command_with_history command, histories, show_reason = nil
        set_command_with_history_silent command, histories, show_reason
        show show_reason
      end
  
      # @gtk
      def set_command command, show_reason = nil
        set_command_silent command, show_reason
        show show_reason
      end
  
      def set_command_silent command, show_reason = nil
        set_command_with_history_silent command, [], show_reason
      end
  
      def set_system_command command, show_reason = nil
        if $gtk.platform == "Mac OS X"
          set_command_silent "$gtk.system \"open #{command}\""
        else
          set_command_silent "$gtk.system \"start #{command}\""
        end
      end
  
      def system_command
        if $gtk.platform == "Mac OS X"
          "open"
        else
          "start"
        end
      end
  
      private
  
      def w
        $gtk.logical_width
      end
  
      def h
        $gtk.logical_height
      end
  
      # methods top; left; right
      # Forward to grid
      %i[top left right].each do |method|
        define_method method do
          $gtk.args.grid.send(method)
        end
      end
  
      def line_height_px
        font_style.line_height_px
      end
  
      def lines_on_one_page
        (h - 4).idiv(line_height_px)
      end
  
      def line(y:, color:)
        [left, y, right, y, *color].line
      end
  
      def include_row_marker? log_entry
        log_entry[0] == "|"
      end
  
      def include_header_marker? log_entry
        return false if (log_entry.strip.include? ".rb")
        (log_entry.start_with? "* ")    ||
        (log_entry.start_with? "** ")   ||
        (log_entry.start_with? "*** ")  ||
        (log_entry.start_with? "**** ")
      end
  
      def code? log_entry
        (just_symbol? log_entry) || (codeblock_marker? log_entry)
      end
  
      def just_symbol? log_entry
        scrubbed = log_entry.gsub("*", "").strip
        (scrubbed.start_with? ":") && (!scrubbed.include? " ") && (!scrubbed.include? "=>")
      end
  
      def code_comment? log_entry
        return true  if log_entry.strip.start_with?("# ")
        return false
      end
  
      def codeblock_marker? log_entry
        return true if log_entry.strip.start_with?("#+begin_src")
        return true if log_entry.strip.start_with?("#+end_src")
        return false
      end
  
      def color_for_plain_text log_entry
        log_entry = log_entry[4..-1] if log_entry.start_with? "!c!"
  
        if code? log_entry
          @code_color
        elsif code_comment? log_entry
          @comment_color
        elsif include_row_marker? log_entry
          @text_color
        elsif include_error_marker? log_entry
          @error_color
        elsif include_subdued_markers? log_entry
          @text_color.mult_alpha(0.5)
        elsif include_header_marker? log_entry
          @header_color
        elsif log_entry.start_with?("====")
          @header_color
        else
          @text_color
        end
      end
  
      def color_for_log_entry(log_entry)
        if log_entry.start_with?('!c!')  # loglevel color specified.
          return case log_entry[3..3].to_i
                 when 0  # spam
                   @spam_color
                 when 1  # debug
                   @debug_color
                 #when 2  # info (caught by the `else` block.)
                 #  @text_color
                 when 3  # warn
                   @warn_color
                 when 4  # error
                   @error_color
                 when 5  # unfiltered
                   @unfiltered_color
                 else
                   color_for_plain_text log_entry
                 end
        end
  
        return color_for_plain_text log_entry
      end
  
      def prompt
        @prompt ||= Prompt.new(font_style: font_style, text_color: @text_color, console_text_width: console_text_width)
      end
  
      def current_input_str
        prompt.current_input_str
      end
  
      def current_input_str=(str)
        prompt.current_input_str = str
      end
  
      def clear
        @archived_log.clear
        @log.clear
        @prompt.clear
        :console_silent_eval
      end
  
      def slide_progress
        return 0 if !@toggled_at
        if visible?
          @slide_progress = @toggled_at.global_ease(@animation_duration, :flip, :quint, :flip)
        else
          @slide_progress = @toggled_at.global_ease(@animation_duration, :flip, :quint)
        end
        @slide_progress
      end
    end
  end

#+end_src

*** console_color.rb
#+begin_src ruby
  # ./dragon/console_color.rb
  # coding: utf-8
  # Copyright 2019 DragonRuby LLC
  # MIT License
  # console_color.rb has been released under MIT (*only this file*).
  
  # Contributors outside of DragonRuby who also hold Copyright:
  # - Kevin Fischer: https://github.com/kfischer-okarin
  
  module GTK
    class Console
      class Color
        def initialize(color)
          @color = color
          @color << 255 if @color.size == 3
        end
  
        def mult_alpha(alpha_modifier)
          Color.new [@color[0], @color[1], @color[2], (@color[3].to_f * alpha_modifier).to_i]
        end
  
        # Support splat operator
        def to_a
          @color
        end
  
        def to_s
          "GTK::Console::Color #{to_h}"
        end
  
        def to_h
          { r: @color[0], g: @color[1], b: @color[2], a: @color[3] }
        end
      end
    end
  end

#+end_src

*** console_font_style.rb
#+begin_src ruby
  # ./dragon/console_font_style.rb
  # coding: utf-8
  # Copyright 2019 DragonRuby LLC
  # MIT License
  # console_font_style.rb has been released under MIT (*only this file*).
  
  # Contributors outside of DragonRuby who also hold Copyright:
  # - Kevin Fischer: https://github.com/kfischer-okarin
  
  module GTK
    class Console
      class FontStyle
        attr_reader :font, :size_enum, :line_height
  
        def initialize(font:, size_enum:, line_height:)
          @font = font
          @size_enum = size_enum
          @line_height = line_height
        end
  
        def letter_size
          @letter_size ||= $gtk.calcstringbox 'W', size_enum, font
        end
  
        def line_height_px
          @line_height_px ||= letter_size.y * line_height
        end
  
        def label(x:, y:, text:, color:, alignment_enum: 0)
          {
            x: x,
            y: y.shift_up(line_height_px),  # !!! FIXME: remove .shift_up(line_height_px) when we fix coordinate origin on labels.
            text: text,
            font: font,
            size_enum: size_enum,
            alignment_enum: alignment_enum,
            **color.to_h,
          }.label!
        end
      end
    end
  end

#+end_src

*** console_menu.rb
#+begin_src ruby
  # ./dragon/console_menu.rb
  # coding: utf-8
  # Copyright 2019 DragonRuby LLC
  # MIT License
  # console_menu.rb has been released under MIT (*only this file*).
  
  module GTK
    class Console
      class Menu
        attr_accessor :buttons
  
        def initialize console
          @console = console
        end
  
        def record_clicked
          $recording.start 100
        end
  
        def replay_clicked
          $replay.start 'replay.txt'
        end
  
        def reset_clicked
          $gtk.reset
        end
  
        def scroll_up_clicked
          @console.scroll_up_half
        end
  
        def scroll_down_clicked
          @console.scroll_down_half
        end
  
        def show_menu_clicked
          @menu_shown = :visible
        end
  
        def close_clicked
          @menu_shown = :hidden
          @console.hide
        end
  
        def hide_menu_clicked
          @menu_shown = :hidden
        end
  
        def framerate_diagnostics_clicked
          @console.scroll_to_bottom
          $gtk.framerate_diagnostics
        end
  
        def itch_wizard_clicked
          @console.scroll_to_bottom
          $wizards.itch.restart
        end
  
        def docs_clicked
          @console.scroll_to_bottom
          log Kernel.docs_classes
        end
  
        def scroll_end_clicked
          @console.scroll_to_bottom
        end
  
        def custom_buttons
          []
        end
  
        def tick args
          return unless @console.visible?
  
          @menu_shown ||= :hidden
  
          if $gtk.production
            @buttons = [
              (button id: :record,      row: 0, col:   9, text: "record gameplay",       method: :record_clicked),
              (button id: :replay,      row: 0, col:  10, text: "start replay",          method: :replay_clicked),
              *custom_buttons
            ]
          elsif @menu_shown == :hidden
            @buttons = [
              (button id: :show_menu,       row: 0, col: 10, text: "show menu", method: :show_menu_clicked),
            ]
          else
            @buttons = [
              (button id: :scroll_up,   row: 0, col:  6, text: "scroll up",             method: :scroll_up_clicked),
              (button id: :scroll_down, row: 0, col:  7, text: "scroll down",           method: :scroll_down_clicked),
              (button id: :scroll_down, row: 0, col:  8, text: "scroll end",            method: :scroll_end_clicked),
              (button id: :close,       row: 0, col:  9, text: "close console",         method: :close_clicked),
              (button id: :hide,        row: 0, col: 10, text: "hide menu",             method: :hide_menu_clicked),
  
              (button id: :record,      row: 1, col:  7, text: "record gameplay",       method: :record_clicked),
              (button id: :replay,      row: 1, col:  8, text: "start replay",          method: :replay_clicked),
              (button id: :record,      row: 1, col:  9, text: "framerate diagnostics", method: :framerate_diagnostics_clicked),
              (button id: :reset,       row: 1, col: 10, text: "reset game",            method: :reset_clicked),
  
              (button id: :reset,       row: 2, col: 10, text: "docs",                  method: :docs_clicked),
              (button id: :reset,       row: 2, col:  9, text: "itch wizard",           method: :itch_wizard_clicked),
              *custom_buttons
            ]
          end
  
          # render
          args.outputs.reserved << @buttons.map { |b| b[:primitives] }
  
          # inputs
          if args.inputs.mouse.click
            clicked = @buttons.find { |b| args.inputs.mouse.inside_rect? b[:rect] }
            if clicked
              args.inputs.mouse.click = nil
              send clicked[:method]
            end
          end
        end
  
        def rect_for_layout row, col
          col_width  = 100
          row_height = 50
          col_margin = 5
          row_margin = 5
          x = (col_margin + (col * col_width)  + (col * col_margin))
          y = (row_margin + (row * row_height) + (row * row_margin) + row_height).from_top
          { x: x, y: y, w: col_width, h: row_height }
        end
  
        def button args
          id, row, col, text, method = args[:id], args[:row], args[:col], args[:text], args[:method]
  
          font_height = @console.font_style.line_height_px.half
          {
            id: id,
            rect: (rect_for_layout row, col),
            text: text,
            method: method
          }.let do |entity|
            primitives = []
            primitives << entity[:rect].solid!(a: 164)
            primitives << entity[:rect].border!(r: 255, g: 255, b: 255)
            primitives << text.wrapped_lines(5)
                              .map_with_index do |l, i|
                                [
                                  entity[:rect][:x] + entity[:rect][:w].half,
                                  entity[:rect][:y] + entity[:rect][:h].half + font_height - (i * (font_height + 2)),
                                  l, -3, 1, 255, 255, 255
                                ]
                              end.labels
  
            entity.merge(primitives: primitives)
          end
        end
  
        def serialize
          {
            not_supported: "#{self}"
          }
        end
      end
    end
  end

#+end_src

*** console_prompt.rb
#+begin_src ruby
  # ./dragon/console_prompt.rb
  # coding: utf-8
  # Copyright 2019 DragonRuby LLC
  # MIT License
  # console_prompt.rb has been released under MIT (*only this file*).
  
  # Contributors outside of DragonRuby who also hold Copyright:
  # - Kevin Fischer: https://github.com/kfischer-okarin
  
  module GTK
    class Console
      class Prompt
        # ? Can be changed, it was just taken from my editor settings :>
        WORD_LIMITER_CHARS = "`~!@#$%^&*-=+()[]{}\|;:'\",.<>/?_ \t\n\0".chars
  
        attr_accessor :current_input_str, :font_style, :console_text_width, :last_input_str, :last_input_str_changed
  
        def initialize(font_style:, text_color:, console_text_width:)
          @prompt = '-> '
          @current_input_str = ''
          @font_style = font_style
          @text_color = text_color
          @cursor_color = Color.new [187, 21, 6]
          @console_text_width = console_text_width
  
          @cursor_position = 0
          update_cursor_position_px
  
          @last_autocomplete_prefix = nil
          @next_candidate_index = 0
        end
  
        def update_cursor_position_px
          @cursor_position_px = ($gtk.calcstringbox (@prompt + @current_input_str[0...@cursor_position]), @font_style.size_enum, @font_style.font).x
        end
  
        def current_input_str=(str)
          @current_input_str = str
          @cursor_position = str.length
          update_cursor_position_px
        end
  
        def <<(str)
          @current_input_str = @current_input_str[0...@cursor_position] + str + @current_input_str[@cursor_position..-1]
          @cursor_position += str.length
          update_cursor_position_px
          @current_input_changed_at = Kernel.global_tick_count
          reset_autocomplete
        end
  
        def backspace
          return if current_input_str.length.zero? || @cursor_position.zero?
  
          @current_input_str = @current_input_str[0...(@cursor_position - 1)] + @current_input_str[@cursor_position..-1]
          @cursor_position -= 1
          update_cursor_position_px
          reset_autocomplete
        end
  
        def delete
          return if current_input_str.length.zero? || @cursor_position == current_input_str.length
  
          @cursor_position += 1
          backspace
        end
  
        def move_cursor_left
          @cursor_position -= 1 if @cursor_position > 0
          update_cursor_position_px
        end
  
        def move_cursor_left_word
          return if @cursor_position.zero?
  
          new_pos = @cursor_position - 1
          (is_word_boundary? @current_input_str[new_pos]) ?
              (new_pos -= 1 until !(is_word_boundary? @current_input_str[new_pos - 1]) || new_pos.zero?):
              (new_pos -= 1 until (is_word_boundary? @current_input_str[new_pos - 1]) || new_pos.zero?)
  
          @cursor_position = new_pos
          update_cursor_position_px
        end
  
        def move_cursor_right
          @cursor_position += 1 if @cursor_position < current_input_str.length
          update_cursor_position_px
        end
  
        def move_cursor_right_word
          return if @cursor_position.equal? str_len
  
          new_pos = @cursor_position + 1
          (is_word_boundary? @current_input_str[new_pos]) ?
              (new_pos += 1 until !(is_word_boundary? @current_input_str[new_pos]) || (new_pos.equal? str_len)):
              (new_pos += 1 until (is_word_boundary? @current_input_str[new_pos]) || (new_pos.equal? str_len))
  
          @cursor_position = new_pos
          update_cursor_position_px
        end
  
        def move_cursor_home
          @cursor_position = 0
          update_cursor_position_px
        end
  
        def move_cursor_end
          @cursor_position = str_len
          update_cursor_position_px
        end
  
        def clear
          @current_input_str = ''
          @cursor_position = 0
          update_cursor_position_px
          reset_autocomplete
        end
  
        def autocomplete
          if !@last_autocomplete_prefix
            @last_autocomplete_prefix = calc_autocomplete_prefix
  
            puts "* AUTOCOMPLETE CANDIDATES: #{current_input_str}.."
            pretty_print_strings_as_table method_candidates(@last_autocomplete_prefix)
          else
            candidates = method_candidates(@last_autocomplete_prefix)
            return if candidates.empty?
  
            candidate = candidates[@next_candidate_index]
            candidate = candidate[0..-2] + " = " if candidate.end_with? '='
            @next_candidate_index += 1
            @next_candidate_index = 0 if @next_candidate_index >= candidates.length
            self.current_input_str = display_autocomplete_candidate(candidate)
            update_cursor_position_px
          end
        rescue Exception => e
          puts "* BUG: Tab autocompletion failed. Let us know about this.\n#{e}"
        end
  
        def pretty_print_strings_as_table items
          if items.length == 0
            puts <<-S.strip
  +--------+
  | (none) |
  +--------+
  S
          else
            # figure out the largest string
            string_width = items.sort_by { |c| -c.to_s.length }.first
  
            # add spacing to each side of the string which represents the cell width
            cell_width = string_width.length + 2
  
            # add spacing to each side of the cell to represent the column width
            column_width = cell_width + 2
  
            # determine the max number of columns that can fit on the screen
            columns = @console_text_width.idiv column_width
            columns = items.length if items.length < columns
  
            # partition the original list of items into a string to be printed
            items.each_slice(columns).each_with_index do |cells, i|
              pretty_print_row_separator string_width, cell_width, column_width, columns
              pretty_print_row cells, string_width, cell_width, column_width, columns
            end
  
            pretty_print_row_separator string_width, cell_width, column_width, columns
          end
        end
  
        def pretty_print_row cells, string_width, cell_width, column_width, columns
          # if the number of cells doesn't match the number of columns, then pad the array with empty values
          cells += (columns - cells.length).map { "" }
  
          # right align each cell value
          formated_row = "|" + cells.map do |c|
            "#{" " * (string_width.length - c.length) } #{c} |"
          end.join
  
          # remove separators between empty values
          formated_row = formated_row.gsub("  |  ", "     ")
  
          puts formated_row
        end
  
        def pretty_print_row_separator string_width, cell_width, column_width, columns
          # this is a joint: +--------
          column_joint = "+#{"-" * cell_width}"
  
          # multiple joints create a row separator: +----+----+
          puts (column_joint * columns) + "+"
        end
  
        def render(args, x:, y:)
          args.outputs.reserved << font_style.label(x: x, y: y, text: "#{@prompt}#{current_input_str}", color: @text_color)
          args.outputs.reserved << (@cursor_color.to_h.merge x: x + @cursor_position_px + 0.5,
                                                             y: y + 5,
                                                             x2: x + @cursor_position_px + 0.5,
                                                             y2: y + @font_style.letter_size.y + 4)
  
          args.outputs.reserved << (@cursor_color.to_h.merge x: x + @cursor_position_px + 1,
                                                             y: y + 5,
                                                             x2: x + @cursor_position_px + 1,
                                                             y2: y + @font_style.letter_size.y + 4)
  
          # debugging rectangle for string
          # args.outputs.reserved << (@cursor_color.to_h.merge x: x,
          #                                                    y: y + 5,
          #                                                    w: @cursor_position_px,
          #                                                    h: @font_style.letter_size.y).border
        end
  
        def tick
          if (@current_input_changed_at) &&
             (@current_input_changed_at < Kernel.global_tick_count) &&
             (@last_input_str != @current_input_str)
            @last_input_str_changed = true
            @last_input_str = "#{@current_input_str}"
            @current_input_changed_at = nil
          else
            @last_input_str_changed = false
          end
        end
  
        private
  
        def last_period_index
          current_input_str.rindex('.')
        end
  
        def calc_autocomplete_prefix
          if last_period_index
            current_input_str[(last_period_index + 1)..-1]
          else
            current_input_str
          end
        end
  
        def current_object
          return Kernel unless last_period_index
  
          Kernel.eval(current_input_str[0...last_period_index])
        rescue NameError
          nil
        end
  
        def method_candidates(prefix)
          current_object.autocomplete_methods.map(&:to_s).select { |m| m.start_with? prefix }
        end
  
        def display_autocomplete_candidate(candidate)
          if last_period_index
            @current_input_str[0..last_period_index] + candidate.to_s
          else
            candidate.to_s
          end
        end
  
        def reset_autocomplete
          @last_autocomplete_prefix = nil
          @next_candidate_index = 0
        end
  
        def is_word_boundary? char
          # Alternative method
          # (WORD_LIMITER_CHARS - [char]).length != WORD_LIMITER_CHARS.length
          # Production code
          WORD_LIMITER_CHARS.include? char
        end
  
        def str_len
          @current_input_str.length
        end
      end
    end
  end

#+end_src

*** controller.rb
#+begin_src ruby
  # ./dragon/controller.rb
  # coding: utf-8
  # Copyright 2019 DragonRuby LLC
  # MIT License
  # controller.rb has been released under MIT (*only this file*).
  
  module GTK
    # @gtk
    class Controller
      attr :key_down
      attr :key_up
      attr :key_held
  
      attr :left_analog_x_raw,
           :left_analog_y_raw,
           :left_analog_x_perc,
           :left_analog_y_perc,
           :right_analog_x_raw,
           :right_analog_y_raw,
           :right_analog_x_perc,
           :right_analog_y_perc
  
      attr :connected
  
      def initialize
        @key_down = Controller::Keys.new
        @key_up   = Controller::Keys.new
        @key_held = Controller::Keys.new
        @left_analog_x_raw = 0
        @left_analog_y_raw = 0
        @left_analog_x_perc = 0
        @left_analog_y_perc = 0
        @right_analog_x_raw = 0
        @right_analog_y_raw = 0
        @right_analog_x_perc = 0
        @right_analog_y_perc = 0
        @connected = false
      end
  
      def serialize
        {
          key_down: @key_down.serialize,
          key_held: @key_held.serialize,
          key_up:   @key_up.serialize
        }
      end
  
      # Clear all current key presses.
      #
      # @return [void]
      def clear
        @key_down.clear
        @key_up.clear
        @key_held.clear
      end
  
      def up
        @key_up.up || @key_held.up
      end
  
      def down
        @key_up.down || @key_held.down
      end
  
      def left
        @key_up.left || @key_held.left
      end
  
      def right
        @key_up.right || @key_held.right
      end
  
      # Activates a key into the down position.
      #
      # @param key [Symbol] The key to press down.
      #
      # @return [void]
      def activate_down(key)
        key_down.activate(key)
        key_held.deactivate(key)
        key_up.deactivate(key)
      end
  
      # Activates a key into the held down position.
      #
      # @param key [Symbol] The key to hold down.
      #
      # @return [void]
      def activate_held(key)
        key_down.deactivate(key)
        key_held.activate(key) unless key_held.send(key)
        key_up.deactivate(key)
      end
  
  
      # Activates a key release into the up position.
      #
      # @param key [Symbol] The key release up.
      #
      # @return [void]
      def activate_up(key)
        key_down.deactivate(key)
        key_held.deactivate(key)
        key_up.activate(key)
      end
  
      include DirectionalInputHelperMethods
    end
  end

#+end_src

*** controller/config.rb
#+begin_src ruby
  # ./dragon/controller/config.rb
  # coding: utf-8
  # Copyright 2019 DragonRuby LLC
  # MIT License
  # controller/config.rb has been released under MIT (*only this file*).
  
  # !!! FIXME: add console command to forget custom binding(s)
  # !!! FIXME: add console command to forget replace existing binding(s)
  # !!! FIXME: add console command go into play_around mode to make sure controller isn't wonky.
  
  module GTK
    class Controller
      class Config
        def initialize runtime
          @runtime = runtime
          @raw_joysticks = {}   # things that aren't game controllers to try to configure.
          @target = nil
          @animation_duration = (1.5).seconds
          @toggled_at = 0
          @fading = 0
          @current_part = 0
          @part_alpha = 0
          @part_alpha_increment = 10
          @joystick_state = {}
          @playing_around = false
          @used_bindings = {}
          @bindings = []
          @parts = [
            [ 919, 282, 'A button', 'a' ],
            [ 960, 323, 'B button', 'b' ],
            [ 878, 323, 'X button', 'x' ],
            [ 919, 365, 'Y button', 'y' ],
            [ 433, 246, 'left stick left', '-leftx' ],
            [ 497, 246, 'left stick right', '+leftx' ],
            [ 466, 283, 'left stick up', '-lefty' ],
            [ 466, 218, 'left stick down', '+lefty' ],
            [ 466, 246, 'left stick button', 'leftstick' ],
            [ 741, 246, 'right stick left', '-rightx' ],
            [ 802, 246, 'right stick right', '+rightx' ],
            [ 773, 283, 'right stick up', '-righty' ],
            [ 773, 218, 'right stick down', '+righty' ],
            [ 772, 246, 'right stick button', 'rightstick' ],
            [ 263, 465, 'left shoulder button', 'leftshoulder' ],
            [ 263, 503, 'left trigger', 'lefttrigger' ],
            [ 977, 465, 'right shoulder button', 'rightshoulder' ],
            [ 977, 503, 'right trigger', 'righttrigger' ],
            [ 318, 365, 'D-pad up', 'dpup' ],
            [ 360, 322, 'D-pad right', 'dpright' ],
            [ 318, 280, 'D-pad down', 'dpdown' ],
            [ 275, 322, 'D-pad left', 'dpleft' ],
            [ 570, 402, 'select/back button', 'back'],
            [ 619, 448, 'guide/home button', 'guide' ],
            [ 669, 402, 'start button', 'start' ],
          ]
        end
  
        def rawjoystick_connected jid, joystickname, guid
          return if jid < 0
          @raw_joysticks[jid] = { name: joystickname, guid: guid }
        end
  
        def rawjoystick_disconnected jid
          return if jid < 0
          if @raw_joysticks[jid] != nil
            @raw_joysticks.delete(jid)
            @runtime.ffi_misc.close_raw_joystick(jid)
            # Fade out the config screen if we were literally configuring this controller right now.
            if !@target.nil? && @target[0] == jid
              @target[0] = nil
              @toggled_at = Kernel.global_tick_count
              @fading = -1
            end
          end
        end
  
        def build_binding_string
          bindingstr = ''
          skip = false
  
          for i in 0..@parts.length-1
            if skip ; skip = false ; next ; end
  
            binding = @bindings[i]
            next if binding.nil?
  
            part = @parts[i][3]
  
            # clean up string:
            #  if axis uses -a0 for negative and +a0 for positive, just make it "leftx:a0" instead of "-leftx:-a0,+leftx:+a0"
            #  if axis uses +a0 for negative and -a0 for positive, just make it "leftx:a0~" instead of "-leftx:+a0,+leftx:-a0"
            if part == '-leftx' || part == '-lefty' || part == '-rightx' || part == '-righty'
              nextbinding = @bindings[i+1]
              if binding.start_with?('-a') && nextbinding.start_with?('+a') && binding[2..-1] == nextbinding[2..-1]
                skip = true
                part = part[1..-1]
                binding = binding[1..-1]
              elsif binding.start_with?('+a') && nextbinding.start_with?('-a') && binding[2..-1] == nextbinding[2..-1]
                skip = true
                part = part[1..-1]
                binding = "#{binding[1..-1]}~"
              end
            end
  
            bindingstr += "#{!bindingstr.empty? ? ',' : ''}#{part}:#{binding}"
          end
  
          details = @target[1]
  
          # !!! FIXME: no String.delete in mRuby?!?! Maybe so when upgrading.
          #name = details[:name].delete(',')
          # !!! FIXME: ...no regexp either...  :/
          #name = details[:name].gsub(/,/, ' ')  # !!! FIXME: will SDL let you escape these instead?
          unescaped = details[:name]
          name = ''
          for i in 0..unescaped.length-1
            ch = unescaped[i]
            name += (ch == ',') ? ' ' : ch
          end
          return "#{details[:guid]},#{name},platform:#{@runtime.platform},#{bindingstr}"
        end
  
        def move_to_different_part part
          if !@joystick_state[:axes].nil?
            @joystick_state[:axes].each { |i| i[:farthestval] = i[:startingval] if !i.nil? }
          end
          @current_part = part
        end
  
        def previous_part
          if @current_part > 0
            # remove the binding that we previous had here so it can be reused.
            bindstr = @bindings[@current_part - 1]
            @bindings[@current_part - 1] = nil
            @used_bindings[bindstr] = nil
            move_to_different_part @current_part - 1
          end
        end
  
        def next_part
          if @current_part < (@parts.length - 1)
            move_to_different_part @current_part + 1
          else
            @playing_around = true
          end
        end
  
        def set_binding bindstr
          return false if !@used_bindings[bindstr].nil?
          @used_bindings[bindstr] = @current_part
          @bindings[@current_part] = bindstr
          return true
        end
  
        # Called when a lowlevel joystick moves an axis.
        def rawjoystick_axis jid, axis, value
          return if @target.nil? || jid != @target[0] || @fading != 0 # skip if not currently considering this joystick.
  
          @joystick_state[:axes] ||= []
          @joystick_state[:axes][axis] ||= {
            moving: false,
            startingval: 0,
            currentval: 0,
            farthestval: 0
          }
  
          # this is the logic from SDL's controllermap.c, more or less, since this is hard to get right from scratch.
          state = @joystick_state[:axes][axis]
          state[:currentval] = value
          if !state[:moving]
            state[:moving] = true
            state[:startingval] = value
            state[:farthestval] = value
          end
  
          current_distance = (value - state[:startingval]).abs
          farthest_distance = (state[:farthestval] - state[:startingval]).abs
          if current_distance > farthest_distance
            state[:farthestval] = value
            farthest_distance = (state[:farthestval] - state[:startingval]).abs
          end
  
          # If we've gone out far enough and started to come back, let's bind this axis
          if (farthest_distance >= 16000) && (current_distance <= 10000)
            next_part if set_binding("#{(state[:farthestval] < 0) ? '-' : '+'}a#{axis}")
          end
        end
  
        # Called when a lowlevel joystick moves a hat.
        def rawjoystick_hat jid, hat, value
          return if @target.nil? || jid != @target[0] || @fading != 0 # skip if not currently considering this joystick.
  
          @joystick_state[:hats] ||= []
          @joystick_state[:hats][hat] = value
  
          return if value == 0   # 0 == centered, skip it
          next_part if set_binding("h#{hat}.#{value}")
        end
  
        # Called when a lowlevel joystick moves a button.
        def rawjoystick_button jid, button, pressed
          return if @target.nil? || jid != @target[0] || @fading != 0 # skip if not currently considering this joystick.
  
          @joystick_state[:buttons] ||= []
          @joystick_state[:buttons][button] = pressed
  
          return if !pressed
          next_part if set_binding("b#{button}")
        end
  
        def calc_fading
          if @fading == 0
            return 255
          elsif @fading > 0   # fading in
            percent = @toggled_at.global_ease(@animation_duration, :flip, :quint, :flip)
            if percent >= 1.0
              percent = 1.0
              @fading = 0
            end
          else  # fading out
            percent = @toggled_at.global_ease(@animation_duration, :flip, :quint)
            if percent <= 0.0
              percent = 0.0
              @fading = 0
            end
          end
  
          return (percent * 255.0).to_i
        end
  
        def render_basics args, msg, fade=255
          joystickname = @target[1][:name]
          args.outputs.primitives << [0, 0, $gtk.logical_width, $gtk.logical_height, 255, 255, 255, fade].solid
          args.outputs.primitives << [0, 0, $gtk.logical_width, $gtk.logical_height, 'dragonruby-controller.png', 0, fade, 255, 255, 255].sprite
          args.outputs.primitives << [$gtk.logical_width / 2, 700, joystickname, 2, 1, 0, 0, 0, fade].label
          args.outputs.primitives << [$gtk.logical_height / 2, 650, msg, 0, 1, 0, 0, 0, 255].label if !msg.empty?
        end
  
        def render_part_highlight args, part, alpha=255
          partsize = 41
          args.outputs.primitives << [part[0], part[1], partsize, partsize, 255, 0, 0, alpha].border
          args.outputs.primitives << [part[0]-1, part[1]-1, partsize+2, partsize+2, 255, 0, 0, alpha].border
          args.outputs.primitives << [part[0]-2, part[1]-2, partsize+4, partsize+4, 255, 0, 0, alpha].border
        end
  
        def choose_target
          if @target.nil?
            while !@raw_joysticks.empty?
              t = @raw_joysticks.shift  # see if there's a joystick waiting on us.
              next if t[0] < 0  # just in case.
              next if t[1][:guid].nil?  # did we already handle this guid? Dump it.
              @target = t
              break
            end
            return false if @target.nil?   # nothing to configure at the moment.
            @toggled_at = Kernel.global_tick_count
            @fading = 1
            @current_part = 0
            @part_alpha = 0
            @part_alpha_increment = 10
            @joystick_state = {}
            @used_bindings = {}
            @playing_around = false
            @bindings = []
          end
          return true
        end
  
        def render_part_highlight_from_bindstr args, bindstr, alpha=255
          partidx = @used_bindings[bindstr]
          return if partidx.nil?
          render_part_highlight args, @parts[partidx], alpha
        end
  
        def play_around args
          return false if !@playing_around
  
          if args.inputs.keyboard.key_down.escape
            @current_part = 0
            @part_alpha = 0
            @part_alpha_increment = 10
            @used_bindings = {}
            @playing_around = false
            @bindings = []
          elsif args.inputs.keyboard.key_down.space
            jid = @target[0]
            bindingstr = build_binding_string
            #puts("new controller binding: '#{bindingstr}'")
            @runtime.ffi_misc.add_controller_config bindingstr
            @runtime.ffi_misc.convert_rawjoystick_to_controller jid
            @target[0] = -1  # Conversion closes the raw joystick.
  
            # Handle any other pending joysticks that have the same GUID (so if you plug in four of the same model, we're already done!)
            guid = @target[1][:guid]
            @raw_joysticks.each { |jid, details|
              if details[:guid] == guid
                @runtime.ffi_misc.convert_rawjoystick_to_controller jid
                details[:guid] = nil
              end
            }
  
            # Done with this guy.
            @playing_around = false
            @toggled_at = Kernel.global_tick_count
            @fading = -1
            return false
          end
  
          render_basics args, 'Now play around with the controller, and make sure it feels right!'
          args.outputs.primitives << [$gtk.logical_width / 2, 90, '[ESCAPE]: Reconfigure, [SPACE]: Save this configuration', 0, 1, 0, 0, 0, 255].label
  
          axes = @joystick_state[:axes]
          if !axes.nil?
            for i in 0..axes.length-1
              next if axes[i].nil?
              value = axes[i][:currentval]
              next if value.nil? || (value.abs < 16000)
              render_part_highlight_from_bindstr args, "#{value < 0 ? '-' : '+'}a#{i}"
            end
          end
  
          hats = @joystick_state[:hats]
          if !hats.nil?
            for i in 0..hats.length-1
              value = hats[i]
              next if value.nil? || (value == 0)
              render_part_highlight_from_bindstr args, "h#{i}.#{value}"
            end
          end
  
          buttons = @joystick_state[:buttons]
          if !buttons.nil?
            for i in 0..buttons.length-1
              value = buttons[i]
              next if value.nil? || !value
              render_part_highlight_from_bindstr args, "b#{i}"
            end
          end
  
          return true
        end
  
        def should_tick?
          return true if @play_around
          return true if @target
          return false
        end
  
        def tick args
          return true if play_around args
          return false if !choose_target
  
          jid = @target[0]
  
          if @fading == 0
            # Cancel config?
            if args.inputs.keyboard.key_down.escape
              # !!! FIXME: prompt to ignore this joystick forever or just this run
              @toggled_at = Kernel.global_tick_count
              @fading = -1
            end
          end
  
          if @fading == 0
            if args.inputs.keyboard.key_down.backspace
              previous_part
            elsif args.inputs.keyboard.key_down.space
              next_part
            end
          end
  
          fade = calc_fading
          if (@fading < 0) && (fade == 0)
            @runtime.ffi_misc.close_raw_joystick(jid) if jid >= 0
            @target = nil   # done with this controller
            return false
          end
  
          render_basics args, (@fading >= 0) ? "We don't recognize this controller, so tell us about it!" : '', fade
  
          return true if fade < 255  # all done for now
  
          part = @parts[@current_part]
          args.outputs.primitives << [$gtk.logical_width / 2, 575, "Please press the #{part[2]}.", 0, 1, 0, 0, 0, 255].label
          render_part_highlight args, part, @part_alpha
          args.outputs.primitives << [$gtk.logical_width / 2, 90, '[ESCAPE]: Ignore controller, [BACKSPACE]: Go back one button, [SPACE]: Skip this button', 0, 1, 0, 0, 0, 255].label
  
          @part_alpha += @part_alpha_increment
          if (@part_alpha_increment > 0) && (@part_alpha >= 255)
            @part_alpha = 255
            @part_alpha_increment = -10
          elsif (@part_alpha_increment < 0) && (@part_alpha <= 0)
            @part_alpha = 0
            @part_alpha_increment = 10
          end
  
          return true
        end
      end
    end
  end

#+end_src

*** controller/keys.rb
#+begin_src ruby
  # ./dragon/controller/keys.rb
  # coding: utf-8
  # Copyright 2019 DragonRuby LLC
  # MIT License
  # controller/keys.rb has been released under MIT (*only this file*).
  
  module GTK
    class Controller
      class Keys
        include Serialize
  
        LABELS = [
          :up, :down, :left, :right,
          :a, :b, :x, :y,
          :l1, :r1,
          :l2, :r2,
          :l3, :r3,
          :start, :select, :home,
          :directional_up, :directional_down, :directional_left, :directional_right
        ].freeze
  
        LABELS.each do |label|
          attr label
        end
  
        def back
          @select
        end
  
        def back= value
          @select = value
        end
  
        def guide
          @home
        end
  
        def guide= value
          @home = value
        end
  
        # Activate a key.
        #
        # @return [void]
        def activate key
          instance_variable_set("@#{key}", Kernel.tick_count + 1)
        end
  
        # Deactivate a key.
        #
        # @return [void]
        def deactivate key
          instance_variable_set("@#{key}", nil)
        end
  
        # Clear all key inputs.
        #
        # @return [void]
        def clear
          LABELS.each { |label| deactivate(label) }
        end
  
        def truthy_keys
          LABELS.select { |label| send(label) }
        end
      end
    end
  end

#+end_src

*** directional_input_helper_methods.rb
#+begin_src ruby
  # ./dragon/directional_input_helper_methods.rb
  # coding: utf-8
  # Copyright 2019 DragonRuby LLC
  # MIT License
  # directional_input_helper_methods.rb has been released under MIT (*only this file*).
  
  module GTK
    # This is a module that contains normalization of behavior related to `up`|`down`|`left`|`right` on keyboards and controllers.
    module DirectionalInputHelperMethods
      def self.included klass
        key_state_methods = [:key_held, :key_down]
        directional_methods = [:up, :down, :left, :right]
        method_results = (directional_methods + key_state_methods).map {|m| [m, klass.instance_methods.include?(m)] }
  
        error_message = <<-S
  * ERROR
  The GTK::DirectionalKeys module should only be included in objects that respond to the following api hierarchy:
  
  - (#{ directional_methods.join("|") })
  - key_held.(#{ directional_methods.join("|") })
  - key_down.(#{ directional_methods.join("|") })
  
  #{klass} does not respond to all of these methods (here is the diagnostics):
  #{method_results.map {|m, r| "- #{m}: #{r}"}.join("\n")}
  
  Please implement the methods that returned false inthe list above.
  S
        unless method_results.map {|m, result| result}.all?
          raise error_message
        end
      end
  
      # Returns a signal indicating left (`-1`), right (`1`), or neither ('0').
      #
      # @return [Integer]
      def left_right
        return -1 if self.left
        return  1 if self.right
        return  0
      end
  
      # Returns a signal indicating up (`1`), down (`-1`), or neither ('0').
      #
      # @return [Integer]
      def up_down
        return  1 if self.up
        return -1 if self.down
        return  0
      end
  
      # Returns a normal vector (in the form of an Array with two values). If no directionals are held/down, the function returns nil.
      #
      # The possible results are:
      #
      # - ~nil~ which denotes that no directional input exists.
      # - ~[   0,    1]~ which denotes that only up is being held/pressed.
      # - ~[   0,   -1]~ which denotes that only down is being held/pressed.
      # - ~[-0.707,  0.707]~ which denotes that right and up are being pressed/held.
      # - ~[-0.707, -0.707]~ which denotes that left and down are being pressed/held.
      #
      # @gtk
      def directional_vector
        lr, ud = [self.left_right, self.up_down]
  
        if lr == 0 && ud == 0
          return nil
        elsif lr.abs == ud.abs
          return [45.vector_x * lr.sign, 45.vector_y * ud.sign, ud.sign]
        else
          return [lr, ud]
        end
      end
  
      def directional_angle
        return nil unless directional_vector
  
        Math.atan2(up_down, left_right).to_degrees
      end
  
      def method_missing m, *args
        # combine the key with ctrl_
        if m.to_s.start_with?("ctrl_")
          other_key = m.to_s.split("_").last
          define_singleton_method(m) do
            return self.key_up.send(other_key.to_sym) && self.key_up.control
          end
  
          return send(m)
        else
        # see if the key is either held or down
          define_singleton_method(m) do
            self.key_down.send(m) || self.key_held.send(m)
          end
  
          return send(m)
        end
      end
    end
  end

#+end_src

*** easing.rb
#+begin_src ruby
  # ./dragon/easing.rb
  # coding: utf-8
  # Copyright 2019 DragonRuby LLC
  # MIT License
  # easing.rb has been released under MIT (*only this file*).
  
  module GTK
    module Easing
      def self.ease start_tick, current_tick, duration, *definitions
        ease_extended start_tick,
                      current_tick,
                      start_tick + duration,
                      initial_value(*definitions),
                      final_value(*definitions),
                      *definitions
      end
  
      def self.ease_extended start_tick, current_tick, end_tick, default_before, default_after, *definitions
        definitions.flatten!
        definitions = [:identity] if definitions.length == 0
        duration = end_tick - start_tick
        elapsed  = current_tick - start_tick
        y = elapsed.percentage_of(duration).cap_min_max(0, 1)
  
        definitions.map do |definition|
          y = Easing.exec_definition(definition, start_tick, duration, y)
        end
  
        y
      end
  
      def self.ease_spline start_tick, current_tick, duration, spline
        ease_spline_extended start_tick, current_tick, start_tick + duration, spline
      end
  
      def self.ease_spline_extended start_tick, current_tick, end_tick, spline
        return spline[-1][-1] if current_tick >= end_tick
        duration = end_tick - start_tick
        t = (current_tick - start_tick).fdiv duration
        time_allocation_per_curve = 1.fdiv(spline.length)
        curve_index, curve_t = t.fdiv(time_allocation_per_curve).let do |spline_t|
          [spline_t.to_i, spline_t - spline_t.to_i]
        end
        Geometry.cubic_bezier curve_t, *spline[curve_index]
      end
  
      def self.initial_value *definitions
        definitions.flatten!
        return Easing.exec_definition (definitions.at(-1) || :identity), 0, 10, 0
      end
  
      def self.final_value *definitions
        definitions.flatten!
        return Easing.exec_definition (definitions.at(-1) || :identity), 0, 10, 1.0
      end
  
      def self.exec_definition definition, start_tick, duration, x
        if definition.is_a? Symbol
          return Easing.send(definition, x).cap_min_max(0, 1)
        elsif definition.is_a? Proc
          return definition.call(x, start_tick, duration).cap_min_max(0, 1)
        end
  
        raise <<-S
  * ERROR:
  I don't know how to execute easing function with definition #{definition}.
  
  S
      end
  
      def self.identity x
        x
      end
  
      def self.flip x
        1 - x
      end
  
      def self.quad x
        x * x
      end
  
      def self.cube x
        x * x * x
      end
  
      def self.quart x
        x * x * x * x * x
      end
  
      def self.quint x
        x * x * x * x * x * x
      end
    end
  end
  
  Easing = GTK::Easing

#+end_src

*** entity.rb
#+begin_src ruby
  # ./dragon/entity.rb
  # coding: utf-8
  # Copyright 2019 DragonRuby LLC
  # MIT License
  # entity.rb has been released under MIT (*only this file*).
  
  module GTK
    class Entity
      def self.id!
        @id ||= 0
        @id += 1
        @id
      end
  
      def self.__reset_id__!
        @id = 0
      end
  
      def self.strict_entities
        @strict_entities ||= {}
        @strict_entities
      end
  
      def self.parse_serialization_data data
        r = Entity.parse_serialization_data data
        return r if r.is_a? OpenEntity
        return r if r.is_a? StrictEntity
        raise <<-S
  * ERROR:
  The save data looks to be corrupt.
  
  S
      end
  
      def self.parse_serialization_data value
        if value.is_a?(Hash) && value[:entity_id] && value[:entity_strict]
          o = new_entity_strict value[:entity_name], value
          o.load_entity_data! value
          return o
        elsif value.is_a?(Hash) && value[:entity_id]
          o = OpenEntity.new
          o.load_entity_data! value
          return o
        elsif value.is_a? Array
          return value.map { |entry| Entity.parse_serialization_data entry }
        else
          return value
        end
      end
  
      def self.new_entity entity_type, init_hash = nil, block = nil
        n = OpenEntity.new(entity_type)
        n.entity_type = entity_type
        n.created_at = Kernel.tick_count
        n.global_created_at = Kernel.global_tick_count
  
        if init_hash
          init_hash.each do |k, v|
            n.as_hash[k] = v
          end
        end
  
        block.call(n) if block
  
        n
      end
  
      def self.new_entity_strict entity_type, init_hash = nil, block = nil
        if !Entity.strict_entities[entity_type]
          init_hash ||= { }
  
          n = new_entity entity_type, init_hash, block
          klass = Class.new(StrictEntity)
  
          klass.class_eval do
            init_hash.each do |k, v|
              attr_accessor k
            end
  
            n.as_hash.each do |k, v|
              attr_accessor k if !init_hash[k]
            end
          end
  
          Entity.strict_entities[entity_type] = klass
        end
  
        klass = Entity.strict_entities[entity_type]
        (klass.new entity_type, init_hash, block)
      end
    end
  end

#+end_src

*** geometry.rb
#+begin_src ruby
  # ./dragon/geometry.rb
  # coding: utf-8
  # Copyright 2019 DragonRuby LLC
  # MIT License
  # geometry.rb has been released under MIT (*only this file*).
  
  module GTK
    module Geometry
      def self.rotate_point point, angle, around = nil
        s = Math.sin angle.to_radians
        c = Math.cos angle.to_radians
        px = point.x
        py = point.y
        cx = 0
        cy = 0
        if around
          cx = around.x
          cy = around.y
        end
  
        point.merge(x: ((px - cx) * c - (py - cy) * s) + cx,
                    y: ((px - cx) * s + (py - cy) * c) + cy)
      end
  
      # Returns f(t) for a cubic Bezier curve.
      def self.cubic_bezier t, a, b, c, d
        s  = 1 - t
        s0 = 1
        s1 = s
        s2 = s * s
        s3 = s * s * s
  
        t0 = 1
        t1 = t
        t2 = t * t
        t3 = t * t * t
  
        1 * s3 * t0 * a +
        3 * s2 * t1 * b +
        3 * s1 * t2 * c +
        1 * s0 * t3 * d
      end
  
      # Returns true if a primitive's rectangle is entirely inside another primitive's rectangle.
      # @gtk
      def inside_rect? outer, tolerance = 0.0
        Geometry.inside_rect? self, outer, tolerance
      end
  
      # Returns true if a primitive's rectangle overlaps another primitive's rectangle.
      # @gtk
      def intersect_rect? other, tolerance = 0.1
        Geometry.intersect_rect? self, other, tolerance
      end
  
      def intersects_rect? *args
        Geometry.intersects_rect?(*args)
      end
  
      def scale_rect_extended percentage_x: percentage_x,
                              percentage_y: percentage_y,
                              anchor_x: anchor_x,
                              anchor_y: anchor_y
  
        Geometry.scale_rect_extended self,
                                     percentage_x: percentage_x,
                                     percentage_y: percentage_y,
                                     anchor_x: anchor_x,
                                     anchor_y: anchor_y
      end
  
      # Scales a primitive rect by a percentage.
      # @gtk
      def scale_rect percentage, *anchors
        Geometry.scale_rect self, percentage, *anchors
      end
  
      # Returns the angle from one primitive to another primitive.
      # @gtk
      def angle_to other_point
        Geometry.angle_to self, other_point
      end
  
      # Returns the angle to one primitive from another primitive.
      # @gtk
      def angle_from other_point
        Geometry.angle_from self, other_point
      end
  
      # Returns true if a primitive is within a circle specified by the circle's center and radius.
      # @gtk
      def point_inside_circle? circle_center_point, radius
        Geometry.point_inside_circle? self, circle_center_point, radius
      end
  
      def self.center_inside_rect rect, other_rect
        offset_x = (other_rect.w - rect.w).half
        offset_y = (other_rect.h - rect.h).half
        new_rect = rect.shift_rect(0, 0)
        new_rect.x = other_rect.x + offset_x
        new_rect.y = other_rect.y + offset_y
        new_rect
      rescue Exception => e
        raise e, <<-S
  * ERROR:
  center_inside_rect for self #{self} and other_rect #{other_rect}.\n#{e}.
  S
      end
  
      def center_inside_rect other_rect
        Geometry.center_inside_rect self, other_rect
      end
  
      def self.center_inside_rect_x rect, other_rect
        offset_x   = (other_rect.w - rect.w).half
        new_rect   = rect.shift_rect(0, 0)
        new_rect.x = other_rect.x + offset_x
        new_rect.y = other_rect.y
        new_rect
      rescue Exception => e
        raise e, <<-S
  * ERROR:
  center_inside_rect_x for self #{self} and other_rect #{other_rect}.\n#{e}.
  S
      end
  
      def center_inside_rect_x other_rect
        Geometry.center_inside_rect_x self, other_rect
      end
  
      def self.center_inside_rect_y rect, other_rect
        offset_y = (other_rect.h - rect.h).half
        new_rect = rect.shift_rect(0, 0)
        new_rect.x = other_rect.x
        new_rect.y = other_rect.y + offset_y
        new_rect
      rescue Exception => e
        raise e, <<-S
  * ERROR:
  center_inside_rect_y for self #{self} and other_rect #{other_rect}.\n#{e}.
  S
      end
  
      def center_inside_rect_y other_rect
        Geometry.center_inside_rect_y self, other_rect
      end
  
  
      # Returns a primitive that is anchored/repositioned based off its rectangle.
      # @gtk
      def anchor_rect anchor_x, anchor_y
        current_w = self.w
        current_h = self.h
        delta_x = -1 * (anchor_x * current_w)
        delta_y = -1 * (anchor_y * current_h)
        self.shift_rect(delta_x, delta_y)
      end
  
      def angle_given_point other_point
        raise ":angle_given_point has been deprecated use :angle_from instead."
      end
  
      # @gtk
      def self.shift_line line, x, y
        if line.is_a?(Array) || line.is_a?(Hash)
          new_line = line.dup
          new_line.x  += x
          new_line.x2 += x
          new_line.y  += y
          new_line.y2 += y
          new_line
        else
          raise "shift_line for #{line} is not supported."
        end
      end
  
      def self.intersects_rect? *args
        raise <<-S
  intersects_rect? (with an \"s\") has been deprecated.
  Use intersect_rect? instead (remove the \"s\").
  
  * NOTE:
  Ruby's naming convention is to *never* include the \"s\" for
  interrogative method names (methods that end with a ?). It
  doesn't sound grammatically correct, but that has been the
  rule for a long time (and why intersects_rect? has been deprecated).
  
  S
      end
  
      # @gtk
      def self.line_y_intercept line, replace_infinity: nil
        line.y - line_slope(line, replace_infinity: replace_infinity) * line.x
      rescue Exception => e
  raise <<-S
  * ERROR: ~Geometry::line_y_intercept~
  The following exception was thrown for line: #{line}
  #{e}
  
  Consider passing in ~replace_infinity: VALUE~ to handle for vertical lines.
  S
      end
  
      # @gtk
      def self.angle_between_lines line_one, line_two, replace_infinity: nil
        m_line_one = line_slope line_one, replace_infinity: replace_infinity
        m_line_two = line_slope line_two, replace_infinity: replace_infinity
        Math.atan((m_line_one - m_line_two) / (1 + m_line_two * m_line_one)).to_degrees
      end
  
      # @gtk
      def self.line_slope line, replace_infinity: nil
        return replace_infinity if line.x2 == line.x
        (line.y2 - line.y).fdiv(line.x2 - line.x)
                          .replace_infinity(replace_infinity)
      end
  
      def self.line_rise_run line
        rise = (line.y2 - line.y).to_f
        run  = (line.x2 - line.x).to_f
        if rise.abs > run.abs && rise != 0
          rise = rise.fdiv rise.abs
          run = run.fdiv rise.abs
        elsif run.abs > rise.abs && run != 0
          rise = rise.fdiv run.abs
          run = run.fdiv run.abs
        else
          rise = rise / rise.abs if rise != 0
          run = run / run.abs if run != 0
        end
        return { x: run , y: rise }
      end
  
      # @gtk
      def self.ray_test point, line
        slope = (line.y2 - line.y).fdiv(line.x2 - line.x)
  
        if line.x > line.x2
          point_two, point_one = [point_one, point_two]
        end
  
        r = ((line.x2 - line.x) * (point.y - line.y) -
             (point.x -  line.x) * (line.y2 - line.y))
  
        if r == 0
          return :on
        elsif r < 0
          return :right if slope >= 0
          return :left
        elsif r > 0
          return :left if slope >= 0
          return :right
        end
      end
  
      # @gtk
      def self.line_rect line
        if line.x > line.x2
          x  = line.x2
          y  = line.y2
          x2 = line.x
          y2 = line.y
        else
          x  = line.x
          y  = line.y
          x2 = line.x2
          y2 = line.y2
        end
  
        w = x2 - x
        h = y2 - y
  
        { x: x, y: y, w: w, h: h }
      end
  
      # @gtk
      def self.line_intersect line_one, line_two, replace_infinity: nil
        m1 = line_slope(line_one, replace_infinity: replace_infinity)
        m2 = line_slope(line_two, replace_infinity: replace_infinity)
        b1 = line_y_intercept(line_one, replace_infinity: replace_infinity)
        b2 = line_y_intercept(line_two, replace_infinity: replace_infinity)
        x = (b1 - b2) / (m2 - m1)
        y = (-b2.fdiv(m2) + b1.fdiv(m1)).fdiv(1.fdiv(m1) - 1.fdiv(m2))
        [x, y]
      rescue Exception => e
  raise <<-S
  * ERROR: ~Geometry::line_intersect~
  The following exception was thrown for line_one: #{line_one}, line_two: #{line_two}
  #{e}
  
  Consider passing in ~replace_infinity: VALUE~ to handle for vertical lines.
  S
      end
  
      def self.contract_intersect_rect?
        [:left, :right, :top, :bottom]
      end
  
      # @gtk
      def self.intersect_rect? rect_one, rect_two, tolerance = 0.1
        return false if ((rect_one.x + rect_one.w) - tolerance) < (rect_two.x + tolerance)
        return false if (rect_one.x + tolerance) > ((rect_two.x + rect_two.w) - tolerance)
        return false if ((rect_one.y + rect_one.h) - tolerance) < (rect_two.y + tolerance)
        return false if (rect_one.y + tolerance) > ((rect_two.y + rect_two.h) - tolerance)
        return true
      rescue Exception => e
        context_help_rect_one = (rect_one.__help_contract_implementation contract_intersect_rect?)[:not_implemented_methods]
        context_help_rect_two = (rect_two.__help_contract_implementation contract_intersect_rect?)[:not_implemented_methods]
        context_help = ""
        if context_help_rect_one && context_help_rect_one.length > 0
          context_help += <<-S
  rect_one needs to implement the following methods: #{context_help_rect_one}
  
  You may want to try include the ~AttrRect~ module which will give you these methods.
  S
        end
  
        if context_help_rect_two && context_help_rect_two.length > 0
          context_help += <<-S
  * FAILURE REASON:
  rect_two needs to implement the following methods: #{context_help_rect_two}
  NOTE: You may want to try include the ~GTK::Geometry~ module which will give you these methods.
  S
        end
  
        raise e, <<-S
  * ERROR:
  :intersect_rect? failed for
  - rect_one: #{rect_one}
  - rect_two: #{rect_two}
  #{context_help}
  \n#{e}
  S
      end
  
      # @gtk
      def self.to_square size, x, y, anchor_x = 0.5, anchor_y = nil
        anchor_y ||= anchor_x
        x = x.shift_left(size * anchor_x)
        y = y.shift_down(size * anchor_y)
        [x, y, size, size]
      rescue Exception => e
        raise e, ":to_square failed for size: #{size} x: #{x} y: #{y} anchor_x: #{anchor_x} anchor_y: #{anchor_y}.\n#{e}"
      end
  
      # @gtk
      def self.distance point_one, point_two
        Math.sqrt((point_two.x - point_one.x)**2 + (point_two.y - point_one.y)**2)
      rescue Exception => e
        raise e, ":distance failed for point_one: #{point_one} point_two #{point_two}.\n#{e}"
      end
  
      # @gtk
      def self.angle_from start_point, end_point
        d_y = end_point.y - start_point.y
        d_x = end_point.x - start_point.x
        Math::PI.+(Math.atan2(d_y, d_x)).to_degrees
      rescue Exception => e
        raise e, ":angle_from failed for start_point: #{start_point} end_point: #{end_point}.\n#{e}"
      end
  
      # @gtk
      def self.angle_to start_point, end_point
        angle_from end_point, start_point
      rescue Exception => e
        raise e, ":angle_to failed for start_point: #{start_point} end_point: #{end_point}.\n#{e}"
      end
  
      # @gtk
      def self.point_inside_circle? point, circle_center_point, radius
        (point.x - circle_center_point.x) ** 2 + (point.y - circle_center_point.y) ** 2 < radius ** 2
      rescue Exception => e
        raise e, ":point_inside_circle? failed for point: #{point} circle_center_point: #{circle_center_point} radius: #{radius}.\n#{e}"
      end
  
      # @gtk
      def self.inside_rect? inner_rect, outer_rect, tolerance = 0.0
        return nil if !inner_rect
        return nil if !outer_rect
  
        inner_rect.x     + tolerance >= outer_rect.x     - tolerance &&
        (inner_rect.x + inner_rect.w) - tolerance <= (outer_rect.x + outer_rect.w) + tolerance &&
        inner_rect.y     + tolerance >= outer_rect.y     - tolerance &&
        (inner_rect.y + inner_rect.h) - tolerance <= (outer_rect.y + outer_rect.h) + tolerance
      rescue Exception => e
        raise e, ":inside_rect? failed for inner_rect: #{inner_rect} outer_rect: #{outer_rect}.\n#{e}"
      end
  
      # @gtk
      def self.scale_rect_extended rect,
                                   percentage_x: percentage_x,
                                   percentage_y: percentage_y,
                                   anchor_x: anchor_x,
                                   anchor_y: anchor_y
        anchor_x ||= 0.0
        anchor_y ||= 0.0
        percentage_x ||= 1.0
        percentage_y ||= 1.0
        new_w = rect.w * percentage_x
        new_h = rect.h * percentage_y
        new_x = rect.x + (rect.w - new_w) * anchor_x
        new_y = rect.y + (rect.h - new_h) * anchor_y
        if rect.is_a? Array
          return [
            new_x,
            new_y,
            new_w,
            new_h,
            *rect[4..-1]
          ]
        elsif rect.is_a? Hash
          return rect.merge(x: new_x, y: new_y, w: new_w, h: new_h)
        else
          rect.x = new_x
          rect.y = new_y
          rect.w = new_w
          rect.h = new_h
          return rect
        end
      rescue Exception => e
        raise e, ":scale_rect_extended failed for rect: #{rect} percentage_x: #{percentage_x} percentage_y: #{percentage_y} anchors_x: #{anchor_x} anchor_y: #{anchor_y}.\n#{e}"
      end
  
      # @gtk
      def self.scale_rect rect, percentage, *anchors
        anchor_x, anchor_y = *anchors.flatten
        anchor_x ||= 0
        anchor_y ||= anchor_x
        Geometry.scale_rect_extended rect,
                                     percentage_x: percentage,
                                     percentage_y: percentage,
                                     anchor_x: anchor_x,
                                     anchor_y: anchor_y
      rescue Exception => e
        raise e, ":scale_rect failed for rect: #{rect} percentage: #{percentage} anchors [#{anchor_x} (x), #{anchor_y} (y)].\n#{e}"
      end
  
      def self.rect_to_line rect
        l = rect.to_hash.line
        l.merge(x2: l.x + l.w - 1,
                y2: l.y + l.h)
      end
  
      def self.rect_center_point rect
        { x: rect.x + rect.w.half, y: rect.y + rect.h.half }
      end
  
      def rect_center_point
        Geometry.rect_center_point self
      end
    end # module Geometry
  end # module GTK

#+end_src

*** grid.rb
#+begin_src ruby
  # ./dragon/grid.rb
  # coding: utf-8
  # Copyright 2019 DragonRuby LLC
  # MIT License
  # grid.rb has been released under MIT (*only this file*).
  
  module GTK
    class Grid
      include Serialize
      SCREEN_Y_DIRECTION = -1.0
  
      # The coordinate system currently in use.
      #
      # @return [Symbol] `:bottom_left` or `:center`
      attr_accessor :name
  
      # Returns the "x" coordinate indicating the bottom of the screen.
      #
      # @return [Float]
      attr_accessor :bottom
  
      # Returns the "x" coordinate indicating the top of the screen.
      #
      # @return [Float]
      attr_accessor :top
  
      # Returns the "y" coordinate indicating the left of the screen.
      #
      # @return [Float]
      attr_accessor :left
  
      # Returns the "y" coordinate indicating the right of the screen.
      #
      # @return [Float]
      attr_accessor :right
  
      # Returns the "x" coordinate indicating the center of the screen.
      #
      # @return [Float]
      attr_accessor :center_x
  
      # Returns the "y" coordinate indicating the center of the screen.
      #
      # @return [Float]
      attr_accessor :center_y
  
      # Returns the bottom left and top right coordinates in a single list.
      #
      # @return [[Float, Float, Float, Float]]
      attr_accessor :rect
  
      # Returns the "x" coordinate of the origin.
      #
      # @return [Float]
      attr_accessor :origin_x
  
      # Returns the "y" coordinate of the origin.
      #
      # @return [Float]
      attr_accessor :origin_y
  
      attr_accessor :left_margin, :bottom_margin
  
      def initialize runtime
        @runtime = runtime
        @ffi_draw = runtime.ffi_draw
        origin_bottom_left!
      end
  
      # Returns `x` plus the origin "x".
      #
      # @return [Float]
      def transform_x x
        @origin_x + x
      end
  
      # Returns `x` minus the origin "x".
      #
      # @return [Float]
      def untransform_x x
        x - @origin_x
      end
  
      # Returns `y` plus the origin "y".
      #
      # @return [Float]
      def transform_y y
        @origin_y + y * SCREEN_Y_DIRECTION
      end
  
      # Returns `y` minus the origin "y".
      #
      # @return [Float]
      def untransform_y y
        @origin_y + y * SCREEN_Y_DIRECTION
      end
  
      def ffi_draw
        @ffi_draw
      end
  
      def ffi_draw= value
        @ffi_draw = value
      end
  
      # Sets the rendering coordinate system to have its origin in the bottom left.
      #
      # @return [void]
      # @gtk
      def origin_bottom_left!
        return if @name == :bottom_left
        @name = :bottom_left
        @origin_x = 0.0
        @origin_y = @runtime.logical_height
        @left   = 0.0
        @right  = @runtime.logical_width
        @top    = @runtime.logical_height
        @bottom = 0.0
        @left_margin = 0.0
        @bottom_margin = 0.0
        @center_x = @runtime.logical_width.half
        @center_y = @runtime.logical_height.half
        @rect   = [@left, @bottom, @runtime.logical_width, @runtime.logical_height].rect
        @center = [@center_x, @center_y].point
        @ffi_draw.set_grid @origin_x, @origin_y, SCREEN_Y_DIRECTION
      end
  
      # Sets the rendering coordinate system to have its origin in the center.
      #
      # @return [void]
      # @gtk
      def origin_center!
        return if @name == :center
        @name = :center
        @origin_x = @runtime.logical_width.half
        @origin_y = @runtime.logical_height.half
        @left   =  -@runtime.logical_width.half
        @right  =   @runtime.logical_width.half
        @top    =   @runtime.logical_height.half
        @bottom =  -@runtime.logical_height.half
        @center_x = 0.0
        @center_y = 0.0
        @rect   = [@left, @bottom, @runtime.logical_width, @runtime.logical_height].rect
        @center = [@center_x, @center_y].point
        @ffi_draw.set_grid @origin_x, @origin_y, SCREEN_Y_DIRECTION
      end
  
      # The logical width used for rendering.
      #
      # @return [Float]
      def w
        @runtime.logical_width
      end
  
      # Half the logical width used for rendering.
      #
      # @return [Float]
      def w_half
        w.half
      end
  
      # The logical height used for rendering.
      #
      # @return [Float]
      def h
        @runtime.logical_height
      end
  
      # Half the logical height used for rendering.
      #
      # @return [Float]
      def h_half
        h.half
      end
  
      # Returns the coordinates indicating the center of the screen.
      #
      # @return [[Float, Float]]
      def center
        @center
      end
  
      # Returns the coordinates indicating the bottom right of the screen.
      #
      # @return [[Float, Float]]
      def bottom_right
        [@right, @bottom].point
      end
  
      def x
        0
      end
  
      def y
        0
      end
    end
  end

#+end_src

*** inputs.rb
#+begin_src ruby
  # ./dragon/inputs.rb
  # coding: utf-8
  # Copyright 2019 DragonRuby LLC
  # MIT License
  # inputs.rb has been released under MIT (*only this file*).
  
  module GTK
    # Represents all the keys available on the keyboard.
    # @gtk
    class KeyboardKeys
      include Serialize
  
      # @gtk
      attr_accessor :exclamation_point,
                    :zero, :one, :two, :three, :four,
                    :five, :six, :seven, :eight, :nine,
                    :backspace, :delete, :escape, :enter, :tab,
                    :open_round_brace, :close_round_brace,
                    :open_curly_brace, :close_curly_brace,
                    :open_square_brace, :close_square_brace,
                    :colon, :semicolon, :equal_sign,
                    :hyphen, :space, :dollar_sign,
                    :double_quotation_mark,
                    :single_quotation_mark,
                    :backtick,
                    :tilde, :period, :comma, :pipe,
                    :underscore,
                    :a, :b, :c, :d, :e, :f, :g, :h,
                    :i, :j, :k, :l, :m, :n, :o, :p,
                    :q, :r, :s, :t, :u, :v, :w, :x,
                    :y, :z,
                    :shift, :control, :alt, :meta,
                    :shift_left, :shift_right,
                    :control_left, :control_right,
                    :alt_left, :alt_right,
                    :meta_left, :meta_right,
                    :home, :end,
                    :left, :right, :up, :down, :pageup, :pagedown,
                    :char, :plus, :at, :forward_slash, :back_slash, :asterisk,
                    :less_than, :greater_than, :carat, :ampersand, :superscript_two,
                    :circumflex,
                    :question_mark, :section_sign, :ordinal_indicator,
                    :raw_key
  
      def self.sdl_to_key raw_key, modifier
        return nil unless (raw_key >= 0 && raw_key <= 255) ||
                          raw_key == 1073741903 ||
                          raw_key == 1073741904 ||
                          raw_key == 1073741905 ||
                          raw_key == 1073741906 ||
                          raw_key == 1073741899 ||
                          raw_key == 1073741902 ||
                          raw_key == 1073741898 ||
                          raw_key == 1073741901 ||
                          (raw_key >= 1073742048 && raw_key <= 1073742055) # Modifier Keys
  
        char = KeyboardKeys.char_with_shift raw_key, modifier
        names = KeyboardKeys.char_to_method char, raw_key
        names << :alt if (modifier & (256|512)) != 0    # alt key
        names << :meta if (modifier & (1024|2048)) != 0 # meta key (command/apple/windows key)
        names << :control if (modifier & (64|128)) != 0 # ctrl key
        names << :shift if (modifier & (1|2)) != 0      # shift key
        names
      end
  
      def self.utf_8_char raw_key
        return "²" if raw_key == 178
        return "§" if raw_key == 167
        return "º" if raw_key == 186
        return raw_key.chr
      end
  
      def self.char_with_shift raw_key, modifier
        return nil unless raw_key >= 0 && raw_key <= 255
        if modifier != 1 && modifier != 2 && modifier != 3
          return utf_8_char raw_key
        else
          @shift_keys ||= {
            '`' => '~', '-' => '_', "'" => '"', "1" => '!',
            "2" => '@', "3" => '#', "4" => '$', "5" => '%',
            "6" => '^', "7" => '&', "8" => '*', "9" => '(',
            "0" => ')', ";" => ":", "=" => "+", "[" => "{",
            "]" => "}", '\\'=> "|", '/' => "?", '.' => ">",
            ',' => "<", 'a' => 'A', 'b' => 'B', 'c' => 'C',
            'd' => 'D', 'e' => 'E', 'f' => 'F', 'g' => 'G',
            'h' => 'H', 'i' => 'I', 'j' => 'J', 'k' => 'K',
            'l' => 'L', 'm' => 'M', 'n' => 'N', 'o' => 'O',
            'p' => 'P', 'q' => 'Q', 'r' => 'R', 's' => 'S',
            't' => 'T', 'u' => 'U', 'v' => 'V', 'w' => 'W',
            'x' => 'X', 'y' => 'Y', 'z' => 'Z'
          }
  
          @shift_keys[raw_key.chr.to_s] || raw_key.chr.to_s
        end
      end
  
      def self.char_to_method_hash
        @char_to_method ||= {
          'A'  => [:a],
          'B'  => [:b],
          'C'  => [:c],
          'D'  => [:d],
          'E'  => [:e],
          'F'  => [:f],
          'G'  => [:g],
          'H'  => [:h],
          'I'  => [:i],
          'J'  => [:j],
          'K'  => [:k],
          'L'  => [:l],
          'M'  => [:m],
          'N'  => [:n],
          'O'  => [:o],
          'P'  => [:p],
          'Q'  => [:q],
          'R'  => [:r],
          'S'  => [:s],
          'T'  => [:t],
          'U'  => [:u],
          'V'  => [:v],
          'W'  => [:w],
          'X'  => [:x],
          'Y'  => [:y],
          'Z'  => [:z],
          "!"  => [:exclamation_point],
          "0"  => [:zero],
          "1"  => [:one],
          "2"  => [:two],
          "3"  => [:three],
          "4"  => [:four],
          "5"  => [:five],
          "6"  => [:six],
          "7"  => [:seven],
          "8"  => [:eight],
          "9"  => [:nine],
          "\b" => [:backspace],
          "\e" => [:escape],
          "\r" => [:enter],
          "\t" => [:tab],
          "("  => [:open_round_brace],
          ")"  => [:close_round_brace],
          "{"  => [:open_curly_brace],
          "}"  => [:close_curly_brace],
          "["  => [:open_square_brace],
          "]"  => [:close_square_brace],
          ":"  => [:colon],
          ";"  => [:semicolon],
          "="  => [:equal_sign],
          "-"  => [:hyphen],
          " "  => [:space],
          "$"  => [:dollar_sign],
          "\"" => [:double_quotation_mark],
          "'"  => [:single_quotation_mark],
          "`"  => [:backtick],
          "~"  => [:tilde],
          "."  => [:period],
          ","  => [:comma],
          "|"  => [:pipe],
          "_"  => [:underscore],
          "#"  => [:hash],
          "+"  => [:plus],
          "@"  => [:at],
          "/"  => [:forward_slash],
          "\\" => [:back_slash],
          "*"  => [:asterisk],
          "<"  => [:less_than],
          ">"  => [:greater_than],
          "^"  => [:circumflex],
          "&"  => [:ampersand],
          "²"  => [:superscript_two],
          "§"  => [:section_sign],
          "?"  => [:question_mark],
          '%'  => [:percent_sign],
          "º"  => [:ordinal_indicator],
          1073741898 => [:home],
          1073741901 => [:end],
          1073741903 => [:right],
          1073741904 => [:left],
          1073741905 => [:down],
          1073741906 => [:up],
          1073741899 => [:pageup],
          1073741902 => [:pagedown],
          127 => [:delete],
          1073742049 => [:shift_left, :shift],
          1073742053 => [:shift_right, :shift],
          1073742048 => [:control_left, :control],
          1073742052 => [:control_right, :control],
          1073742050 => [:alt_left, :alt],
          1073742054 => [:alt_right, :alt],
          1073742051 => [:meta_left, :meta],
          1073742055 => [:meta_right, :meta]
        }
      end
  
      def self.method_to_key_hash
        return @method_to_key_hash if @method_to_key_hash
        @method_to_key_hash = {}
        string_representation_overrides ||= {
          backspace: '\b'
        }
        char_to_method_hash.each do |k, v|
          v.each do |vi|
            t = { char_or_raw_key: k }
  
            if k.is_a? Numeric
              t[:raw_key] = k
              t[:string_representation] = "raw_key == #{k}"
            else
              t[:char] = k
              t[:string_representation] = "\"#{k.strip}\""
            end
  
            @method_to_key_hash[vi] = t
          end
        end
        @method_to_key_hash
      end
  
      def self.char_to_method char, int = nil
        methods = char_to_method_hash[char] || char_to_method_hash[int]
        methods ? methods.dup : [char.to_sym || int]
      end
  
      def clear
        set truthy_keys, false
        @scrubbed_ivars = nil
      end
  
      # @gtk
      def left_right
        return -1 if self.left
        return  1 if self.right
        return  0
      end
  
      # @gtk
      def up_down
        return  1 if self.up
        return -1 if self.down
        return  0
      end
  
      # @gtk
      def truthy_keys
        get(all).find_all { |_, v| v }
                .map { |k, _| k.to_sym }
      end
  
      # @gtk
      def all? keys
        values = get(keys.map { |k| k.without_ending_bang })
        all_true = values.all? do |k, v|
          v
        end
  
        if all_true
          keys.each do |k|
            clear_key k if k.end_with_bang?
          end
        end
  
        all_true
      end
  
      # @gtk
      def any? keys
        values = get(keys.map { |k| k.without_ending_bang })
        any_true = values.any? do |k, v|
          v
        end
  
        if any_true
          keys.each do |k|
            clear_key k if k.end_with_bang?
          end
        end
  
        any_true
      end
  
      # @gtk
      def clear_key key
        @scrubbed_ivars = nil
        self.instance_variable_set("@#{key.without_ending_bang}", false)
      end
  
      # @gtk
      def all
        @scrubbed_ivars ||= self.instance_variables
                                .reject { |i| i == :@all || i == :@scrubbed_ivars }
                                .map { |i| i.to_s.gsub("@", "") }
  
        get(@scrubbed_ivars).map { |k, _| k }
      end
  
      # @gtk
      def get collection
        return [] if collection.length == 0
        collection.map do |m|
          if m.end_with_bang?
            clear_after_return = true
          end
  
          value = self.instance_variable_get("@#{m.without_ending_bang}".to_sym)
          clear_key m if clear_after_return
          [m.without_ending_bang, value]
        end
      end
  
      # @gtk
      def set collection, value = true
        return if collection.length == 0
        @scrubbed_ivars = nil
        value = Kernel.tick_count if value
  
        collection.each do |m|
          m_to_s = m.to_s
          self.instance_variable_set("@#{m_to_s}".to_sym, value) if m_to_s.strip.length > 0
        rescue Exception => e
          raise e, <<-S
  * ERROR:
  Attempted to set the a key on the DragonRuby GTK's Keyboard data
  structure, but the property isn't available for raw_key #{raw_key} #{m}.
  
  You should contact DragonRuby and tell them to associate the raw_key #{raw_key}
  with a friendly property name (we are open to suggestions if you have any).
  [GTK::KeyboardKeys#set, GTK::KeyboardKeys#char_to_method]
  
  S
        end
      end
  
      def method_missing m, *args
        if KeyboardKeys.method_to_key_hash[m.without_ending_bang]
          begin
            define_singleton_method(m) do
              r = self.instance_variable_get("@#{m.without_ending_bang}".to_sym)
              clear_key m
              return r
            end
  
            return self.send m
          rescue Exception => e
            log_important "#{e}"
          end
        end
  
        did_you_mean = KeyboardKeys.method_to_key_hash.find_all do |k, v|
          k.to_s[0..1] == m.to_s[0..1]
        end.map {|k, v| ":#{k} (#{v[:string_representation]})" }
        did_you_mean_string = ""
        did_you_mean_string = ". Did you mean #{did_you_mean.join ", "}?"
  
        raise <<-S
  * ERROR:
  #{KeyboardKeys.method_to_key_hash.map { |k, v| "** :#{k} #{v.string_representation}" }.join("\n")}
  
  There is no key on the keyboard called :#{m}#{did_you_mean_string}.
  Full list of available keys =:points_up:=.
  S
      end
  
      def serialize
        hash = super
        hash.delete(:scrubbed_ivars)
        hash[:truthy_keys] = self.truthy_keys
        hash
      end
    end
  end
  
  module GTK
    # @gtk
    class Keyboard
  
      # @return [KeyboardKeys]
      # @gtk
      attr_accessor :key_up
  
      # @return [KeyboardKeys]
      # @gtk
      attr_accessor :key_held
  
      # @return [KeyboardKeys]
      # @gtk
      attr_accessor :key_down
  
      # @return [Boolean]
      # @gtk
      attr_accessor :has_focus
  
      def initialize
        @key_up      = KeyboardKeys.new
        @key_held    = KeyboardKeys.new
        @key_down    = KeyboardKeys.new
        @has_focus   = false
      end
  
      def p
        @key_down.p || @key_held.p
      end
  
      # The left arrow or "a" was pressed.
      #
      # @return [Boolean]
      def left
        @key_up.left || @key_held.left || a
      end
  
      # The right arrow or "d" was pressed.
      #
      # @return [Boolean]
      def right
        @key_up.right || @key_held.right || d
      end
  
      # The up arrow or "w" was pressed.
      #
      # @return [Boolean]
      def up
        @key_up.up || @key_held.up || w
      end
  
      # The down arrow or "s" was pressed.
      #
      # @return [Boolean]
      def down
        @key_up.down || @key_held.down || s
      end
  
      # Clear all current key presses.
      #
      # @return [void]
      def clear
        @key_up.clear
        @key_held.clear
        @key_down.clear
      end
  
      def serialize
        {
          key_up: @key_up.serialize,
          key_held: @key_held.serialize,
          key_down: @key_down.serialize,
          has_focus: @has_focus
        }
      end
      alias_method :inspect, :serialize
  
      # @return [String]
      def to_s
        serialize.to_s
      end
  
      def key
        {
          down: @key_down.truthy_keys,
          held: @key_held.truthy_keys,
          down_or_held: (@key_down.truthy_keys + @key_held.truthy_keys).uniq,
          up: @key_up.truthy_keys,
        }
      end
      alias_method :keys, :key
  
      include DirectionalInputHelperMethods
    end
  end
  
  module GTK
    class MousePoint
      include GTK::Geometry
  
      # @gtk
      attr_accessor :x, :y, :point, :created_at, :global_created_at
  
      def initialize x, y
        @x = x
        @y = y
        @point = [x, y]
        @created_at = Kernel.tick_count
        @global_created_at = Kernel.global_tick_count
      end
  
      def w; 0; end
      def h; 0; end
      def left; x; end
      def right; x; end
      def top; y; end
      def bottom; y; end
  
      def created_at_elapsed
        @created_at.elapsed_time
      end
  
      def to_hash
        serialize
      end
  
      def serialize
        {
          x: @x,
          y: @y,
          created_at: @created_at,
          global_created_at: @global_created_at
        }
      end
  
      def inspect
        serialize.to_s
      end
  
      def to_s
        serialize.to_s
      end
    end
  
    # Provides access to the mouse.
    #
    # @gtk
    class Mouse
  
      # @gtk
      attr_accessor :moved,
                    :moved_at,
                    :global_moved_at,
                    :up, :has_focus,
                    :button_bits, :button_left,
                    :button_middle, :button_right,
                    :button_x1, :button_x2,
                    :wheel
  
      attr_accessor :click
      attr_accessor :previous_click
      attr_accessor :x
      attr_accessor :y
  
      def initialize
        @x = 0
        @y = 0
        @has_focus = false
        @button_bits = 0
        @button_left = false
        @button_middle = false
        @button_right = false
        @button_x1 = false
        @button_x2 = false
        clear
      end
  
      def point
        [@x, @y].point
      end
  
      def inside_rect? rect
        point.inside_rect? rect
      end
  
      def inside_circle? center, radius
        point.point_inside_circle? center, radius
      end
  
      def intersect_rect? other_rect
        { x: point.x, y: point.y, w: 0, h: 0 }.intersect_rect? other_rect
      end
  
      alias_method :position, :point
  
      def clear
        if @click
          @previous_click = MousePoint.new @click.point.x, @click.point.y
          @previous_click.created_at = @click.created_at
          @previous_click.global_created_at = @click.global_created_at
        end
  
        @click = nil
        @up    = nil
        @moved = nil
        @wheel = nil
      end
  
      def up
        @up
      end
  
      def down
        @click
      end
  
      def serialize
        result = {}
  
        if @click
          result[:click] = @click.to_hash
          result[:down] = @click.to_hash
        end
  
        result[:up] = @up.to_hash if @up
        result[:x] = @x
        result[:y] = @y
        result[:moved] = @moved
        result[:moved_at] = @moved_at
        result[:has_focus] = @has_focus
  
        result
      end
  
      def to_s
        serialize.to_s
      end
  
      alias_method :inspect, :to_s
    end
  
    # Provides access to multitouch input
    #
    # @gtk
    class FingerTouch
  
      # @gtk
      attr_accessor :moved,
                    :moved_at,
                    :global_moved_at,
                    :down_at,
                    :global_down_at,
                    :touch_order,
                    :first_tick_down,
                    :x, :y
  
      def initialize
        @moved = false
        @moved_at = 0
        @global_moved_at = 0
        @down_at = 0
        @global_down_at = 0
        @touch_order = 0
        @first_tick_down = true
        @x = 0
        @y = 0
      end
  
      def point
        [@x, @y].point
      end
  
      def inside_rect? rect
        point.inside_rect? rect
      end
  
      def inside_circle? center, radius
        point.point_inside_circle? center, radius
      end
  
      alias_method :position, :point
  
      def serialize
        result = {}
        result[:x] = @x
        result[:y] = @y
        result[:touch_order] = @touch_order
        result[:moved] = @moved
        result[:moved_at] = @moved_at
        result[:global_moved_at] = @global_moved_at
        result[:down_at] = @down_at
        result[:global_down_at] = @global_down_at
  
        result
      end
  
      def to_s
        serialize.to_s
      end
  
      alias_method :inspect, :to_s
    end
  end
  
  module GTK
    class Inputs
      attr_reader :controllers
      attr_reader :keyboard
      attr_reader :mouse
      attr_accessor :http_requests
      attr_reader :touch
      attr_accessor :finger_one, :finger_two
      attr_accessor :finger_left, :finger_right
      attr_accessor :text, :history
  
      def initialize
        @controllers = [Controller.new, Controller.new]
        @keyboard = Keyboard.new
        @mouse = Mouse.new
        @touch = {}
        @finger_one = nil
        @finger_two = nil
        @text = []
        @http_requests = []
      end
  
      def up
        keyboard.up ||
          (controller_one && controller_one.up)
      end
  
      def down
        keyboard.down ||
          (controller_one && controller_one.down)
      end
  
      def left
        keyboard.left ||
          (controller_one && controller_one.left)
      end
  
      def right
        keyboard.right ||
          (controller_one && controller_one.right)
      end
  
      def directional_vector
        keyboard.directional_vector ||
          (controller_one && controller_one.directional_vector)
      end
  
      def directional_angle
        keyboard.directional_angle || (controller_one && controller_one.directional_angle)
      end
  
      # Returns a signal indicating right (`1`), left (`-1`), or neither ('0').
      #
      # @return [Integer]
      def left_right
        return -1 if self.left
        return  1 if self.right
        return  0
      end
  
      # Returns a signal indicating up (`1`), down (`-1`), or neither ('0').
      #
      # @return [Integer]
      def up_down
        return  1 if self.up
        return -1 if self.down
        return  0
      end
  
      # Returns the coordinates of the last click.
      #
      # @return [Float, Float]
      def click
        return nil unless @mouse.click
        return @mouse.click.point
      end
  
      # The first controller.
      #
      # @return [Controller]
      def controller_one
        @controllers[0]
      end
  
      # The second controller.
      #
      # @return [Controller]
      def controller_two
        @controllers[1]
      end
  
      # Clears all inputs.
      #
      # @return [void]
      def clear
        @mouse.clear
        @keyboard.clear
        @controllers.each(&:clear)
        @touch.clear
        @http_requests.clear
        @finger_one = nil
        @finger_two = nil
      end
  
      # @return [Hash]
      def serialize
        {
          controller_one: controller_one.serialize,
          controller_two: controller_two.serialize,
          keyboard: keyboard.serialize,
          mouse: mouse.serialize,
          text: text.serialize
        }
      end
    end
  end

#+end_src

*** ios_wizard.rb
#+begin_src ruby
  # ./dragon/ios_wizard.rb
  # coding: utf-8
  # Copyright 2019 DragonRuby LLC
  # MIT License
  # ios_wizard.rb has been released under MIT (*only this file*).
  
  # Contributors outside of DragonRuby who also hold Copyright: Michał Dudziński
  
  class IOSWizard < Wizard
    def initialize
      @doctor_executed_at = 0
    end
  
    def relative_path
      (File.dirname $gtk.binary_path)
    end
  
    def steps
      @steps ||= []
    end
  
    def prerequisite_steps
      [
        :check_for_xcode,
        :check_for_brew,
        :check_for_certs,
      ]
    end
  
    def app_metadata_retrieval_steps
      [
        :determine_team_identifier,
        :determine_app_name,
        :determine_app_id,
      ]
    end
  
    def steps_development_build
      [
        *prerequisite_steps,
  
        :check_for_device,
        :check_for_dev_profile,
  
        *app_metadata_retrieval_steps,
        :determine_devcert,
  
        :clear_tmp_directory,
        :stage_app,
  
        :development_write_info_plist,
  
        :write_entitlements_plist,
        :compile_icons,
        :clear_payload_directory,
  
        :create_payload_directory_dev,
  
        :create_payload,
        :code_sign_payload,
  
        :create_ipa,
        :deploy
      ]
    end
  
    def steps_production_build
      [
        *prerequisite_steps,
  
        :check_for_distribution_profile,
        :determine_app_version,
  
        *app_metadata_retrieval_steps,
        :determine_prodcert,
  
        :clear_tmp_directory,
        :stage_app,
  
        :production_write_info_plist,
  
        :write_entitlements_plist,
        :compile_icons,
        :clear_payload_directory,
  
        :create_payload_directory_prod,
  
        :create_payload,
        :code_sign_payload,
  
        :create_ipa,
        :print_publish_help
      ]
    end
  
    def get_reserved_sprite png
      sprite_path = ".dragonruby/sprites/wizards/ios/#{png}"
  
      if !$gtk.ivar :rcb_release_mode
        sprite_path = "deploy_template/#{sprite_path}"
        $gtk.reset_sprite sprite_path
      end
  
      if !$gtk.read_file sprite_path
        log_error "png #{png} not found."
      end
  
      sprite_path
    end
  
    def start opts = nil
      @opts = opts || {}
  
      if !(@opts.is_a? Hash) || !($gtk.args.fn.eq_any? @opts[:env], :dev, :prod)
        raise WizardException.new(
                "* $wizards.ios.start needs to be provided an environment option.",
                "** For development builds type: $wizards.ios.start env: :dev",
                "** For production builds type: $wizards.ios.start env: :prod"
              )
      end
  
      @production_build = (@opts[:env] == :prod)
      @steps = steps_development_build
      @steps = steps_production_build if @production_build
      @certificate_name = nil
      @app_version = opts[:version]
      @app_version = "1.0" if @opts[:env] == :dev && !@app_version
      init_wizard_status
      log_info "Starting iOS Wizard so we can deploy to your device."
      @start_at = Kernel.global_tick_count
      steps.each do |m|
        log_info "Running step ~:#{m}~."
        result = (send m) || :success if @wizard_status[m][:result] != :success
        @wizard_status[m][:result] = result
        log_info "Running step ~:#{m}~ complete."
      end
      nil
    rescue Exception => e
      if e.is_a? WizardException
        $console.log.clear
        $console.archived_log.clear
        log "=" * $console.console_text_width
        e.console_primitives.each do |p|
          $console.add_primitive p
        end
        log "=" * $console.console_text_width
      else
        log_error e.to_s
        log e.__backtrace_to_org__
      end
  
      init_wizard_status
      $console.set_command "$wizards.ios.start env: :#{@opts[:env]}"
    end
  
    def always_fail
      return false if $gtk.ivar :rcb_release_mode
      return true
    end
  
    def check_for_xcode
      if !cli_app_exist?(xcodebuild_cli_app)
        raise WizardException.new(
          "* You need Xcode to use $wizards.ios.start.",
          { w: 75, h: 75, path: get_reserved_sprite("xcode.png") },
          "** 1. Go to http://developer.apple.com and register.",
          "** 2. Download Xcode 11.3+ from http://developer.apple.com/downloads.",
          "   NOTE: DO NOT install Xcode from the App Store. Use the link above.",
          { w: 700, h: 359, path: get_reserved_sprite("xcode-downloads.png") },
          "** 3. After installing. Open up Xcode to accept the EULA."
        )
      end
    end
  
    def check_for_brew
      if !cli_app_exist?('brew')
        raise WizardException.new(
          "* You need to install Brew.",
          { w: 700, h: 388, path: get_reserved_sprite("brew.png") },
          "** 1. Go to http://brew.sh.",
          "** 2. Copy the command that starts with `/bin/bash -c` on the site.",
          "** 3. Open Terminal and run the command you copied from the website.",
          { w: 700, h: 99, path: get_reserved_sprite("terminal.png") },
        )
      end
    end
  
    def init_wizard_status
      @wizard_status = {}
      steps.each do |m|
        @wizard_status[m] = { result: :not_started }
      end
  
      previous_step = nil
      next_step = nil
      steps.each_cons(2) do |current_step, next_step|
        @wizard_status[current_step][:next_step] = next_step
      end
  
      steps.reverse.each_cons(2) do |current_step, previous_step|
        @wizard_status[current_step][:previous_step] = previous_step
      end
    end
  
    def restart
      init_wizard_status
      start
    end
  
    def check_for_distribution_profile
      @provisioning_profile_path = "profiles/distribution.mobileprovision"
      if !($gtk.read_file @provisioning_profile_path)
        $gtk.system "mkdir -p #{relative_path}/profiles"
        $gtk.system "open #{relative_path}/profiles"
        $gtk.system "echo Download the mobile provisioning profile and place it here with the name distribution.mobileprovision > #{relative_path}/profiles/README.txt"
        raise WizardException.new(
          "* I didn't find a mobile provision.",
          "** 1. Go to http://developer.apple.com and click \"Certificates, IDs & Profiles\".",
          "** 2. Add an App Identifier.",
          "** 3. Select the App IDs option from the list.",
          { w: 700, h: 75, path: get_reserved_sprite("identifiers.png") },
          "** 4. Add your Device next. You can use idevice_id -l to get the UUID of your device.",
          { w: 365, h: 69, path: get_reserved_sprite("device-link.png") },
          "** 5. Create a Profile. Associate your certs, id, and device.",
          { w: 300, h: 122, path: get_reserved_sprite("profiles.png") },
          "** 6. Download the mobile provision and save it to 'profiles/development.mobileprovision'.",
          { w: 200, h: 124, path: get_reserved_sprite("profiles-folder.png") },
        )
      end
    end
  
    def check_for_dev_profile
      @provisioning_profile_path = "profiles/development.mobileprovision"
      if !($gtk.read_file @provisioning_profile_path)
        $gtk.system "mkdir -p #{relative_path}/profiles"
        $gtk.system "open #{relative_path}/profiles"
        $gtk.system "echo Download the mobile provisioning profile and place it here with the name development.mobileprovision > #{relative_path}/profiles/README.txt"
        raise WizardException.new(
          "* I didn't find a mobile provision.",
          "** 1. Go to http://developer.apple.com and click \"Certificates, IDs & Profiles\".",
          "** 2. Add an App Identifier.",
          "** 3. Select the App IDs option from the list.",
          { w: 700, h: 75, path: get_reserved_sprite("identifiers.png") },
          "** 4. Add your Device next. You can use idevice_id -l to get the UUID of your device.",
          { w: 365, h: 69, path: get_reserved_sprite("device-link.png") },
          "** 5. Create a Profile. Associate your certs, id, and device.",
          { w: 300, h: 122, path: get_reserved_sprite("profiles.png") },
          "** 6. Download the mobile provision and save it to 'profiles/development.mobileprovision'.",
          { w: 200, h: 124, path: get_reserved_sprite("profiles-folder.png") },
        )
      end
    end
  
    def provisioning_profile_path environment
      return "profiles/distribution.mobileprovision" if environment == :prod
      return "profiles/development.mobileprovision"
    end
  
    def ios_metadata_template
      <<-S
  # ios_metadata.txt is used by the Pro version of DragonRuby Game Toolkit to create iOS apps.
  # Information about the Pro version can be found at: http://dragonruby.org/toolkit/game#purchase
  
  # teamid needs to be set to your assigned Team Id which can be found at https://developer.apple.com/account/#/membership/
  teamid=
  # appid needs to be set to your application identifier which can be found at https://developer.apple.com/account/resources/identifiers/list
  appid=
  # appname is the name you want to show up underneath the app icon on the device. Keep it under 10 characters.
  appname=
  # devcert is the certificate to use for development/deploying to your local device. This is the NAME of the certificate as it's displayed in Keychain Access.
  devcert=
  # prodcert is the certificate to use for distribution to the app store. This is the NAME of the certificate as it's displayed in Keychain Access.
  prodcert=
  S
    end
  
    def ios_metadata
      contents = $gtk.read_file 'metadata/ios_metadata.txt'
  
      if !contents
        $gtk.write_file 'metadata/ios_metadata.txt', ios_metadata_template
        contents = $gtk.read_file 'metadata/ios_metadata.txt'
      end
  
      kvps = contents.each_line
                     .reject { |l| l.strip.length == 0 || (l.strip.start_with? "#") }
                     .map do |l|
                       key, value = l.split("=")
                       [key.strip.to_sym, value.strip]
                     end.flatten
      Hash[*kvps]
    end
  
    def game_metadata
      contents = $gtk.read_file 'metadata/game_metadata.txt'
  
      kvps = contents.each_line
                     .reject { |l| l.strip.length == 0 || (l.strip.start_with? "#") }
                     .map do |l|
                       key, value = l.split("=")
                       [key.strip.to_sym, value.strip]
                     end.flatten
      Hash[*kvps]
    end
  
    def raise_ios_metadata_required
      raise WizardException.new(
              "* mygame/metadata/ios_metadata.txt needs to be filled out.",
              "You need to update metadata/ios_metadata.txt with a valid teamid, appname, appid, devcert, and prodcert.",
              "Instructions for where the values should come from are within metadata/ios_metadata.txt."
            )
    end
  
    def determine_team_identifier
      @team_id = (ios_metadata.teamid || "")
      raise_ios_metadata_required if @team_id.strip.length == 0
      log_info "Team Identifer is: #{@team_id}"
    end
  
    def determine_app_name
      @app_name = (ios_metadata.appname || "")
      raise_ios_metadata_required if @app_name.strip.length == 0
      log_info "App name is: #{@app_name}."
    end
  
    def provisioning_profile_xml environment
      xml = $gtk.read_file (provisioning_profile_path environment)
      scrubbed = xml.each_line.map do |l|
        if l.strip.start_with? "<"
          if l.start_with? '</plist>'
            '</plist>'
          elsif l.include? "Apple Inc."
            nil
          elsif l.include? '<data>'
            nil
          else
            l
          end
        else
          nil
        end
      end.reject { |l| !l }.join
      $gtk.parse_xml scrubbed
    end
  
    def determine_app_id
      @app_id = ios_metadata.appid
      raise_ios_metadata_required if @app_id.strip.length == 0
      log_info "App Identifier is set to: #{@app_id}"
    end
  
    def determine_devcert
      @certificate_name = ios_metadata.devcert
      raise_ios_metadata_required if @certificate_name.strip.length == 0
      log_info "Dev Certificate is set to: #{@certificate_name}"
    end
  
    def determine_prodcert
      @certificate_name = ios_metadata.prodcert
      raise_ios_metadata_required if @certificate_name.strip.length == 0
      log_info "Production (Distribution) Certificate is set to: #{@certificate_name}"
    end
  
    def set_app_name name
      @app_name = name
      start
    end
  
    def set_dev_profile path
      if !$gtk.read_file path
        log_error "I couldn't find a development profile at #{path}."
        ask_for_dev_profile
      else
        @provisioning_profile_path = path
        start
      end
    end
  
    def clear_tmp_directory
      sh "rm -rf #{tmp_directory}"
    end
  
    def set_app_id id
      log_info = "App Id set to: #{id}"
      @app_id = id
      start
    end
  
    def check_for_device
      log_info "Looking for device."
  
      if !cli_app_exist?(idevice_id_cli_app)
        raise WizardException.new(
           "* It doesn't look like you have the libimobiledevice iOS protocol library installed.",
           "** 1. Open Terminal.",
           { w: 700, h: 99, path: get_reserved_sprite("terminal.png") },
           "** 2. Run: `brew install libimobiledevice`.",
           { w: 500, h: 93, path: get_reserved_sprite("brew-install-libimobiledevice.png") },
        )
      end
  
      if !cli_app_exist?(ideviceinstaller_cli_app)
        raise WizardException.new(
           "* It doesn't look like you have the libimobiledevice iOS protocol library installed.",
           "** 1. Open Terminal.",
           { w: 700, h: 99, path: get_reserved_sprite("terminal.png") },
           "** 2. Run: `brew install ideviceinstaller`.",
           { w: 500, h: 91, path: get_reserved_sprite("brew-install-ideviceinstaller.png") },
        )
      end
  
      if connected_devices.length == 0
        raise WizardException.new("* I couldn't find any connected devices. Connect your iOS device to your Mac and try again.")
      end
  
      @device_id = connected_devices.first
      log_info "I will be using device with UUID #{@device_id}"
    end
  
    def check_for_certs
      log_info "Attempting to find certificates on your computer."
  
      if @production_build
        @certificate_name = ios_metadata[:prodcert]
      else
        @certificate_name = ios_metadata[:devcert]
      end
  
      log_info "I will be using certificate: '#{@certificate_name}'."
    end
  
    def idevice_id_cli_app
      "idevice_id"
    end
  
    def ideviceinstaller_cli_app
      "ideviceinstaller"
    end
  
    def security_cli_app
      "/usr/bin/security"
    end
  
    def xcodebuild_cli_app
      "xcodebuild"
    end
  
    def connected_devices
      sh("idevice_id -l").strip.each_line.map do |l|
        l.strip
      end.reject { |l| l.length == 0 }
    end
  
    def cli_app_exist? app
      `which #{app}`.strip.length != 0
    end
  
    def write_entitlements_plist
      if @production_build
        entitlement_plist_string = <<-XML
  <?xml version="1.0" encoding="UTF-8"?>
  <!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
  <plist version="1.0">
          <dict>
                  <key>application-identifier</key>
                  <string>:app_id</string>
                  <key>beta-reports-active</key>
                  <true/>
          </dict>
  </plist>
  XML
      else
        entitlement_plist_string = <<-XML
  <?xml version="1.0" encoding="UTF-8"?>
  <!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
  <plist version="1.0">
          <dict>
                  <key>application-identifier</key>
                  <string>:app_id</string>
                  <key>get-task-allow</key>
                  <true/>
          </dict>
  </plist>
  XML
      end
  
      log_info "Creating Entitlements.plist"
  
      $gtk.write_file_root "tmp/ios/Entitlements.plist", entitlement_plist_string.gsub(":app_id", "#{@team_id}.#{@app_id}").strip
      $gtk.write_file_root "tmp/ios/Entitlements.txt", entitlement_plist_string.gsub(":app_id", "#{@team_id}.#{@app_id}").strip
  
      sh "/usr/bin/plutil -convert binary1 \"#{tmp_directory}/Entitlements.plist\""
      sh "/usr/bin/plutil -convert xml1 \"#{tmp_directory}/Entitlements.plist\""
  
      @entitlement_plist_written = true
    end
  
    def code_sign_payload
      log_info "Signing app with #{@certificate_name}."
  
      sh "CODESIGN_ALLOCATE=\"/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/codesign_allocate\" /usr/bin/codesign -f -s \"#{@certificate_name}\" --entitlements #{tmp_directory}/Entitlements.plist \"#{tmp_directory}/ipa_root/Payload/#{@app_name}.app\""
      sh "CODESIGN_ALLOCATE=\"/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/codesign_allocate\" /usr/bin/codesign -f -s \"#{@certificate_name}\" --entitlements #{tmp_directory}/Entitlements.plist \"#{tmp_directory}/ipa_root/Payload/#{@app_name}.app/#{@app_name}\""
  
      @code_sign_completed = true
    end
  
    def development_write_info_plist
      log_info "Adding Info.plist."
  
      info_plist_string = <<-XML
  <?xml version="1.0" encoding="UTF-8"?>
  <!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
  <plist version="1.0">
  <dict>
          <key>NSAppTransportSecurity</key>
          <dict>
                  <key>NSAllowsArbitraryLoads</key>
                  <true/>
                  <key>NSExceptionDomains</key>
                  <dict>
                          <key>google.com</key>
                          <dict>
                                  <key>NSExceptionAllowsInsecureHTTPLoads</key>
                                  <true/>
                                  <key>NSIncludesSubdomains</key>
                                  <true/>
                          </dict>
                  </dict>
          </dict>
          <key>BuildMachineOSBuild</key>
          <string>20D91</string>
          <key>CFBundleDevelopmentRegion</key>
          <string>en</string>
          <key>CFBundleDisplayName</key>
          <string>:app_name</string>
          <key>CFBundleExecutable</key>
          <string>:app_name</string>
          <key>CFBundleIconFiles</key>
          <array>
                  <string>AppIcon60x60</string>
          </array>
          <key>CFBundleIcons</key>
          <dict>
                  <key>CFBundlePrimaryIcon</key>
                  <dict>
                          <key>CFBundleIconFiles</key>
                          <array>
                                  <string>AppIcon60x60</string>
                          </array>
                          <key>CFBundleIconName</key>
                          <string>AppIcon</string>
                  </dict>
          </dict>
          <key>CFBundleIcons~ipad</key>
          <dict>
                  <key>CFBundlePrimaryIcon</key>
                  <dict>
                          <key>CFBundleIconFiles</key>
                          <array>
                                  <string>AppIcon60x60</string>
                                  <string>AppIcon76x76</string>
                                  <string>AppIcon83.5x83.5</string>
                          </array>
                          <key>CFBundleIconName</key>
                          <string>AppIcon</string>
                  </dict>
          </dict>
          <key>CFBundleIdentifier</key>
          <string>:app_id</string>
          <key>CFBundleInfoDictionaryVersion</key>
          <string>:app_version</string>
          <key>CFBundleName</key>
          <string>:app_name</string>
          <key>CFBundlePackageType</key>
          <string>APPL</string>
          <key>CFBundleShortVersionString</key>
          <string>:app_version</string>
          <key>CFBundleSignature</key>
          <string>????</string>
          <key>CFBundleSupportedPlatforms</key>
          <array>
                  <string>iPhoneOS</string>
          </array>
          <key>CFBundleVersion</key>
          <string>:app_version</string>
          <key>DTCompiler</key>
          <string>com.apple.compilers.llvm.clang.1_0</string>
          <key>DTPlatformBuild</key>
          <string>18D46</string>
          <key>DTPlatformName</key>
          <string>iphoneos</string>
          <key>DTPlatformVersion</key>
          <string>14.4</string>
          <key>DTSDKBuild</key>
          <string>18D46</string>
          <key>DTSDKName</key>
          <string>iphoneos14.4</string>
          <key>DTXcode</key>
          <string>0124</string>
          <key>DTXcodeBuild</key>
          <string>12D4e</string>
          <key>MinimumOSVersion</key>
          <string>14.4</string>
          <key>UIAppFonts</key>
          <array/>
          <key>UIBackgroundModes</key>
          <array/>
          <key>UIDeviceFamily</key>
          <array>
                  <integer>1</integer>
                  <integer>2</integer>
          </array>
          <key>UILaunchImages</key>
          <array>
                  <dict>
                          <key>UILaunchImageMinimumOSVersion</key>
                          <string>7.0</string>
                          <key>UILaunchImageName</key>
                          <string>Default-568h@2x</string>
                          <key>UILaunchImageOrientation</key>
                          <string>Portrait</string>
                          <key>UILaunchImageSize</key>
                          <string>{320, 568}</string>
                  </dict>
                  <dict>
                          <key>UILaunchImageMinimumOSVersion</key>
                          <string>7.0</string>
                          <key>UILaunchImageName</key>
                          <string>Default-667h@2x</string>
                          <key>UILaunchImageOrientation</key>
                          <string>Portrait</string>
                          <key>UILaunchImageSize</key>
                          <string>{375, 667}</string>
                  </dict>
                  <dict>
                          <key>UILaunchImageMinimumOSVersion</key>
                          <string>7.0</string>
                          <key>UILaunchImageName</key>
                          <string>Default-736h@3x</string>
                          <key>UILaunchImageOrientation</key>
                          <string>Portrait</string>
                          <key>UILaunchImageSize</key>
                          <string>{414, 736}</string>
                  </dict>
          </array>
          <key>UILaunchStoryboardName</key>
          <string>SimpleSplash</string>
          <key>UIRequiredDeviceCapabilities</key>
          <array>
                  <string>arm64</string>
          </array>
          <key>UIRequiresFullScreen</key>
          <true/>
          <key>UIStatusBarStyle</key>
          <string>UIStatusBarStyleDefault</string>
          <key>UISupportedInterfaceOrientations</key>
          <array>
                  <string>UIInterfaceOrientationLandscapeRight</string>
          </array>
  </dict>
  </plist>
  XML
  
      # <string>UIInterfaceOrientationPortrait</string>
      # <string>UIInterfaceOrientationLandscapeRight</string>
  
      info_plist_string.gsub!(":app_name", @app_name)
      info_plist_string.gsub!(":app_id", @app_id)
  
      $gtk.write_file_root "tmp/ios/#{@app_name}.app/Info.plist", info_plist_string.strip
      $gtk.write_file_root "tmp/ios/Info.txt", info_plist_string.strip
  
      @info_plist_written = true
    end
  
    def production_write_info_plist
      log_info "Adding Info.plist."
  
      info_plist_string = <<-XML
  <?xml version="1.0" encoding="UTF-8"?>
  <!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
  <plist version="1.0">
  <dict>
          <key>BuildMachineOSBuild</key>
          <string>20D91</string>
          <key>CFBundleDevelopmentRegion</key>
          <string>en</string>
          <key>CFBundleDisplayName</key>
          <string>:app_name</string>
          <key>CFBundleExecutable</key>
          <string>:app_name</string>
          <key>CFBundleIconFiles</key>
          <array>
                  <string>AppIcon60x60</string>
          </array>
          <key>CFBundleIcons</key>
          <dict>
                  <key>CFBundlePrimaryIcon</key>
                  <dict>
                          <key>CFBundleIconFiles</key>
                          <array>
                                  <string>AppIcon60x60</string>
                          </array>
                          <key>CFBundleIconName</key>
                          <string>AppIcon</string>
                  </dict>
          </dict>
          <key>CFBundleIcons~ipad</key>
          <dict>
                  <key>CFBundlePrimaryIcon</key>
                  <dict>
                          <key>CFBundleIconFiles</key>
                          <array>
                                  <string>AppIcon60x60</string>
                                  <string>AppIcon76x76</string>
                                  <string>AppIcon83.5x83.5</string>
                          </array>
                          <key>CFBundleIconName</key>
                          <string>AppIcon</string>
                  </dict>
          </dict>
          <key>CFBundleIdentifier</key>
          <string>:app_id</string>
          <key>CFBundleInfoDictionaryVersion</key>
          <string>:app_version</string>
          <key>CFBundleName</key>
          <string>:app_name</string>
          <key>CFBundlePackageType</key>
          <string>APPL</string>
          <key>CFBundleShortVersionString</key>
          <string>:app_version</string>
          <key>CFBundleSignature</key>
          <string>????</string>
          <key>CFBundleSupportedPlatforms</key>
          <array>
                  <string>iPhoneOS</string>
          </array>
          <key>CFBundleVersion</key>
          <string>:app_version</string>
          <key>DTCompiler</key>
          <string>com.apple.compilers.llvm.clang.1_0</string>
          <key>DTPlatformBuild</key>
          <string>18D46</string>
          <key>DTPlatformName</key>
          <string>iphoneos</string>
          <key>DTPlatformVersion</key>
          <string>14.4</string>
          <key>DTSDKBuild</key>
          <string>18D46</string>
          <key>DTSDKName</key>
          <string>iphoneos14.4</string>
          <key>DTXcode</key>
          <string>0124</string>
          <key>DTXcodeBuild</key>
          <string>12D4e</string>
          <key>MinimumOSVersion</key>
          <string>14.4</string>
          <key>UIAppFonts</key>
          <array/>
          <key>UIBackgroundModes</key>
          <array/>
          <key>UIDeviceFamily</key>
          <array>
                  <integer>1</integer>
                  <integer>2</integer>
          </array>
          <key>UILaunchImages</key>
          <array>
                  <dict>
                          <key>UILaunchImageMinimumOSVersion</key>
                          <string>7.0</string>
                          <key>UILaunchImageName</key>
                          <string>Default-568h@2x</string>
                          <key>UILaunchImageOrientation</key>
                          <string>Portrait</string>
                          <key>UILaunchImageSize</key>
                          <string>{320, 568}</string>
                  </dict>
                  <dict>
                          <key>UILaunchImageMinimumOSVersion</key>
                          <string>7.0</string>
                          <key>UILaunchImageName</key>
                          <string>Default-667h@2x</string>
                          <key>UILaunchImageOrientation</key>
                          <string>Portrait</string>
                          <key>UILaunchImageSize</key>
                          <string>{375, 667}</string>
                  </dict>
                  <dict>
                          <key>UILaunchImageMinimumOSVersion</key>
                          <string>7.0</string>
                          <key>UILaunchImageName</key>
                          <string>Default-736h@3x</string>
                          <key>UILaunchImageOrientation</key>
                          <string>Portrait</string>
                          <key>UILaunchImageSize</key>
                          <string>{414, 736}</string>
                  </dict>
          </array>
          <key>UILaunchStoryboardName</key>
          <string>SimpleSplash</string>
          <key>UIRequiredDeviceCapabilities</key>
          <array>
                  <string>arm64</string>
          </array>
          <key>UIRequiresFullScreen</key>
          <true/>
          <key>UIStatusBarStyle</key>
          <string>UIStatusBarStyleDefault</string>
          <key>UISupportedInterfaceOrientations</key>
          <array>
                  <string>UIInterfaceOrientationLandscapeRight</string>
          </array>
  </dict>
  </plist>
  XML
  
      # <string>UIInterfaceOrientationPortrait</string>
      # <string>UIInterfaceOrientationLandscapeRight</string>
  
      info_plist_string.gsub!(":app_name", @app_name)
      info_plist_string.gsub!(":app_id", @app_id)
      info_plist_string.gsub!(":app_version", @app_version)
  
      $gtk.write_file_root "tmp/ios/#{@app_name}.app/Info.plist", info_plist_string.strip
      $gtk.write_file_root "tmp/ios/Info.txt", info_plist_string.strip
  
      @info_plist_written = true
    end
  
    def device_orientation_xml
      return "UIInterfaceOrientationLandscapeRight" if $gtk.logical_width > $gtk.logical_height
      return "UIInterfaceOrientationPortrait"
    end
  
    def tmp_directory
      "#{relative_path}/tmp/ios"
    end
  
    def app_path
      "#{tmp_directory}/#{@app_name}.app"
    end
  
    def root_folder
      "#{relative_path}/#{$gtk.cli_arguments[:dragonruby]}"
    end
  
    def embed_mobileprovision
      sh %Q[cp #{@provisioning_profile_path} "#{app_path}/embedded.mobileprovision"]
      sh %Q[/usr/bin/plutil -convert binary1 "#{app_path}/Info.plist"]
    end
  
    def clear_payload_directory
      sh %Q[rm "#{@app_name}".ipa]
      sh %Q[rm -rf "#{app_path}/app"]
      sh %Q[rm -rf "#{app_path}/sounds"]
      sh %Q[rm -rf "#{app_path}/sprites"]
      sh %Q[rm -rf "#{app_path}/data"]
      sh %Q[rm -rf "#{app_path}/fonts"]
      sh %Q[rm -rf "#{app_path}/metadata"]
    end
  
    def stage_app
      log_info "Staging."
      sh "mkdir -p #{tmp_directory}"
      sh "cp -R #{relative_path}/dragonruby-ios.app/ \"#{tmp_directory}/#{@app_name}.app/\""
      sh "mv \"#{tmp_directory}/#{@app_name}.app/Runtime\" \"#{tmp_directory}/#{@app_name}.app/#{@app_name}\""
      sh %Q[cp -r "#{root_folder}/app/" "#{app_path}/app/"]
      sh %Q[cp -r "#{root_folder}/sounds/" "#{app_path}/sounds/"]
      sh %Q[cp -r "#{root_folder}/sprites/" "#{app_path}/sprites/"]
      sh %Q[cp -r "#{root_folder}/data/" "#{app_path}/data/"]
      sh %Q[cp -r "#{root_folder}/fonts/" "#{app_path}/fonts/"]
      sh %Q[cp -r "#{root_folder}/metadata/" "#{app_path}/metadata/"]
    end
  
    def create_payload
      sh %Q[mkdir -p #{tmp_directory}/ipa_root/Payload]
      sh %Q[cp -r "#{app_path}" "#{tmp_directory}/ipa_root/Payload"]
      sh %Q[chmod -R 755 "#{tmp_directory}/ipa_root/Payload"]
    end
  
    def create_payload_directory_dev
      # write dev machine's ip address for hotloading
      $gtk.write_file "app/server_ip_address.txt", $gtk.ffi_misc.get_local_ip_address.strip
  
      embed_mobileprovision
      clear_payload_directory
      stage_app
    end
  
    def create_payload_directory_prod
      # production builds does not hotload ip address
      sh %Q[rm "#{root_folder}/app/server_ip_address.txt"]
  
      embed_mobileprovision
      stage_app
  
      # production build marker
      sh %Q[mkdir -p "#{app_path}/metadata/"]
      sh %Q[touch "#{app_path}/metadata/DRAGONRUBY_PRODUCTION_BUILD"]
    end
  
    def create_ipa
      do_zip
      sh "cp \"#{tmp_directory}/ipa_root/archive.zip\" \"#{tmp_directory}/#{@app_name}.ipa\""
    end
  
    def do_zip
      $gtk.write_file_root "tmp/ios/do_zip.sh", <<-SCRIPT
  pushd #{tmp_directory}/ipa_root/
  zip -q -r archive.zip Payload
  popd
  SCRIPT
  
      sh "sh #{tmp_directory}/do_zip.sh"
    end
  
    def sh cmd
      log_info cmd.strip
      result = `#{cmd}`
      if result.strip.length > 0
        log_info result.strip.each_line.map(&:strip).join("\n")
      end
      result
    end
  
    def deploy
      sh "ideviceinstaller -i \"#{tmp_directory}/#{@app_name}.ipa\""
      log_info "Check your device!!"
    end
  
    def print_publish_help
      has_transporter = (sh "ls /Applications/Transporter.app").include? "Contents"
      if !has_transporter
        $gtk.openurl "https://apps.apple.com/us/app/transporter/id1450874784?mt=12"
        $console.set_command "$wizards.ios.start env: :#{@opts[:env]}, version: \"#{@opts[:version]}\""
        raise WizardException.new(
          "* To upload your app, Download Transporter from the App Store https://apps.apple.com/us/app/transporter/id1450874784?mt=12."
        )
      else
        sh "mkdir ./tmp/ios/intermediary_artifacts"
        sh "mv \"#{tmp_directory}/#{@app_name}.app\" #{tmp_directory}/intermediary_artifacts/"
        sh "mv \"#{tmp_directory}/do_zip.sh\" #{tmp_directory}/intermediary_artifacts"
        sh "mv \"#{tmp_directory}/Entitlements.plist\" #{tmp_directory}/intermediary_artifacts"
        sh "mv \"#{tmp_directory}/ipa_root\" #{tmp_directory}/intermediary_artifacts/"
        sh "open /Applications/Transporter.app"
        sh "open ./tmp/ios/"
      end
    end
  
    def compile_icons
      cmd = <<-S
  "/Applications/Xcode.app/Contents/Developer/usr/bin/actool" --output-format human-readable-text \
                                                              --notices --warnings --platform iphoneos \
                                                              --minimum-deployment-target 10.3 \
                                                              --target-device iphone \
                                                              --target-device ipad  --app-icon 'AppIcon' \
                                                              --output-partial-info-plist '#{app_path}/AssetCatalog-Info.plist' \
                                                              --compress-pngs --compile "#{app_path}" \
                                                              "#{app_path}/Assets.xcassets"
  S
      sh cmd
    end
  
    def stage_native_libs
      sh "cp -r \"#{root_folder}/native/\" \"#{app_path}/native/\""
      sh "CODESIGN_ALLOCATE=\"/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/codesign_allocate\" /usr/bin/codesign -f -s \"#{@certificate_name}\" --entitlements #{tmp_directory}/Entitlements.plist \"#{tmp_directory}/#{@app_name}.app/native/ios-device/ext.dylib\""
    end
  
    def set_version version
      @app_version = version
      start env: @opts[:env], version: version
    end
  
    def app_version
      log_info "Attempting to retrieve App Version from metadata/ios_metadata.txt."
      ios_version_number = (ios_metadata.version || "").strip
      if ios_version_number.length == 0
        log_info "Not found. Attempting to retrieve App Version from metadata/game_metadata.txt."
        ios_version_number = (game_metadata.version || "").strip
      end
      ios_version_number
    end
  
    def determine_app_version
      @app_version = app_version
      return if @app_version
    end
  end

#+end_src

*** itch_wizard.rb
#+begin_src ruby
  # ./dragon/itch_wizard.rb
  # coding: utf-8
  # Copyright 2019 DragonRuby LLC
  # MIT License
  # itch_wizard.rb has been released under MIT (*only this file*).
  
  class ItchWizard < Wizard
    def steps
      [
        :check_metadata,
        :deploy,
      ]
    end
  
    def write_blank_metadata
        $gtk.write_file metadata_file_path, <<-S.strip
  #devid=myname
  #devtitle=My Name
  #gameid=mygame
  #gametitle=My Game
  #version=0.1
  #icon=metadata/icon.png
  S
    end
  
    def check_metadata
      metadata_text = $gtk.read_file metadata_file_path
      if !metadata_text
        write_blank_metadata
      end
  
      if metadata_text.strip.each_line.to_a.length < 6
        write_blank_metadata
      end
  
      log "* INFO: Contents of #{metadata_file_path}:"
      log "#+begin_src txt"
      metadata_text.each_line { |l| log "  #{l}" }
      log "#+end_src"
      metadata = get_metadata
  
      if metadata[:dev_id].start_with?("#") || !@dev_id
        log "* PROMPT: Please provide your username for Itch."
        $console.set_command "$wizards.itch.set_dev_id \"#{metadata[:dev_id]}\""
        return :need_dev_id
      end
  
      if metadata[:dev_title].start_with?("#") || !@dev_title
        log "* PROMPT: Please provide developer's/company's name that you want displayed."
        $console.set_command "$wizards.itch.set_dev_title \"#{metadata[:dev_title]}\""
        return :need_dev_title
      end
  
      if metadata[:game_id].start_with?("#") || !@game_id
        log "* PROMPT: Please provide the id for you game. This is the id you specified when you set up a new game page on Itch."
        $console.set_command "$wizards.itch.set_game_id \"#{metadata[:game_id]}\""
        return :need_game_id
      end
  
      if metadata[:game_title].start_with?("#") || !@game_title
        log "* PROMPT: Please provide the display name for your game. (This can include spaces)"
        $console.set_command "$wizards.itch.set_game_title \"#{metadata[:game_title]}\""
        return :need_game_title
      end
  
      if metadata[:version].start_with?("#") || !@version
        log "* PROMPT: Please provide the version for your game."
        $console.set_command "$wizards.itch.set_version \"#{metadata[:version]}\""
        return :need_version
      end
  
      if metadata[:icon].start_with?("#") || !@icon
        log "* PROMPT: Please provide icon path for your game."
        $console.set_command "$wizards.itch.set_icon \"#{metadata[:icon]}\""
        return :need_icon
      end
  
      puts "here!! success!!!"
  
      return :success
    end
  
    def set_dev_id value
      @dev_id = value
      start
    end
  
    def set_dev_title value
      @dev_title = value
      start
    end
  
    def set_game_id value
      @game_id = value
      start
    end
  
    def set_game_title value
      @game_title = value
      start
    end
  
    def set_version value
      @version = value
      start
    end
  
    def set_icon value
      @icon = value
      write_metadata
      start
    end
  
    def write_metadata
      text = ""
      if @dev_id
        text += "devid=#{@dev_id}\n"
      else
        text += "#devid=myname\n"
      end
  
      if @dev_title
        text += "devtitle=#{@dev_title}\n"
      else
        text += "#devtitle=My Name\n"
      end
  
      if @game_id
        text += "gameid=#{@game_id}\n"
      else
        text += "#gameid=gameid\n"
      end
  
      if @game_title
        text += "gametitle=#{@game_title}\n"
      else
        text += "#gametitle=Game Name\n"
      end
  
      if @version
        text += "version=#{@version}\n"
      else
        text += "#version=0.1\n"
      end
  
      if @icon
        text += "icon=#{@icon}\n"
      else
        text += "#icon=metadata/icon.png\n"
      end
  
      $gtk.write_file metadata_file_path, text
    end
  
    def relative_path
      (File.dirname $gtk.binary_path)
    end
  
    def package_command
      "#{File.join $gtk.get_base_dir, 'dragonruby-publish'}"
    end
  
    def deploy
      log_info "* Running dragonruby-publish: #{package_command}"
      $gtk.openurl "http://itch.io/dashboard" if $gtk.platform == "Mac OS X"
      if $gtk.platform? :mac
        $gtk.exec "rm -rf ./builds"
      end
      results = $gtk.exec "#{package_command} --only-package"
      puts File.expand_path("./builds")
  
      log "#+begin_src"
      log results
      log "#+end_src"
  
      if $gtk.platform? :mac
        $gtk.exec "open ./builds/"
      elsif $gtk.platform? :windows
        $gtk.exec "powershell \"ii .\""
      end
  
      $gtk.openurl "https://itch.io/dashboard"
  
      :success
    end
  
    def start
      log "================"
      log "* INFO: Starting Itch Wizard."
      @start_at = Kernel.global_tick_count
      steps.each do |m|
        begin
          log_info "Running Itch Wizard Step: ~$wizards.itch.#{m}~"
          result = (send m) || :success
          @wizard_status[m][:result] = result
          if result != :success
            log_info "Exiting wizard. :#{result}"
            break
          end
        rescue Exception => e
          if e.is_a? WizardException
            $console.log.clear
            $console.archived_log.clear
            log "=" * $console.console_text_width
            e.console_primitives.each do |p|
              $console.add_primitive p
            end
            log "=" * $console.console_text_width
            $console.set_command (e.console_command || "$wizards.itch.start")
          else
            log_error "Step #{m} failed."
            log_error e.to_s
            $console.set_command "$wizards.itch.start"
          end
  
          break
        end
      end
    end
  
    def reset
      @dev_id = nil
      @dev_title = nil
      @game_id = nil
      @game_title = nil
      @version = nil
      @icon = nil
      init_wizard_status
    end
  
    def restart
      reset
      start
    end
  
    def initialize
      reset
    end
  
    def init_wizard_status
      @wizard_status = {}
  
      steps.each do |m|
        @wizard_status[m] = { result: :not_started }
      end
  
      previous_step = nil
      next_step = nil
  
      steps.each_cons(2) do |current_step, next_step|
        @wizard_status[current_step][:next_step] = next_step
      end
  
      steps.reverse.each_cons(2) do |current_step, previous_step|
        @wizard_status[current_step][:previous_step] = previous_step
      end
    end
  end

#+end_src

*** layout.rb
#+begin_src ruby
  # ./dragon/layout.rb
  # coding: utf-8
  # Copyright 2019 DragonRuby LLC
  # MIT License
  # layout.rb has been released under MIT (*only this file*).
  
  module GTK
    class Margin
      attr :left, :right, :top, :bottom
  
      def initialize
        @left   = 0
        @right  = 0
        @top    = 0
        @bottom = 0
      end
  
      def serialize
        {
          left:   @left,
          right:  @right,
          top:    @top,
          bottom: @bottom,
        }
      end
  
      def inspect
        serialize.to_s
      end
  
      def to_s
        serialize.to_s
      end
    end
  
    class SafeArea
      attr :w, :h, :margin
  
      def initialize
        @w      = 0
        @h      = 0
        @margin = Margin.new
      end
  
      def serialize
        {
          w:      @w,
          h:      @h,
          margin: @margin.serialize
        }
      end
  
      def inspect
        serialize.to_s
      end
  
      def to_s
        serialize.to_s
      end
    end
  
    class GridArea
      attr :w, :h, :margin, :gutter, :col_count, :row_count, :cell_w, :cell_h, :outer_gutter
  
      def initialize
        @w            = 0
        @h            = 0
        @gutter       = 0
        @outer_gutter = 0
        @col_count    = 0
        @row_count    = 0
        @margin       = Margin.new
      end
  
      def serialize
        {
          w:            @w,
          h:            @h,
          gutter:       @gutter,
          outer_gutter: @outer_gutter,
          col_count:    @col_count,
          row_count:    @row_count,
          margin:       @margin.serialize
        }
      end
  
      def inspect
        serialize.to_s
      end
  
      def to_s
        serialize.to_s
      end
    end
  
    class ControlArea
      attr :cell_size, :w, :h, :margin
  
      def initialize
        @margin = Margin.new
      end
  
      def serialize
        {
          cell_size: @cell_size,
          w:         @w,
          h:         @h,
          margin:    @margin.serialize,
        }
      end
  
      def inspect
        serialize.to_s
      end
  
      def to_s
        serialize.to_s
      end
    end
  
    class Device
      attr :w, :h, :safe_area, :grid_area, :control_area, :name, :aspect
  
      def initialize
        @name         = ""
        @w            = 0
        @h            = 0
        @safe_area    = SafeArea.new
        @grid_area    = GridArea.new
        @control_area = ControlArea.new
        @aspect       = AspectRatio.new
      end
  
      def assert! result, message
        return if result
        raise message
      end
  
      def check_math!
        assert! (@control_area.w + @control_area.margin.left + @control_area.margin.right) == @w, "Math for Width didn't pan out."
        assert! (@control_area.h + @control_area.margin.top + @control_area.margin.bottom) == @h, "Math for Height didn't pan out."
      end
  
      def serialize
        {
          name:         @name,
          w:            @w,
          h:            @h,
          aspect:       @aspect.serialize,
          safe_area:    @safe_area.serialize,
          grid_area:    @grid_area.serialize,
          control_area: @control_area.serialize
        }
      end
  
      def inspect
        serialize.to_s
      end
  
      def to_s
        serialize.to_s
      end
    end
  
    class AspectRatio
      attr :w, :h, :u
  
      def initialize
        @w = 0
        @h = 0
        @u = 0
      end
  
      def serialize
        {
          w: @w,
          h: @h,
          u: @u
        }
      end
  
      def inspect
        serialize.to_s
      end
  
      def to_s
        serialize.to_s
      end
    end
  
    class Layout
      attr :w, :h, :rect_cache
  
      def initialize w, h
        @w = w
        @h = h
        @rect_cache = {}
        init_device @w, @h
      end
  
      def u_for_16x9 w, h
        u = (w.fdiv 16).floor
        u = (h.fdiv 9).floor if (u * 9) > h
  
        {
          u: u,
          w: u * 16,
          h: u * 9
        }
      end
  
      def font_relative_size_enum size_enum
        base_line_logical = 22
        base_line_actual = font_size_med
        target_logical = size_enum
        target_logical = 1 if target_logical <= 0
        (base_line_actual / base_line_logical) * target_logical
      end
  
      def font_px_to_pt px
        (px / 1.33333).floor
      end
  
      def font_pt_to_px pt
        pt * 1.333333
      end
  
      def font_size_cell
        (cell_height / 1.33333)
      end
  
      def font_size_xl
        font_size_cell
      end
  
      def font_size_lg
        font_size_cell * 0.8
      end
  
      def font_size_med
        font_size_cell * 0.7
      end
  
      def font_size_sm
        font_size_cell * 0.6
      end
  
      def font_size_xs
        font_size_cell * 0.5
      end
  
      def font_size
        font_size_cell * 0.7
      end
  
      def logical_rect
        @logical_rect ||= { x: 0,
                            y: 0,
                            w: @w,
                            h: @h }
      end
  
      def safe_rect
        @safe_rect ||= { x: 0,
                         y: 0,
                         w: @w,
                         h: @h }
      end
  
      def control_rect
        @control_rect ||= { x: device.control_area.margin.left,
                            y: device.control_area.margin.top,
                            w: device.control_area.w,
                            h: device.control_area.h }
      end
  
      def row_count
        device.grid_area.row_count
      end
  
      def row_max_index
        row_count - 1
      end
  
      def col_count
        device.grid_area.col_count
      end
  
      def col_max_index
        col_count - 1
      end
  
      def gutter_height
        device.grid_area.gutter
      end
  
      def gutter_width
        device.grid_area.gutter
      end
  
      def outer_gutter
        device.grid_area.outer_gutter
      end
  
      def cell_height
        device.control_area.cell_size
      end
  
      def cell_width
        device.control_area.cell_size
      end
  
      def rect_defaults
        {
          row:      nil,
          col:      nil,
          h:        1,
          w:        1,
          dx:       0,
          dx_ratio: 1,
          dy:       0,
          dy_ratio: 1,
          dh_ratio: 1,
          dw_ratio: 1,
          merge:    nil,
          rect:     :control_rect
        }
      end
  
      def row n
        (rect row: n, col: 0, w: 0, h: 0).x
      end
  
      def row_from_bottom n
        (rect row: row_count - n, col: 0, w: 0, h: 0).x
      end
  
      def col n
        (rect row: 0, col: n, w: 0, h: 0).y
      end
  
      def col_from_right n
        (rect row: 0, col: col_max_index - n, w: 0, h: 0).y
      end
  
      def w n
        (rect row: 0, col: 0, w: n, h: 1).w
      end
  
      def h n
        (rect row: 0, col: 0, w: 1, h: n).h
      end
  
      def rect_group opts
        group = opts.group
        r     = opts.row || 0
        r     = row_max_index - opts.row_from_bottom if opts.row_from_bottom
        c     = opts.col || 0
        c     = col_max_index - opts.col_from_right  if opts.col_from_right
        drow  = opts.drow || 0
        dcol  = opts.dcol || 0
        w     = opts.w    || 0
        h     = opts.h    || 0
        merge = opts[:merge]
  
        running_row = r
        running_col = c
  
        running_col = calc_col_offset(opts.col_offset) if opts.col_offset
        running_row = calc_row_offset(opts.row_offset) if opts.row_offset
  
        group.map do |i|
          group_layout_opts = i.layout || {}
          group_layout_opts = group_layout_opts.merge row: running_row,
                                                      col: running_col,
                                                      merge: merge,
                                                      w: w, h: h
          result = (rect group_layout_opts).merge i
  
          if (i.is_a? Hash) && (i.primitive_marker == :label)
            if    i.alignment_enum == 1
              result.x += result.w.half
            elsif i.alignment_enum == 2
              result.x += result.w
            end
          end
  
          running_row += drow
          running_col += dcol
          result
        end
      end
  
      def calc_row_offset opts = {}
        count = opts[:count] || opts[:length] || 0
        h     = opts.h || 1
        (row_count - (count * h)) / 2.0
      end
  
      def calc_col_offset opts = {}
        count = opts[:count] || opts[:length] || 0
        w     = opts.w || 1
        (col_count - (count * w)) / 2.0
      end
  
      def point opts = {}
        opts.w = 1
        opts.h = 1
        opts.row ||= 0
        opts.col ||= 0
        r = rect opts
        r.x  += r.w * opts.col_anchor if opts.col_anchor
        r.y  += r.h * opts.row_anchor if opts.row_anchor
        r
      end
  
      def rect *all_opts
        if all_opts.length == 1
          opts = all_opts.first
        else
          opts = {}
          all_opts.each do |o|
            opts.merge! o
          end
        end
  
        opts.row = row_max_index - opts.row_from_bottom if opts.row_from_bottom
        opts.col = col_max_index - opts.col_from_right if opts.col_from_right
        opts = rect_defaults.merge opts
        opts.row ||= 0
        opts.col ||= 0
  
        result = send opts[:rect]
        if opts[:row] && opts[:col] && opts[:w] && opts[:h]
          col = rect_col opts[:col], opts[:w]
          row = rect_row opts[:row], opts[:h]
          result = control_rect.merge x: col.x,
                                      y: row.y,
                                      w: col.w,
                                      h: row.h,
                                      center_x: col.center_x,
                                      center_y: row.center_y
        elsif opts[:row] && !opts[:col]
          result = rect_row opts[:row], opts[:h]
        elsif !opts[:row] && opts[:col]
          result = rect_col opts[:col], opts[:w]
        else
          raise "LayoutTheory::rect unable to process opts #{opts}."
        end
  
        if opts[:max_height] && opts[:max_height] >= 0
          if result[:h] > opts[:max_height]
            delta = (result[:h] - opts[:max_height]) * 2
            result[:y] += delta
            result[:h] = opts[:max_height]
          end
        end
  
        if opts[:max_width] && opts[:max_width] >= 0
          if result[:w] > opts[:max_width]
            delta = (result[:w] - opts[:max_width]) * 2
            result[:x] += delta
            result[:w] = opts[:max_width]
          end
        end
  
        result[:x] += opts[:dx]
        result[:y] += opts[:dy]
  
        if opts[:include_row_gutter]
          result[:x] -= device.grid_area.gutter
          result[:w] += device.grid_area.gutter * 2
        end
  
        if opts[:include_col_gutter]
          result[:y] -= device.grid_area.gutter
          result[:h] += device.grid_area.gutter * 2
        end
  
        result[:x] += opts[:dx]       if opts[:dx]
        result[:x] *= opts[:dx_ratio] if opts[:dx_ratio]
        result[:y] += opts[:dy]       if opts[:dy]
        result[:y] *= opts[:dy_ratio] if opts[:dy_ratio]
        result[:w] += opts[:dw]       if opts[:dw]
        result[:w] *= opts[:dw_ratio] if opts[:dw_ratio]
        result[:h] += opts[:dh]       if opts[:dh]
        result[:h] *= opts[:dh_ratio] if opts[:dh_ratio]
        result.merge! opts[:merge]    if opts[:merge]
        result[:row] = opts[:row]
        result[:col] = opts[:col]
  
        result[:h] = result[:h].clamp 0
        result[:w] = result[:w].clamp 0
  
        if $gtk.args.grid.name == :center
          result[:x] -= 640
          result[:y] -= 360
        end
  
        result
      end
  
      def rect_center reference, target
        delta_x = (reference.w - target.w).fdiv 2
        delta_y = (reference.h - target.h).fdiv 2
        [target.x - delta_x, target.y - delta_y, target.w, target.h]
      end
  
      def rect_row index, h
        @rect_cache[:row] ||= {}
        @rect_cache[:row][index] ||= {}
        return @rect_cache[:row][index][h] if @rect_cache[:row][index][h]
        row_h = (device.grid_area.gutter * (h - 1)) +
                (device.control_area.cell_size * h)
  
        row_h = row_h.to_i
        row_h -= 1 if row_h.odd?
  
        row_y = (control_rect.y) +
                (device.grid_area.gutter * index) +
                (device.control_area.cell_size * index)
  
        row_y = row_y.to_i
        row_y += 1 if row_y.odd? && (index + 1) > @device.grid_area.row_count.half
        row_y += 1 if row_y.odd? && (index + 1) <= @device.grid_area.row_count.half
  
        row_y = device.h - row_y - row_h
  
        result = control_rect.merge y: row_y, h: row_h, center_y: (row_y + row_h.half)
        @rect_cache[:row][index][h] = result
        @rect_cache[:row][index][h]
      end
  
      def rect_col index, w
        @rect_cache[:col] ||= {}
        @rect_cache[:col][index] ||= {}
        return @rect_cache[:col][index][w] if @rect_cache[:col][index][w]
        col_x = (control_rect.x) +
                (device.grid_area.gutter * index) +
                (device.control_area.cell_size * index)
  
        col_x = col_x.to_i
        col_x -= 1 if col_x.odd? && (index + 1) < @device.grid_area.col_count.half
        col_x += 1 if col_x.odd? && (index + 1) >= @device.grid_area.col_count.half
  
        col_w = (device.grid_area.gutter * (w - 1)) +
                (device.control_area.cell_size * w)
  
        col_w = col_w.to_i
        col_w -= 1 if col_w.odd?
  
        result = control_rect.merge x: col_x, w: col_w, center_x: (col_x + col_w.half)
        @rect_cache[:col][index][w] = result
        @rect_cache[:col][index][w]
      end
  
      def device
        @device
      end
  
      def init_device w, h
        @device      = Device.new
        @device.w    = w
        @device.h    = h
        @device.name = "Device"
        @device.aspect.w = (u_for_16x9 w, h)[:w]
        @device.aspect.h = (u_for_16x9 w, h)[:h]
        @device.aspect.u = (u_for_16x9 w, h)[:u]
        @device.safe_area.w             = @device.aspect.u * 16
        @device.safe_area.h             = @device.aspect.u * 9
        @device.safe_area.margin.left   = ((@device.w - @device.safe_area.w).fdiv 2).floor
        @device.safe_area.margin.right  = ((@device.w - @device.safe_area.w).fdiv 2).floor
        @device.safe_area.margin.top    = ((@device.h - @device.safe_area.h).fdiv 2).floor
        @device.safe_area.margin.bottom = ((@device.h - @device.safe_area.h).fdiv 2).floor
        @device.grid_area.outer_gutter  = @device.w / 80
        @device.grid_area.gutter        = @device.w / 160
  
        @device.grid_area.w = @device.safe_area.w - (@device.grid_area.outer_gutter * 2)
        @device.grid_area.h = @device.safe_area.h - (@device.grid_area.outer_gutter * 2)
  
        @device.grid_area.margin.left   = ((@device.w - @device.grid_area.w).fdiv 2).floor
        @device.grid_area.margin.right  = ((@device.w - @device.grid_area.w).fdiv 2).floor
        @device.grid_area.margin.top    = ((@device.h - @device.grid_area.h).fdiv 2).floor
        @device.grid_area.margin.bottom = ((@device.h - @device.grid_area.h).fdiv 2).floor
  
        @device.grid_area.col_count = 24
        @device.grid_area.row_count = 12
        @device.grid_area.cell_w = ((@device.aspect.w - (@device.grid_area.outer_gutter * 2)) - ((@device.grid_area.col_count - 1) * @device.grid_area.gutter)).fdiv @device.grid_area.col_count
        @device.grid_area.cell_h = ((@device.aspect.h - (@device.grid_area.outer_gutter * 2)) - ((@device.grid_area.row_count - 1) * @device.grid_area.gutter)).fdiv @device.grid_area.row_count
  
        @device.control_area.cell_size = @device.grid_area.cell_w
        @device.control_area.cell_size = @device.grid_area.cell_h if @device.grid_area.cell_h < @device.grid_area.cell_w && @device.grid_area.cell_h > 0
        @device.control_area.cell_size = @device.control_area.cell_size.floor
        @device.control_area.w = (@device.control_area.cell_size * @device.grid_area.col_count) + (@device.grid_area.gutter * (@device.grid_area.col_count - 1))
        @device.control_area.h = (@device.control_area.cell_size * @device.grid_area.row_count) + (@device.grid_area.gutter * (@device.grid_area.row_count - 1))
        @device.control_area.margin.left  = (@device.w - @device.control_area.w).fdiv 2
        @device.control_area.margin.right  = (@device.w - @device.control_area.w).fdiv 2
        @device.control_area.margin.top  = (@device.h - @device.control_area.h).fdiv 2
        @device.control_area.margin.bottom  = (@device.h - @device.control_area.h).fdiv 2
        @device
      end
  
      def debug_primitives opts = {}
        @primitives ||= col_count.map_with_index do |col|
                          row_count.map_with_index do |row|
                            cell   = rect row: row, col: col
                            center = Geometry.rect_center_point cell
                            [
                              cell.merge(opts).border,
                              cell.merge(opts)
                                  .label!(x: center.x,
                                          y: center.y,
                                          text: "#{row},#{col}",
                                          size_enum: -3,
                                          vertical_alignment_enum: 1,
                                          alignment_enum: 1)
                            ]
                          end
                        end
                        @primitives
      end
  
      def serialize
        {
          device: @device.serialize,
        }
      end
  
      def inspect
        serialize.to_s
      end
  
      def to_s
        serialize.to_s
      end
  
      def reset
        @primitives = nil
        @rect_cache ||= {}
        @rect_cache.clear
      end
  
    end
  end

#+end_src

*** log.rb
#+begin_src ruby
  # ./dragon/log.rb
  # coding: utf-8
  # Copyright 2019 DragonRuby LLC
  # MIT License
  # log.rb has been released under MIT (*only this file*).
  
  XTERM_COLOR = {
    black:          "\u001b[30m",
    red:            "\u001b[31m",
    green:          "\u001b[32m",
    yellow:         "\u001b[33m",
    blue:           "\u001b[34m",
    magenta:        "\u001b[35m",
    cyan:           "\u001b[36m",
    white:          "\u001b[37m",
    bright_black:   "\u001b[30;1m",
    bright_red:     "\u001b[31;1m",
    bright_green:   "\u001b[32;1m",
    bright_yellow:  "\u001b[33;1m",
    bright_blue:    "\u001b[34;1m",
    bright_magenta: "\u001b[35;1m",
    bright_cyan:    "\u001b[36;1m",
    bright_white:   "\u001b[37;1m",
    reset:          "\u001b[0m",
  }
  
  module GTK
    class Log
      def self.write_to_log_and_puts *args
        return if $gtk.production
        $gtk.append_file_root 'logs/log.txt', args.join("\n") + "\n"
        args.each { |obj| $gtk.log obj, self }
      end
  
      def self.write_to_log_and_print *args
        return if $gtk.production
        $gtk.append_file_root 'logs/log.txt', args.join("\n")
        Object.print(*args)
      end
  
      def self.puts_important *args
        return if $gtk.production
        $gtk.append_file_root 'logs/log.txt', args.join("\n")
        $gtk.notify! "Important notification occurred."
        args.each { |obj| $gtk.log obj }
      end
  
      def self.puts *args
        message_id, message = args
        message ||= message_id
        write_to_log_and_puts message
      end
  
      def self.multiline? *args
        return true if args.length > 1
        return !args[0].to_s.multiline?
      end
  
      def self.join_lines args
        return "" if args.length == 0
        return args if args.is_a? String
        return args[0] if args.length == 1
        return args.to_s.join("\n")
      end
  
      def self.headline name
        @asterisk_count ||= 1
        @asterisk_count = @asterisk_count.greater(1)
        result_from_yield = join_lines yield
        result_from_yield = result_from_yield.each_line.map { |l| "  #{l}" }.join
        r ="#{"*" * @asterisk_count} #{name}\n#{result_from_yield}"
        @asterisk_count -= 1
        @asterisk_count = @asterisk_count.greater(1)
        r
      end
  
      def self.dynamic_block
        "#+BEGIN:
  #{join_lines yield}
  #+END:
  
  "
      end
  
      def self.puts_error *args
        args ||= []
        title = args[0]
        additional = args[1..-1] || []
        additional = "" if additional.length == 0
        if !title.multiline? && join_lines(additional).multiline?
          message = headline "ERROR: #{title}" do
            dynamic_block do
              additional
            end
          end
        elsif title.multiline?
          message = headline "ERROR: " do
            dynamic_block do
              args
            end
          end
        else
          message = "* ERROR: #{title} #{additional}".strip
        end
  
        self.puts message
      end
  
      def self.puts_info *args
        args ||= []
        title = args[0]
        additional = args[1..-1] || []
        additional = "" if additional.length == 0
        if !title.multiline? && join_lines(additional).multiline?
          message = headline "INFO: #{title}" do
            dynamic_block do
              additional
            end
          end
        elsif title.multiline?
          message = headline "INFO: " do
            dynamic_block do
              args
            end
          end
        else
          message = "* INFO: #{title} #{additional}".strip
        end
  
        self.puts message
      end
  
      def self.reset
        @once = {}
        nil
      end
  
      def self.puts_once *ids, message
        id = "#{ids}"
        @once ||= {}
        return if @once[id]
        @once[id] = id
        if !$gtk.cli_arguments[:replay] && !$gtk.cli_arguments[:record]
          $gtk.notify!("Open the DragonRuby Console by pressing [`] [~] [²] [^] [º] or [§]. [Message ID: #{id}].")
        end
        write_to_log_and_puts ""
        write_to_log_and_puts "#{message.strip}"
        write_to_log_and_puts ""
        write_to_log_and_puts "[Message ID: #{id}]"
        write_to_log_and_puts ""
      end
  
      def self.puts_once_info *ids, message
        id = "#{ids}"
        @once ||= {}
        return if @once[id]
        @once[id] = id
        log_info message
      end
  
      def self.print *args
        write_to_log_and_print(*args)
      end
    end
  end
  
  class Object
    def log_print *args
      GTK::Log.print(*args)
    end
  
    def log_important *args
      GTK::Log.puts_important(*args)
    end
  
    def log *args
      GTK::Log.puts(*args)
    end
  
    def log_with_color xterm_escape_code, *args
      log_print xterm_escape_code
      log(*args)
    ensure
      log_reset_color
    end
  
    def log_reset_color
      log_print XTERM_COLOR[:reset]
    end
  
    def log_black *args
      log_with_color XTERM_COLOR[:black], *args
    end
  
    def log_red *args
      log_with_color XTERM_COLOR[:red], *args
    end
  
    def log_green *args
      log_with_color XTERM_COLOR[:green], *args
    end
  
    def log_yellow *args
      log_with_color XTERM_COLOR[:yellow], *args
    end
  
    def log_blue *args
      log_with_color XTERM_COLOR[:blue], *args
    end
  
    def log_magenta *args
      log_with_color XTERM_COLOR[:magenta], *args
    end
  
    def log_cyan *args
      log_with_color XTERM_COLOR[:cyan], *args
    end
  
    def log_white *args
      log_with_color XTERM_COLOR[:white], *args
    end
  
    def log_bright_black *args
      log_with_color XTERM_COLOR[:bright_black], *args
    end
  
    def log_bright_red *args
      log_with_color XTERM_COLOR[:bright_red], *args
    end
  
    def log_bright_green *args
      log_with_color XTERM_COLOR[:bright_green], *args
    end
  
    def log_bright_yellow *args
      log_with_color XTERM_COLOR[:bright_yellow], *args
    end
  
    def log_bright_blue *args
      log_with_color XTERM_COLOR[:bright_blue], *args
    end
  
    def log_bright_magenta *args
      log_with_color XTERM_COLOR[:bright_magenta], *args
    end
  
    def log_bright_cyan *args
      log_with_color XTERM_COLOR[:bright_cyan], *args
    end
  
    def log_bright_white *args
      log_with_color XTERM_COLOR[:bright_white], *args
    end
  
    def log_error *args
      GTK::Log.puts_error(*args)
    end
  
    def log_info *args
      GTK::Log.puts_info(*args)
    end
  
    def log_once *ids, message
      GTK::Log.puts_once(*ids, message)
    end
  
    def log_once_info *ids, message
      GTK::Log.puts_once_info(*ids, message)
    end
  end

#+end_src

*** metadata.rb
#+begin_src ruby
  # ./dragon/metadata.rb
  # coding: utf-8
  # Copyright 2021 DragonRuby LLC
  # MIT License
  # metadata.rb has been released under MIT (*only this file*).
  
  # Contributors outside of DragonRuby who also hold Copyright: Michał Dudziński
  
  module Metadata
    def metadata_file_path
      "metadata/game_metadata.txt"
    end
  
    def get_metadata
      metadata = $gtk.read_file metadata_file_path
  
      if !metadata
        write_blank_metadata
        metadata = $gtk.read_file metadata_file_path
      end
  
      dev_id, dev_title, game_id, game_title, version, icon = *metadata.each_line.to_a
  
      {
        dev_id: dev_id.strip,
        dev_title: dev_title.strip,
        game_id: game_id.strip,
        game_title: game_title.strip,
        version: version.strip,
        icon: icon.strip
      }
    end
  
    def write_blank_metadata
        $gtk.write_file metadata_file_path, <<-S.strip
  #devid=myname
  #devtitle=My Name
  #gameid=mygame
  #gametitle=My Game
  #version=0.1
  #icon=metadata/icon.png
  S
    end
  end

#+end_src

*** numeric.rb
#+begin_src ruby
  # ./dragon/numeric.rb
  # coding: utf-8
  # Copyright 2019 DragonRuby LLC
  # MIT License
  # numeric.rb has been released under MIT (*only this file*).
  
  class Numeric
    include ValueType
    include NumericDeprecated
  
    alias_method :gt,  :>
    alias_method :gte, :>=
    alias_method :lt,  :<
    alias_method :lte, :<=
    alias_method :__original_eq_eq__, :== unless Numeric.instance_methods.include? :__original_eq_eq__
  
    def to_layout_row opts = {}
      $layout.rect(row: self,
                   col: opts.col || 0,
                   w:   opts.w || 0,
                   h:   opts.h || 0).y
    end
  
    def to_layout_col opts = {}
      $layout.rect(row: 0,
                   col: self,
                   w:   opts.w || 0,
                   h:   opts.h || 0).x
    end
  
    def to_layout_w
      $layout.rect(row: 0, col: 0, w: self, h: 1).w
    end
  
    def to_layout_h
      $layout.rect(row: 0, col: 0, w: 1, h: self).h
    end
  
    def to_layout_row_from_bottom opts = {}
      ($layout.row_max_index - self).to_layout_row opts
    end
  
    def to_layout_col_from_right opts = {}
      ($layout.col_max_index - self).to_layout_col opts
    end
  
    # Converts a numeric value representing seconds into frames.
    #
    # @gtk
    def seconds
      self * 60
    end
  
    # Divides the number by `2.0` and returns a `float`.
    #
    # @gtk
    def half
      self / 2.0
    end
  
    def third
      self / 3.0
    end
  
    def quarter
      self / 4.0
    end
  
    def to_byte
      clamp(0, 255).to_i
    end
  
    def clamp *opts
      min = (opts.at 0)
      max = (opts.at 1)
      return min if min && self < min
      return max if max && self > max
      return self
    end
  
    def clamp_wrap min, max
      max, min = min, max if min > max
      return self if self >= min && self <= max
      return min if min == max
      if self < min
        overflow = min - self
        return (max - overflow).clamp_wrap min, max
      end
  
      if self > max
        overflow = self - max
        return (min + overflow).clamp_wrap min, max
      end
  
      return self
    end
  
    def elapsed_time tick_count_override = nil
      (tick_count_override || Kernel.tick_count) - self
    end
  
    def elapsed_time_percent duration
      elapsed_time.percentage_of duration
    end
  
    def new?
      elapsed_time == 0
    end
  
    # Returns `true` if the numeric value has passed a duration/offset number.
    # `Kernel.tick_count` is used to determine if a number represents an elapsed
    # moment in time.
    #
    # @gtk
    def elapsed? offset = 0, tick_count_override = Kernel.tick_count
      (self + offset) < tick_count_override
    end
  
    def frame_index *opts
      frame_count_or_hash, hold_for, repeat, tick_count_override = opts
      if frame_count_or_hash.is_a? Hash
        frame_count         = frame_count_or_hash[:count]
        hold_for            = frame_count_or_hash[:hold_for]
        repeat              = frame_count_or_hash[:repeat]
        tick_count_override = frame_count_or_hash[:tick_count_override]
      else
        frame_count = frame_count_or_hash
      end
  
      tick_count_override ||= Kernel.tick_count
      animation_frame_count = frame_count
      animation_frame_hold_time = hold_for
      animation_length = animation_frame_hold_time * animation_frame_count
      return nil if Kernel.tick_count < self
  
      if !repeat && (self + animation_length) <= (tick_count_override)
        return nil
      else
        return self.elapsed_time(tick_count_override).idiv(animation_frame_hold_time) % animation_frame_count
      end
    rescue Exception => e
      raise <<-S
  * ERROR:
  #{opts}
  #{e}
  S
    end
  
    def zero?
      self == 0
    end
  
    def zero
      0
    end
  
    def one
      1
    end
  
    def two
      2
    end
  
    def five
      5
    end
  
    def ten
      10
    end
  
    alias_method :gt,        :>
    alias_method :above?,    :>
    alias_method :right_of?, :>
  
    alias_method :lt,       :<
    alias_method :below?,   :<
    alias_method :left_of?, :<
  
    def shift_right i
      self + i
    end
  
    def shift_left i
      shift_right(i * -1)
    rescue Exception => e
      raise_immediately e, :shift_left, i
    end
  
    def shift_up i
      self + i
    rescue Exception => e
      raise_immediately e, :shift_up, i
    end
  
    def shift_down i
      shift_up(i * -1)
    rescue Exception => e
      raise_immediately e, :shift_down, i
    end
  
    # This provides a way for a numeric value to be randomized based on a combination
    # of two options: `:sign` and `:ratio`.
    #
    # @gtk
    def randomize *definitions
      result = self
  
      if definitions.include?(:sign)
        result = rand_sign
      end
  
      if definitions.include?(:ratio)
        result = rand * result
      elsif definitions.include?(:int)
        result = (rand result)
      end
  
      result
    end
  
    def rand_sign
      return self * -1 if rand > 0.5
      self
    end
  
    def rand_ratio
      self * rand
    end
  
    def remainder_of_divide n
      mod n
    end
  
    # Easing function progress/percentage for a specific point in time.
    #
    # @gtk
    def ease_extended tick_count_override, duration, default_before, default_after, *definitions
      GTK::Easing.ease_extended self,
                                tick_count_override,
                                self + duration,
                                default_before,
                                default_after,
                                *definitions
    end
  
    # Easing function progress/percentage for a specific point in time.
    #
    # @gtk
    def global_ease duration, *definitions
      ease_extended Kernel.global_tick_count,
                    duration,
                    GTK::Easing.initial_value(*definitions),
                    GTK::Easing.final_value(*definitions),
                    *definitions
    end
  
    # Easing function progress/percentage for a specific point in time.
    #
    # @gtk
    def ease duration, *definitions
      ease_extended Kernel.tick_count,
                    duration,
                    GTK::Easing.initial_value(*definitions),
                    GTK::Easing.final_value(*definitions),
                    *definitions
    end
  
    # Easing function progress/percentage for a specific point in time.
    #
    # @gtk
    def ease_spline_extended tick_count_override, duration, spline
      GTK::Easing.ease_spline_extended self,
                                       tick_count_override,
                                       self + duration,
                                       spline
    end
  
    # Easing function progress/percentage for a specific point in time.
    #
    # @gtk
    def global_ease_spline duration, spline
      ease_spline_extended Kernel.global_tick_count,
                           duration,
                           spline
    end
  
    # Easing function progress/percentage for a specific point in time.
    #
    # @gtk
    def ease_spline duration, spline
      ease_spline_extended Kernel.tick_count,
                           duration,
                           spline
    end
  
    # Converts a number representing an angle in degrees to radians.
    #
    # @gtk
    def to_radians
      self * Math::PI.fdiv(180)
    end
  
    # Converts a number representing an angle in radians to degrees.
    #
    # @gtk
    def to_degrees
      self / Math::PI.fdiv(180)
    end
  
    # Given `self`, a rectangle primitive is returned.
    #
    # @example
    #   5.to_square 100, 300 # returns [100, 300, 5, 5]
    #
    # @gtk
    def to_square x, y, anchor_x = 0.5, anchor_y = nil
      GTK::Geometry.to_square(self, x, y, anchor_x, anchor_y)
    end
  
    # Returns a normal vector for a number that represents an angle in degrees.
    #
    # @gtk
    def vector max_value = 1
      [vector_x(max_value), vector_y(max_value)]
    end
  
    # Returns the y component of a normal vector for a number that represents an angle in degrees.
    #
    # @gtk
    def vector_y max_value = 1
      max_value * Math.sin(self.to_radians)
    end
  
    # Returns the x component of a normal vector for a number that represents an angle in degrees.
    #
    # @gtk
    def vector_x max_value = 1
      max_value * Math.cos(self.to_radians)
    end
  
    def x_vector max_value = 1
      vector_x max_value
    end
  
    def y_vector max_value = 1
      vector_y max_value
    end
  
    def mod n
      self % n
    end
  
    def mod_zero? *ns
      ns.any? { |n| mod(n) == 0 }
    end
  
    def zmod? n
      (self % n) == 0
    end
  
    def multiply n
      self * n
    end
  
    def fmult n
      self * n.to_f
    end
  
    def imult n
      (self * n).to_i
    end
  
    def mult n
      self * n
    end
  
    # @gtk
    def fdiv n
      self / n.to_f
    end
  
    # Divides `self` by a number `n` as a float, and converts it `to_i`.
    #
    # @gtk
    def idiv n
      (self / n.to_f).to_i
    end
  
    # Returns a numeric value that is a quantity `magnitude` closer to
    #`self`. If the distance between `self` and `target` is less than
    #the `magnitude` then `target` is returned.
    #
    # @gtk
    def towards target, magnitude
      return self if self == target
      delta = (self - target).abs
      return target if delta < magnitude
      return self - magnitude if self > target
      return self + magnitude
    end
  
    # Given `self` and a number representing `y` of a grid. This
    # function will return a one dimensional array containing the value
    # yielded by an implicit block.
    #
    # @example
    #   3.map_with_ys 2 do |x, y|
    #     x * y
    #   end
    #   #     x y   x y  x y  x y  x y  x y
    #   #     0*0,  0*1  1*0  1*1  2*0  2*1
    #   # => [  0,    0,   0,   1,   0,   2]
    #
    # @gtk
    def map_with_ys ys, &block
      self.times.flat_map do |x|
        ys.map_with_index do |y|
          yield x, y
        end
      end
    rescue Exception => e
      raise_immediately e, :map_with_ys, [self, ys]
    end
  
    def combinations other_int
      self.numbers.product(other_int.numbers)
    end
  
    def percentage_of n
      (self / n.to_f).cap_min_max(0, 1)
    end
  
    def cap i
      return i if self > i
      self
    end
  
    def cap_min_max min, max
      return min if self < min
      return max if self > max
      self
    end
  
    def lesser other
      return other if other < self
      self
    end
  
    def greater other
      return other if other > self
      self
    end
  
    def subtract i
      self - i
    end
  
    def minus i
      self - i
    end
  
    def add i
      self + i
    end
  
    def plus i
      self + i
    end
  
    def numbers
      (0..self).to_a
    end
  
    # @gtk
    def map
      unless block_given?
        raise <<-S
  * ERROR:
  A block is required for Numeric#map.
  
  S
      end
  
      self.to_i.times.map do
        yield
      end
    end
  
    def each
      unless block_given?
        raise <<-S
  * ERROR:
  A block is required for Numeric#each.
  
  S
      end
  
      self.to_i.times do
        yield
      end
    end
  
    def times_with_index
      unless block_given?
        raise <<-S
  * ERROR:
  A block is required for Numeric#times_with_index.
  
  S
      end
  
      self.to_i.times.with_index do |i|
        yield i
      end
    end
  
    def each_with_index
      unless block_given?
        raise <<-S
  * ERROR:
  A block is required for Numeric#each_with_index.
  
  S
      end
  
      self.to_i.times.with_index do |i|
        yield i
      end
    end
  
    # @gtk
    def map_with_index
      unless block_given?
        raise <<-S
  * ERROR:
  A block is required for Numeric#map.
  
  S
      end
  
      self.to_i.times.map do |i|
        yield i
      end
    end
  
    def __raise_arithmetic_exception__ other, m, e
      raise <<-S
  * ERROR:
  Attempted to invoke :#{m} on #{self} with the right hand argument of:
  
  #{other}
  
  The object above is not a Numeric.
  
  #{e}
  S
    end
  
    def serialize
      self
    end
  
    def self.from_top n
      return 720 - n unless $gtk
      $gtk.args.grid.top - n
    end
  
    def from_top
      Numeric.from_top self
    end
  
    def self.from_right n
      return 1280 - n unless $gtk
      $gtk.args.grid.right - n
    end
  
    def from_right
      Numeric.from_right self
    end
  
    def self.clamp n, min, max
      n.clamp min, max
    end
  
    def mid? l, r
      (between? l, r) || (between? r, l)
    end
  end
  
  class Fixnum
    include ValueType
  
    alias_method :__original_eq_eq__,    :== unless Fixnum.instance_methods.include? :__original_eq_eq__
    alias_method :__original_add__,      :+  unless Fixnum.instance_methods.include? :__original_add__
    alias_method :__original_subtract__, :-  unless Fixnum.instance_methods.include? :__original_subtract__
    alias_method :__original_multiply__, :*  unless Fixnum.instance_methods.include? :__original_multiply__
    alias_method :__original_divide__,   :-  unless Fixnum.instance_methods.include? :__original_divide__
  
    # Returns `true` if the numeric value is evenly divisible by 2.
    #
    # @gtk
    def even?
      return (self % 2) == 0
    end
  
    # Returns `true` if the numeric value is *NOT* evenly divisible by 2.
    #
    # @gtk
    def odd?
      return !even?
    end
  
    # Returns `-1` if the number is less than `0`. `+1` if the number
    # is greater than `0`. Returns `0` if the number is equal to `0`.
    #
    # @gtk
    def sign
      return -1 if self < 0
      return  1 if self > 0
      return  0
    end
  
    # Returns `true` if number is greater than `0`.
    #
    # @gtk
    def pos?
      sign > 0
    end
  
    # Returns `true` if number is less than `0`.
    #
    # @gtk
    def neg?
      sign < 0
    end
  
    def cos
      Math.cos self.to_radians
    end
  
    def cos_r
      Math.cos self
    end
  
    def cos_d
      Math.cos self.to_radians
    end
  
    def sin
      Math.sin self.to_radians
    end
  
    def sin_r
      Math.sin self
    end
  
    def sin_d
      Math.sin self.to_radians
    end
  
    def to_sf
      "%.2f" % self
    end
  
    def ifloor int
      (self.idiv int.to_i) * int.to_i
    end
  end
  
  class Float
    include ValueType
  
    alias_method :__original_add__,      :+ unless Float.instance_methods.include? :__original_add__
    alias_method :__original_subtract__, :- unless Float.instance_methods.include? :__original_subtract__
    alias_method :__original_multiply__, :* unless Float.instance_methods.include? :__original_multiply__
    alias_method :__original_divide__,   :- unless Float.instance_methods.include? :__original_divide__
  
    def serialize
      self
    end
  
    # @gtk
    def sign
      return -1 if self < 0
      return  1 if self > 0
      return  0
    end
  
    def replace_infinity scalar
      return self if !scalar
      return self unless self.infinite?
      return -scalar if self < 0
      return  scalar if self > 0
    end
  
    def to_sf
      "%.2f" % self
    end
  
    def ifloor int
      (self.idiv int.to_i) * int.to_i
    end
  
    def sin
      Math.sin self.to_radians
    end
  
    def cos
      Math.cos self.to_radians
    end
  
    def sin_r
      Math.sin self
    end
  
    def sin_d
      Math.sin self.to_radians
    end
  
    def cos_r
      Math.cos self
    end
  
    def cos_d
      Math.cos self.to_radians
    end
  end
  
  class Integer
    alias_method :__original_round__,    :round  unless Integer.instance_methods.include? :__original_round__
    alias_method :__original_add__,      :+      unless Integer.instance_methods.include? :__original_add__
    alias_method :__original_subtract__, :-      unless Integer.instance_methods.include? :__original_subtract__
    alias_method :__original_multiply__, :*      unless Integer.instance_methods.include? :__original_multiply__
    alias_method :__original_divide__,   :-      unless Integer.instance_methods.include? :__original_divide__
  
    def round *args
      __original_round__
    end
  
    def nan?
      false
    end
  
    def center other
      (self - other).abs.fdiv(2)
    end
  end

#+end_src

*** recording.rb
#+begin_src ruby
  # ./dragon/recording.rb
  # coding: utf-8
  # Copyright 2019 DragonRuby LLC
  # MIT License
  # recording.rb has been released under MIT (*only this file*).
  
  module GTK
    # FIXME: Gross
    # @gtk
    class Replay
      # @gtk
      def self.start file_name = nil
        $recording.start_replay file_name
      end
  
      # @gtk
      def self.stop
        $recording.stop_replay
      end
    end
  
    # @gtk
    class Recording
      def initialize runtime
        @runtime = runtime
        @tick_count = 0
        @global_input_order = 1
      end
  
      def tick
        @tick_count += 1
      end
  
      def start_recording seed_number = nil
        if !seed_number
          log <<-S
  * ERROR:
  To start recording, you must provide an integer value to
  seed random number generation.
  S
          $console.set_command "$recording.start SEED_NUMBER"
          return
        end
  
        if @is_recording
          log <<-S
  * ERROR:
  You are already recording, first cancel (or stop) the current recording.
  S
          $console.set_command "$recording.cancel"
          return
        end
  
        if @is_replaying
          log <<-S
  * ERROR:
  You are currently replaying a recording, first stop the replay.
  S
          return
        end
  
        log_info <<-S
  Recording has begun with RNG seed value set to #{seed_number}.
  To stop recording use stop_recording(filename).
  The recording will stop without saving a file if a filename is nil.
  S
  
        $console.set_command "$recording.stop 'replay.txt'"
        @runtime.__reset__
        @seed_number = seed_number
        @runtime.set_rng seed_number
  
        @tick_count = 0
        @global_input_order = 1
        @is_recording = true
        @input_history = []
        @runtime.notify! "Recording started. When completed, open the console to save it using $recording.stop FILE_NAME (or cancel).", 300
      end
  
      # @gtk
      def start seed_number = nil
        start_recording seed_number
      end
  
      def is_replaying?
        @is_replaying
      end
  
      def is_recording?
        @is_recording
      end
  
      # @gtk
      def stop file_name = nil
        stop_recording file_name
      end
  
      # @gtk
      def cancel
        stop_recording_core
        @runtime.notify! "Recording cancelled."
      end
  
      def stop_recording file_name = nil
        if !file_name
          log <<-S
  * ERROR:
  To please specify a file name when calling:
  $recording.stop FILE_NAME
  
  If you do NOT want to save the recording, call:
  $recording.cancel
  S
          $console.set_command "$recording.stop 'replay.txt'"
          return
        end
  
        if !@is_recording
          log_info "You are not currently recording. Use start_recording(seed_number) to start recording."
          $console.set_command "$recording.start"
          return
        end
  
        if file_name
          text = "replay_version 2.0\n"
          text << "stopped_at #{@tick_count}\n"
          text << "seed #{@seed_number}\n"
          text << "recorded_at #{Time.now.to_s}\n"
          @input_history.each do |items|
            text << "#{items}\n"
          end
          @runtime.write_file file_name, text
          @runtime.write_file 'last_replay.txt', text
          log_info "The recording has been saved successfully at #{file_name}. You can use start_replay(\"#{file_name}\") to replay the recording."
        end
  
        $console.set_command "$replay.start '#{file_name}'"
        stop_recording_core
        @runtime.notify! "Recording saved to #{file_name}. To replay it: $replay.start \"#{file_name}\"."
        log_info "You can run the replay later on startup using: ./dragonruby mygame --replay #{@replay_file_name}"
        nil
      end
  
      def stop_recording_core
        @is_recording = false
        @input_history = nil
        @last_history = nil
        @runtime.__reset__
      end
  
      def start_replay file_name = nil
        if !file_name
          log <<-S
  * ERROR:
  Please provide a file name to $recording.start.
  S
          $console.set_command "$replay.start 'replay.txt'"
          return
        end
  
        text = @runtime.read_file file_name
        return false unless text
  
        if text.each_line.first.strip != "replay_version 2.0"
          raise "The replay file #{file_name} is not compatible with this version of DragonRuby Game Toolkit. Please recreate the replay (sorry)."
        end
  
        @replay_file_name = file_name
  
        $replay_data = { input_history: { } }
        text.each_line do |l|
          if l.strip.length == 0
            next
          elsif l.start_with? 'replay_version'
            next
          elsif l.start_with? 'seed'
            $replay_data[:seed] = l.split(' ').last.to_i
          elsif l.start_with? 'stopped_at'
            $replay_data[:stopped_at] = l.split(' ').last.to_i
          elsif l.start_with? 'recorded_at'
            $replay_data[:recorded_at] = l.split(' ')[1..-1].join(' ')
          elsif l.start_with? '['
            name, value_1, value_2, value_count, id, tick_count = l.strip.gsub('[', '').gsub(']', '').split(',')
            $replay_data[:input_history][tick_count.to_i] ||= []
            $replay_data[:input_history][tick_count.to_i] << {
              id: id.to_i,
              name: name.gsub(':', '').to_sym,
              value_1: value_1.to_f,
              value_2: value_2.to_f,
              value_count: value_count.to_i
            }
          else
            raise "Replay data seems corrupt. I don't know how to parse #{l}."
          end
        end
  
        $replay_data[:input_history].keys.each do |key|
          $replay_data[:input_history][key] = $replay_data[:input_history][key].sort_by {|input| input[:id]}
        end
  
        @runtime.__reset__
        @runtime.set_rng $replay_data[:seed]
        @tick_count = 0
        @is_replaying = true
        log_info "Replay has been started."
        @runtime.notify! "Replay started [#{@replay_file_name}]."
      end
  
      def stop_replay notification_message =  "Replay has been stopped."
        if !is_replaying?
          log <<-S
  * ERROR:
  No replay is currently running. Call $replay.start FILE_NAME to start a replay.
  S
  
          $console.set_command "$replay.start 'replay.txt'"
          return
        end
        log_info notification_message
        @is_replaying = false
        $replay_data = nil
        @tick_count = 0
        @global_input_order = 1
        $console.set_command_silent "$replay.start '#{@replay_file_name}'"
        @runtime.__reset__
        @runtime.notify! notification_message
      end
  
      def record_input_history name, value_1, value_2, value_count, clear_cache = false
        return if @is_replaying
        return unless @is_recording
        @input_history << [name, value_1, value_2, value_count, @global_input_order, @tick_count]
        @global_input_order += 1
      end
  
      def stage_replay_values
        return unless @is_replaying
        return unless $replay_data
  
        if $replay_data[:stopped_at] <= @tick_count
          stop_replay "Replay completed [#{@replay_file_name}]. To rerun, bring up the Console and press enter."
          return
        end
  
        inputs_this_tick = $replay_data[:input_history][@tick_count]
  
        if @tick_count.zmod? 60
          log_info "Replay ends in #{($replay_data[:stopped_at] - @tick_count).idiv 60} second(s)."
        end
  
        return unless inputs_this_tick
        inputs_this_tick.each do |v|
          args = []
          args << v[:value_1] if v[:value_count] >= 1
          args << v[:value_2] if v[:value_count] >= 2
          args << :replay
          $gtk.send v[:name], *args
        end
      end
    end
  end

#+end_src

*** remote_hotload_client.rb
#+begin_src ruby
  # ./dragon/remote_hotload_client.rb
  # coding: utf-8
  # Copyright 2019 DragonRuby LLC
  # MIT License
  # hotload_client.rb has been released under MIT (*only this file*).
  
  module GTK
    class RemoteHotloadClient
      attr :args
  
      def gtk
        args.gtk
      end
  
      def state
        local_state
      end
  
      def initialize local_ip_address
        local_state.local_ip_address = local_ip_address
      end
  
      def tick
        return unless server_available?
        return unless server_needed?
  
        if should_tick? && server_needed? && !local_state.notified
          if server_available?
            remote_log "* REMOTE CLIENT INFO: Hotload server found at #{get_server_ip_address}:9001."
          end
          local_state.notified = true
        end
  
        tick_write_file
        tick_process_file_retrieval
        tick_process_queue
        tick_changes
        tick_http_boot
      end
  
      def should_tick?
        (game_state.tick_count.mod_zero? 60) && game_state.tick_count > 5.seconds
      end
  
      def game_state
        args.state
      end
  
      def local_state
        @local_state ||= OpenEntity.new
        @local_state.hotload_client ||= @local_state.new_entity(:hotload_client,
                                                                notes: "This entity is used by DragonRuby Game Toolkit to provide you hotloading on remote machines.",
                                                                changes: { },
                                                                changes_queue: [],
                                                                write_file_queue: [],
                                                                reloaded_files_times: [])
        @local_state.hotload_client
      end
  
      def remote_log message
        log message
        args.gtk.http_post "http://#{get_server_ip_address}:9001/dragon/log/", { message: "=======\n#{message}\n=======\n" }, ["Content-Type: application/x-www-form-urlencoded"]
      end
  
      def get_server_ip_address
        return local_state.ip_address if local_state.ip_address
        local_state.ip_address ||= ((gtk.read_file 'app/server_ip_address.txt') || "").strip
        local_state.ip_address
      end
  
      def server_available?
        return false if gtk.platform == 'Emscripten'
        get_server_ip_address.length != 0
      end
  
      def server_needed?
        return false if gtk.platform == 'Emscripten'
        local_state.local_ip_address != get_server_ip_address
      end
  
      def tick_changes
        return unless should_tick?
  
        local_state.greatest_tick ||= 0
        local_state.last_greatest_tick ||= 0
  
        tick_http_changes
      end
  
      def tick_http_boot
        return if local_state.booted_at
        local_state.http_boot_debounce ||= 0
        local_state.http_boot_debounce  -= 1
        local_state.http_boot_debounce   = local_state.http_boot_debounce.clamp(0, 120)
        return if local_state.http_boot_debounce > 0
  
        if !local_state.http_boot
          # first retrieve changes.txt which has the following format
          # file with latest change,
          # latest file                              update_time  key
          # tmp/src_backup/src_backup_app_main.rb, 1597926596,  app/main.rb
          local_state.http_boot    = args.gtk.http_get "http://#{get_server_ip_address}:9001/dragon/boot/"
        elsif local_state.http_boot && local_state.http_boot[:http_response_code] == 200
          local_state.last_greatest_tick = local_state.http_boot[:response_data].strip.to_i
          local_state.greatest_tick = local_state.http_boot[:response_data].strip.to_i
          local_state.booted_at = local_state.greatest_tick
          remote_log '* REMOTE CLIENT INFO: HTTP GET for local_state. boot.txt succeeded.'
          remote_log "* REMOTE CLIENT INFO: Looking for changes after: #{local_state.greatest_tick}."
        elsif local_state.http_boot && local_state.http_boot[:http_response_code] == -1 && local_state.http_boot[:complete]
          remote_log '* REMOTE CLIENT INFO: HTTP GET for boot.txt failed. Retrying.'
          local_state.http_boot = nil
          local_state.http_boot_debounce = 120
        end
      end
  
      def tick_http_changes
        return unless local_state.booted_at
  
        if !local_state.http_changes
          local_state.http_changes = args.gtk.http_get "http://#{get_server_ip_address}:9001/dragon/changes/"
        end
  
        if local_state.http_changes && local_state.http_changes[:http_response_code] == 200 && local_state.booted_at
          local_state.last_greatest_tick = local_state.greatest_tick
          # if the retrieval of changes.txt was successful
          local_state.http_changes[:response_data].each_line do |l|
            if l.strip.length != 0
              # within reload state for that specific changes hash
              # set the last time the file was updated
              file_name, updated_at, key = l.strip.split(',')
              file_name.strip!
              updated_at.strip!
              key.strip!
              updated_at = updated_at.to_i
              file_name = file_name.gsub("tmp/src_backup/", "")
  
              # keep an internal clock that denotes that current time on the
              # dev machine
              if updated_at > local_state.greatest_tick
                local_state.greatest_tick = updated_at
  
                # create a new entry in change tracking for the file
                # for every file where the file was last updated, find all the ones where the time is not the same
                # and queue those to be retrieved and required
                # if the last time the dev machine time was retrieved is less than the file time changed
                # then queue the file for reload
                current_updated_at = (local_state.changes[key] || { updated_at: 0 })[:updated_at]
                if updated_at > current_updated_at
                  remote_log "* REMOTE CLIENT INFO: Queueing file #{file_name} for update."
                  local_state.changes[key] = { key: key,
                                               latest_file: file_name,
                                               updated_at: updated_at }
                  local_state.changes_queue << local_state.changes[key]
                end
              end
            end
          end
  
          # set the greatest tick/current time of the machine
          local_state.http_changes = nil
        elsif local_state.http_changes && local_state.http_changes[:http_response_code] == -1 && local_state.http_change[:complete] && local_state.booted_at
          local_state.http_changes = nil
        end
      end
  
      def tick_process_queue
        return if local_state.http_file_changes # don't pop a file off the queue if there is an http request in flight
        return if local_state.processing_file_changes # don't pop a file if there is a file currently being processed
        return unless local_state.changes_queue.length > 0 # return if the queue is empty
  
        # if it isn't empty, pop the first file off the queue (FIFO)
        local_state.processing_file_changes = local_state.changes_queue.shift
  
        # create an http request for the file
        url = "http://#{get_server_ip_address}:9001/dragon/#{local_state.processing_file_changes[:latest_file]}"
        remote_log "* REMOTE CLIENT INFO: Getting new version of #{local_state.processing_file_changes[:latest_file]} (#{url})."
        local_state.http_file_changes = args.gtk.http_get url
      end
  
      def tick_process_file_retrieval
        return if !local_state.http_file_changes
  
        # if the http request has finished successfully
        if local_state.http_file_changes[:http_response_code] == 200
          file_key = local_state.processing_file_changes[:key]
          # notify that a file will be reloaded
          remote_log "* REMOTE CLIENT INFO: Loading #{file_key}: #{local_state.processing_file_changes[:latest_file]}"
          remote_log "#{local_state.http_file_changes[:response_data]}"
  
          # write the latest file with what came back from the response data
          local_state.write_file_queue << { path: file_key, text: local_state.http_file_changes[:response_data] }
  
          # nil out the currently processing file so a new item can be processed from the queue
          # local_state.reloaded_files_times << local_state.processing_file_changes[:key]
          local_state.http_file_changes = nil
          local_state.processing_file_changes = nil
        end
      end
  
      def tick_write_file
        local_state.write_file_queue.each do |h|
          $gtk.write_file h[:path], h[:text]
        end
  
        local_state.write_file_queue.clear
      end
    end
  end

#+end_src

*** runtime/autocomplete.rb
#+begin_src ruby
  # ./dragon/runtime/autocomplete.rb
  # coding: utf-8
  # Copyright 2019 DragonRuby LLC
  # MIT License
  # autocomplete.rb has been released under MIT (*only this file*).
  
  module GTK
    class Runtime
      module Autocomplete
        def autocomplete_parse opts
          if opts[:file] && !opts[:text]
            opts[:text] = read_file opts[:file]
          end
  
          text  = opts[:text]
          index = opts[:index]
          sum   = 0
          lines = text.each_line.to_a.map do |l|
            sum += l.length
            { line: l, length: l.length, sum: sum }
          end
          cursor_line   = lines.find { |l| l[:sum] >= index }
          previous_line = lines.find { |l| l[:sum] < index }
          previous_line ||= { sum: 0 }
          if cursor_line
            sub_index       = index - previous_line[:sum]
            word            = (cursor_line[:line][0..sub_index - 1]).strip
            token           = (word.split " ")[-1]
            dots            = (token.split ".").flat_map { |s| s.split "[" }.flat_map { |s| s.split "]" }.flat_map { |s| s.split "(" }.flat_map { |s| s.split ")" }
            dot             = dots[-1]
          end
  
          {
            text:          opts[:text],
            file:          opts[:file],
            index:         opts[:index],
            cursor_line:   cursor_line,
            previous_line: previous_line,
            word:          word,
            token:         token,
            dots:          dots,
            dot:           dot
          }
        end
  
        def autocomplete_filter_methods keys, *ignores
          ignores ||= []
          ignores   = [ignores].flatten
          keys   = keys.map { |k| k.to_s }
          keys   = keys.reject { |k| k.include? '"' }
                       .reject { |k| k.start_with? "'" }
                       .reject { |k| k.include? "," }
                       .reject { |k| k.start_with? "#" }
          others = ["def", "end"] +
                   [ :entity_keys_by_ref,
                     :entity_name,
                     :as_hash,
                     :clear!,
                     :created_at_elapsed,
                     :entity_id,
                     "entity_id=",
                     "tick_count=",
                     :global_created_at_elapsed,
                     :load_entity_data!,
                     :meta,
                     :meta!,
                     :new?,
                     :old?,
                     :__original_eq_eq__, :set!,
                     :update_entity_keys_by_ref,
                     :with_meta] +
                   ignores + keys.find_all { |k| k.to_s.to_i.to_s == k.to_s }
  
          final = (keys - (others.map { |m| m.to_s })).uniq
          final
        end
  
        def suggest_autocompletion opts
          parse_result = autocomplete_parse opts
          return [] unless parse_result[:cursor_line]
          text  = parse_result[:text]
          word  = parse_result[:word]
          token = parse_result[:token]
          dots  = parse_result[:dots]
          dot   = parse_result[:dot]
  
          return [] if word.strip.start_with? "#"
  
          if word[-1] == "." && token
            lookup = {
              'args'     => lambda { $gtk.args.autocomplete_methods },
              'inputs'   => lambda { $gtk.args.inputs.autocomplete_methods },
              'geometry' => lambda { $gtk.args.geometry.autocomplete_methods },
              'outputs'  => lambda { $gtk.args.outputs.autocomplete_methods },
              'layout'   => lambda { $gtk.args.layouts.autocomplete_methods },
              'keyboard' => lambda { $gtk.args.keyboard.autocomplete_methods },
              'key_down' => lambda { $gtk.args.keyboard.key_down.autocomplete_methods },
              'key_up'   => lambda { $gtk.args.keyboard.key_up.autocomplete_methods },
              'state'    => lambda { $gtk.args.state.autocomplete_methods },
              'fn'       => lambda { $gtk.args.fn.autocomplete_methods },
              '$gtk'     => lambda { $gtk.autocomplete_methods },
              'gtk'      => lambda { $gtk.autocomplete_methods },
              'mouse'    => lambda { $gtk.args.inputs.mouse.autocomplete_methods },
              'click'    => lambda { [:x, :y, :point] }
            }
  
            lookup_result = lookup[dot]
  
            return autocomplete_filter_methods lookup_result.call if lookup_result
  
            if dot[0].upcase == dot[0] && (Object.const_defined? dot.to_sym)
              return (Object.const_get dot.to_sym).autocomplete_methods
            end
  
            start_collecting = false
            dots_after_state = dots.find_all do |s|
              if s == "state"
                start_collecting = true
                false
              else
                start_collecting
              end
            end
  
            target = $gtk.args.state
            dots_after_state.each do |k|
              target = target.as_hash[k.to_sym] if target.respond_to? :as_hash
            end
  
            if target.respond_to? :as_hash
              return autocomplete_filter_methods target.as_hash.keys
            else
              return autocomplete_filter_methods target.autocomplete_methods
            end
          end
  
  
          text = text.each_line.reject { |l| l.strip.start_with? "#" }.join "\n"
          text = text.each_line.map { |l| l.split("#").first }.join "\n"
          text.gsub!("[", " ")
          text.gsub!("]", " ")
          text.gsub!("(", " ")
          text.gsub!(")", " ")
          text.gsub!(":", "")
          text.gsub!(".", " ")
          text.gsub!("=", " ")
          return (autocomplete_filter_methods (text.split " "),
                                              :gtk, :false, :true, :args, :suppress_mailbox, :end)
        end
      end # end Autocomplete
    end # end Runtime
  end # end GTK

#+end_src

*** runtime/benchmark.rb
#+begin_src ruby
  # ./dragon/runtime/benchmark.rb
  # coding: utf-8
  # Copyright 2019 DragonRuby LLC
  # MIT License
  # benchmark.rb has been released under MIT (*only this file*).
  
  module GTK
    class Runtime
      module Benchmark
        def benchmark_single iterations, name, proc
          log <<-S
  ** Invoking :#{name}...
  S
          idx = 0
          r = nil
          time_start = Time.now
          while idx < iterations
            r = proc.call
            idx += 1
          end
          result = (Time.now - time_start).round 3
  
          { name: name,
            time: result,
            time_ms: (result * 1000).to_i }
        end
  
        def benchmark opts = {}
          iterations = opts.iterations
  
          log <<-S
  * BENCHMARK: Started
  ** Caller: #{(caller || []).first}
  ** Iterations: #{iterations}
  S
          procs = opts.find_all { |k, v| v.respond_to? :call }
  
          times = procs.map do |(name, proc)|
            benchmark_single iterations, name, proc
          end.sort_by { |r| r.time }
  
          first_place = times.first
          second_place = times.second || first_place
  
          times = times.map do |candidate|
            average_time = first_place.time
                             .add(candidate.time)
                             .abs
                             .fdiv(2)
  
            difference_percentage = 0
            if average_time == 0
              difference_percentage = 0
            else
              difference_percentage = first_place.time
                                        .subtract(candidate.time)
                                        .abs
                                        .fdiv(average_time)
                                        .imult(100)
            end
  
            difference_time = ((first_place.time - candidate.time) * 1000).round
            candidate.merge(difference_percentage: difference_percentage,
                            difference_time: difference_time)
          end
  
          too_small_to_measure = false
          if (first_place.time + second_place.time) == 0
            too_small_to_measure = true
            difference_percentage = 0
            log <<-S
  * BENCHMARK: Average time for experiments were too small. Increase the number of iterations.
  S
          else
            difference_percentage = (((first_place.time - second_place.time).abs.fdiv((first_place.time + second_place.time).abs.fdiv(2))) * 100).round
          end
  
          difference_time = first_place.time.-(second_place.time).*(1000).abs.round
  
          r = {
            iterations: iterations,
            first_place: first_place,
            second_place: second_place,
            difference_time: difference_time,
            difference_percentage: difference_percentage,
            times: times,
            too_small_to_measure: too_small_to_measure
          }
  
          log_message = []
          only_one_result = first_place.name == second_place.name
  
          if only_one_result
            log <<-S
  * BENCHMARK: #{r.first_place.name} completed in #{r.first_place.time_ms}ms."
  S
          else
            log <<-S
  * BENCHMARK: #{r.message}
  ** Fastest: #{r.first_place.name.inspect}
  ** Second:  #{r.second_place.name.inspect}
  ** Margin:  #{r.difference_percentage}% (#{r.difference_time.abs}ms) #{r.first_place.time_ms}ms vs #{r.second_place.time_ms}ms.
  ** Times:
  #{r.times.map { |t| "*** #{t.name}: #{t.time_ms}ms (#{t.difference_percentage}% #{t.difference_time.abs}ms)." }.join("\n")}
  S
          end
  
          r
        end
      end
    end
  end

#+end_src

*** runtime/draw.rb
#+begin_src ruby
  # ./dragon/runtime/draw.rb
  # coding: utf-8
  # Copyright 2019 DragonRuby LLC
  # MIT License
  # draw.rb has been released under MIT (*only this file*).
  
  module GTK
    class Runtime
      module Draw
        def primitives pass
          if $top_level.respond_to? :primitives_override
            return $top_level.tick_render @args, pass
          end
  
          fn.each_send pass.solids,            self, :draw_solid
          fn.each_send pass.static_solids,     self, :draw_solid
          fn.each_send pass.sprites,           self, :draw_sprite
          fn.each_send pass.static_sprites,    self, :draw_sprite
          fn.each_send pass.primitives,        self, :draw_primitive
          fn.each_send pass.static_primitives, self, :draw_primitive
          fn.each_send pass.labels,            self, :draw_label
          fn.each_send pass.static_labels,     self, :draw_label
          fn.each_send pass.lines,             self, :draw_line
          fn.each_send pass.static_lines,      self, :draw_line
          fn.each_send pass.borders,           self, :draw_border
          fn.each_send pass.static_borders,    self, :draw_border
  
          if !self.production
            fn.each_send pass.debug,           self, :draw_primitive
            fn.each_send pass.static_debug,    self, :draw_primitive
          end
  
          fn.each_send pass.reserved,          self, :draw_primitive
          fn.each_send pass.static_reserved,   self, :draw_primitive
        rescue Exception => e
          pause!
          pretty_print_exception_and_export! e
        end
  
        def draw_solid s
          return unless s
          if s.respond_to? :draw_override
            s.draw_override @ffi_draw
          else
            s = s.as_hash if s.is_a? OpenEntity
            w = s.w
            h = s.h
            if !w && !h
              @ffi_draw.draw_triangle s.x, s.y, s.x2, s.y2, s.x3, s.y3,
                                      s.r, s.g, s.b, s.a,
                                      nil, nil, nil, nil, nil, nil, nil,
                                      (s.blendmode_enum || 1)
            else
              @ffi_draw.draw_solid_2 s.x, s.y, w, h,
                                     s.r, s.g, s.b, s.a,
                                     (s.blendmode_enum || 1)
            end
          end
        rescue Exception => e
          raise_conversion_for_rendering_failed s, e, :solid
        end
  
        def draw_sprite s
          return unless s
          if s.respond_to? :draw_override
            s.draw_override @ffi_draw
          else
            s = s.as_hash if s.is_a? OpenEntity
            w = s.w
            h = s.h
            if !w && !h
              @ffi_draw.draw_triangle s.x, s.y, s.x2, s.y2, s.x3, s.y3,
                                      s.r || 255,
                                      s.g || 255,
                                      s.b || 255,
                                      s.a || 255,
                                      s.path || 'pixel',
                                      s.source_x,
                                      s.source_y,
                                      s.source_x2,
                                      s.source_y2,
                                      s.source_x3,
                                      s.source_y3,
                                      (s.blendmode_enum || 1)
            else
              @ffi_draw.draw_sprite_4 s.x, s.y, w, h,
                                      (s.path || 'pixel').to_s,
                                      s.angle,
                                      s.a, s.r, s.g, s.b,
                                      s.tile_x, s.tile_y, s.tile_w, s.tile_h,
                                      !!s.flip_horizontally, !!s.flip_vertically,
                                      s.angle_anchor_x, s.angle_anchor_y,
                                      s.source_x, s.source_y, s.source_w, s.source_h,
                                      (s.blendmode_enum || 1)
            end
          end
        rescue Exception => e
          raise_conversion_for_rendering_failed s, e, :sprite
        end
  
        def draw_screenshot s
          return unless s
          if s.respond_to? :draw_override
            s.draw_override @ffi_draw
          else
            s = s.as_hash if s.is_a? OpenEntity
            @ffi_draw.draw_screenshot (s.path || '').to_s,
                                      s.x, s.y, s.w, s.h,
                                      s.angle,
                                      s.a, s.r, s.g, s.b,
                                      s.tile_x, s.tile_y, s.tile_w, s.tile_h,
                                      !!s.flip_horizontally, !!s.flip_vertically,
                                      s.angle_anchor_x, s.angle_anchor_y,
                                      s.source_x, s.source_y, s.source_w, s.source_h
          end
        rescue Exception => e
          raise_conversion_for_rendering_failed s, e, :screenshot
        end
  
        def draw_label l
          return unless l
          if l.respond_to? :draw_override
            l.draw_override @ffi_draw
          else
            l = l.as_hash if l.is_a? OpenEntity
            @ffi_draw.draw_label_3 l.x, l.y,
                                   (l.text || '').to_s,
                                   l.size_enum, l.alignment_enum,
                                   l.r, l.g, l.b, l.a,
                                   l.font,
                                   (l.vertical_alignment_enum || 2),
                                   (l.blendmode_enum || 1)
          end
        rescue Exception => e
          raise_conversion_for_rendering_failed l, e, :label
        end
  
        def draw_line l
          return unless l
          if l.respond_to? :draw_override
            l.draw_override @ffi_draw
          else
            l = l.as_hash if l.is_a? OpenEntity
            if l.x2
              @ffi_draw.draw_line_2 l.x, l.y, l.x2, l.y2,
                                    l.r, l.g, l.b, l.a,
                                    (l.blendmode_enum || 1)
            else
              w = l.w || 0
              w = 1 if w == 0
              h = l.h || 0
              h = 1 if h == 0
              @ffi_draw.draw_line_2 l.x, l.y,
                                    l.x + w - 1,
                                    l.y + h - 1,
                                    l.r, l.g, l.b, l.a,
                                    (l.blendmode_enum || 1)
            end
          end
        rescue Exception => e
          raise_conversion_for_rendering_failed l, e, :line
        end
  
        def draw_border s
          return unless s
          if s.respond_to? :draw_override
            s.draw_override @ffi_draw
          else
            s = s.as_hash if s.is_a? OpenEntity
            @ffi_draw.draw_border_2 s.x, s.y, s.w, s.h,
                                    s.r, s.g, s.b, s.a,
                                    (s.blendmode_enum || 1)
          end
        rescue Exception => e
          raise_conversion_for_rendering_failed s, e, :border
        end
  
        def draw_screenshots
          @args.outputs.screenshots.each { |s| draw_screenshot s }
        end
  
        def pixel_arrays
          @args.pixel_arrays.each { |k,v|
            if v.pixels.length == (v.width * v.height)  # !!! FIXME: warning? exception? Different API?
              @ffi_draw.upload_pixel_array k.to_s, v.width.to_i, v.height.to_i, v.pixels
            end
          }
        rescue Exception => e
          pause!
          pretty_print_exception_and_export! e
        end
  
        def draw_primitive p
          return unless p
  
          if p.primitive_marker == :solid
            return draw_solid p
          elsif p.primitive_marker == :sprite
            return draw_sprite p
          elsif p.primitive_marker == :label
            return draw_label p
          elsif p.primitive_marker == :line
            return draw_line p
          elsif p.primitive_marker == :border
            return draw_border p
          else
            raise <<-S
  * ERROR:
  #{p}
  
  I don't know how to use the above #{p.class} with SDL's FFI. Please
  add a method on the object called ~primitive_marker~ that
  returns :solid, :sprite, :label, :line, or :border. If the object
  is a Hash, please add { primitive_marker: :PRIMITIVE_SYMBOL } to the Hash.
  
  S
          end
        end
      end
    end
  end

#+end_src

*** runtime/framerate.rb
#+begin_src ruby
  # ./dragon/runtime/framerate.rb
  # coding: utf-8
  # Copyright 2019 DragonRuby LLC
  # MIT License
  # framerate.rb has been released under MIT (*only this file*).
  
  module GTK
    class Runtime
      module Framerate
        def framerate_init
          @tick_time = Time.new.to_i
        end
  
        def delta_framerate
          (current_framerate || 0) - (@previous_framerate || 0)
        end
  
        def reset_framerate_calculation
          @tick_speed_sum = 0
          @tick_speed_count = 0
          @previous_framerate = 0
        end
  
        def check_framerate
          if @framerate_diagnostics_requested
            log "================================"
            log framerate_get_diagnostics
            @framerate_diagnostics_requested = false
          end
  
          if !@paused
            if @tick_time
              @tick_speed_count += 1
              @tick_speed_sum += Time.now.to_i - @tick_time
              if @tick_speed_count > 60 * 2
                if framerate_below_threshold?
                  @last_framerate = current_framerate
                  if !@console.visible? && !@recording.is_replaying?
                    log framerate_warning_message
                  end
                end
  
                @previous_framerate = current_framerate.floor
              end
            end
  
            @tick_time = Time.new.to_i
          else
            reset_framerate_calculation
          end
        rescue
          reset_framerate_calculation
        end
  
        def framerate_diagnostics
          # request framerate diagnostics to be printed at the end of tick
          @framerate_diagnostics_requested = true
        end
  
        def framerate_below_threshold?
          @last_framerate ||= 60
          current_framerate < @last_framerate &&
            current_framerate < 50 &&
            @previous_framerate > current_framerate &&
            Kernel.tick_count > 600
        end
  
        def current_framerate
          return 60 if !@tick_speed_sum || !@tick_speed_sum
          r = 100.fdiv(@tick_speed_sum.fdiv(@tick_speed_count) * 100)
          if (r.nan? || r.infinite? || r > 58)
            r = 60
          end
          r || 60
        rescue
          60
        end
      end # module Framerate
    end # end class Runtime
  end # end module GTK

#+end_src

*** runtime/framerate_diagnostics.rb
#+begin_src ruby
  # ./dragon/runtime/framerate_diagnostics.rb
  # coding: utf-8
  # Copyright 2019 DragonRuby LLC
  # MIT License
  # framerate_diagnostics.rb has been released under MIT (*only this file*).
  
  module GTK
    class Runtime
      module FramerateDiagnostics
        def framerate_get_diagnostics
          <<-S
  * INFO: Framerate Diagnostics
  You can display these diagnostics using:
  
  #+begin_src
    def tick args
      # ....
  
      # IMPORTANT: Put this at the END of the ~tick~ method.
      args.outputs.debug << args.gtk.framerate_diagnostics_primitives
    end
  #+end_src
  
  ** Draw Calls: ~<<~ Invocation Perf Counter
  Here is how many times ~args.outputs.PRIMITIVE_ARRAY <<~ was called:
  
    #{$perf_counter_outputs_push_count} times invoked.
  
  If the number above is high, consider batching primitives so you can lower the invocation of ~<<~. For example.
  
  Instead of:
  
  #+begin_src
    args.state.enemies.map do |e|
      e.alpha = 128
      args.outputs.sprites << e # <-- ~args.outputs.sprites <<~ is invoked a lot
    end
  #+end_src
  
  Do this:
  
  #+begin_src
    args.outputs.sprites << args.state
                                .enemies
                                .map do |e| # <-- ~args.outputs.sprites <<~ is only invoked once.
      e.alpha = 128
      e
    end
  #+end_src
  
  ** Array Primitives
  ~Primitives~ represented as an ~Array~ (~Tuple~) are great for prototyping, but are not as performant as using a ~Hash~.
  
  Here is the number of ~Array~ primitives that were encountered:
  
    #{$perf_counter_primitive_is_array} Array Primitives.
  
  If the number above is high, consider converting them to hashes. For example.
  
  Instead of:
  
  #+begin_src
    args.outputs.sprites << [0, 0, 100, 100, 'sprites/enemy.png']
  #+begin_end
  
  Do this:
  
  #+begin_src
    args.outputs.sprites << { x: 0,
                              y: 0,
                              w: 100,
                              h: 100,
                              path: 'sprites/enemy.png' }
  #+begin_end
  
  ** Primitive Counts
  Here are the draw counts ordered by lowest to highest z order:
  
  PRIMITIVE   COUNT, STATIC COUNT
  triangles:  #{@args.outputs.triangles.length}, #{@args.outputs.static_triangles.length}
  solids:     #{@args.outputs.solids.length}, #{@args.outputs.static_solids.length}
  sprites:    #{@args.outputs.sprites.length}, #{@args.outputs.static_sprites.length}
  primitives: #{@args.outputs.primitives.length}, #{@args.outputs.static_primitives.length}
  labels:     #{@args.outputs.labels.length}, #{@args.outputs.static_labels.length}
  lines:      #{@args.outputs.lines.length}, #{@args.outputs.static_lines.length}
  borders:    #{@args.outputs.borders.length}, #{@args.outputs.static_borders.length}
  debug:      #{@args.outputs.debug.length}, #{@args.outputs.static_debug.length}
  reserved:   #{@args.outputs.reserved.length}, #{@args.outputs.static_reserved.length}
  
  ** Additional Help
  Come to the DragonRuby Discord channel if you need help troubleshooting performance issues. http://discord.dragonruby.org.
  
  Source code for these diagnostics can be found at: [[https://github.com/dragonruby/dragonruby-game-toolkit-contrib/]]
  S
        end
  
        def framerate_warning_message
          <<-S
  * WARNING:
  Your average framerate dropped below 60 fps for two seconds.
  
  The average FPS was #{current_framerate}.
  
  ** How To Disable Warning
  If this warning is getting annoying put the following in your tick method:
  
  #+begin_src
    args.gtk.log_level = :off
  #+end_src
  
  #{framerate_get_diagnostics}
    S
        end
  
        def current_framerate_primitives
          framerate_diagnostics_primitives
        end
  
        def framerate_diagnostics_primitives
          [
            { x: 0, y: 93.from_top, w: 500, h: 93, a: 128 }.solid!,
            {
              x: 5,
              y: 5.from_top,
              text: "More Info via DragonRuby Console: $gtk.framerate_diagnostics",
              r: 255,
              g: 255,
              b: 255,
              size_enum: -2
            }.label!,
            {
              x: 5,
              y: 20.from_top,
              text: "FPS: %.2f" % args.gtk.current_framerate,
              r: 255,
              g: 255,
              b: 255,
              size_enum: -2
            }.label!,
            {
              x: 5,
              y: 35.from_top,
              text: "Draw Calls: #{$perf_counter_outputs_push_count}",
              r: 255,
              g: 255,
              b: 255,
              size_enum: -2
            }.label!,
            {
              x: 5,
              y: 50.from_top,
              text: "Array Primitives: #{$perf_counter_primitive_is_array}",
              r: 255,
              g: 255,
              b: 255,
              size_enum: -2
            }.label!,
            {
              x: 5,
              y: 65.from_top,
              text: "Mouse: #{@args.inputs.mouse.point}",
              r: 255,
              g: 255,
              b: 255,
              size_enum: -2
            }.label!,
          ]
        end
  
      end
    end
  end

#+end_src

*** runtime/hotload.rb
#+begin_src ruby
  # ./dragon/runtime/hotload.rb
  # coding: utf-8
  # Copyright 2019 DragonRuby LLC
  # MIT License
  # hotlaod.rb has been released under MIT (*only this file*).
  
  module GTK
    class Runtime
      # @visibility private
      module Hotload
        def hotload_init
          @hotload_if_needed = 0
          @mailbox_if_needed = 0
  
          # schema for file_mtimes
          # { FILE_PATH: { current: (Time as Fixnum),
          #                last:    (Time as Fixnum) },
          #   FILE_PATH: { current: (Time as Fixnum),
          #                last:    (Time as Fixnum) } }
          @file_mtimes = { }
  
          @suppress_mailbox = true
          files_to_reload.each { |f| init_mtimes f }
          init_mtimes 'app/mailbox.rb'
        end
  
        def hotload_on_write_file file_name
          return unless file_name.include? 'mailbox.rb'
          @mailbox_if_needed = :force
        end
  
        def files_to_reload
          if @rcb_release_mode
            core_files_to_reload + @required_files
          else
            [
              'dragon/docs.rb',
              'dragon/help.rb',
              'dragon/kernel_docs.rb',
              'dragon/kernel.rb',
              'dragon/easing.rb',
              'dragon/top_level.rb',
              'dragon/log.rb',
              'dragon/geometry.rb',
              'dragon/attr_gtk.rb',
              'dragon/attr_sprite.rb',
              'dragon/object.rb',
              'dragon/class.rb',
              'dragon/string.rb',
              'dragon/entity.rb',
              'dragon/strict_entity.rb',
              'dragon/open_entity.rb',
              'dragon/serialize.rb',
              'dragon/primitive.rb',
              'dragon/nil_class_false_class.rb',
              'dragon/symbol.rb',
              'dragon/numeric_deprecated.rb',
              'dragon/numeric.rb',
              'dragon/hash_deprecated.rb',
              'dragon/hash.rb',
              'dragon/outputs_deprecated.rb',
              'dragon/array_docs.rb',
              'dragon/array.rb',
              'dragon/outputs.rb',
              'dragon/inputs.rb',
              'dragon/mouse_docs.rb',
              'dragon/recording.rb',
              'dragon/grid.rb',
              'dragon/layout.rb',
              'dragon/args_deprecated.rb',
              'dragon/fn.rb',
              'dragon/args.rb',
              'dragon/args_docs.rb',
              'dragon/console_prompt.rb',
              'dragon/console_menu.rb',
              'dragon/console.rb',
              'dragon/assert.rb',
              'dragon/tests.rb',
              'dragon/controller_config.rb',
              'dragon/runtime/draw.rb',
              'dragon/runtime/deprecated.rb',
              'dragon/runtime/framerate.rb',
              'dragon/runtime/c_bridge.rb',
              'dragon/runtime/hotload.rb',
              'dragon/runtime/backup.rb',
              'dragon/runtime/async_require.rb',
              'dragon/runtime/autocomplete.rb',
              'dragon/api.rb',
              'dragon/runtime.rb',
              'dragon/runtime_docs.rb',
              'dragon/trace.rb',
              'dragon/readme_docs.rb',
              'dragon/hotload_client.rb',
              'dragon/wizards.rb',
              'dragon/ios_wizard.rb',
              'dragon/itch_wizard.rb',
            ] + core_files_to_reload + @required_files
          end
        end
  
        def core_files_to_reload
          [
            'repl.rb',
            'app/main.rb',
            'app/repl.rb',
            'app/tests.rb',
            'app/test.rb',
            'app/stdin.rb'
          ]
        end
  
        def init_mtimes file
          @file_mtimes[file] ||= { current: @ffi_file.mtime(file),
                                   last: @ffi_file.mtime(file) }
        end
  
        def hotload_source_files
          @hotload_if_needed += 1
          return unless @hotload_if_needed == 60
          @hotload_if_needed = 0
          files_to_reload.each { |f| reload_if_needed f }
          console.enable
        end
  
        def mailbox_timeout
          if @suppress_mailbox
            60
          else
            3
          end
        end
  
        def check_mailbox
          if @mailbox_if_needed == :force # lol
            reload_if_needed 'app/mailbox.rb', true
            @mailbox_if_needed = 1
            return
          end
          @mailbox_if_needed += 1
          return unless @mailbox_if_needed.mod_zero? mailbox_timeout
          @mailbox_if_needed = 1
          reload_if_needed 'app/mailbox.rb'
        end
  
        def hotload_if_needed
          return if Kernel.tick_count < 0
          hotload_source_files
          check_mailbox
        end
  
        def on_load_succeeded file
          self.files_reloaded << file
          self.reloaded_files << file
          Trace.untrace_classes!
        end
  
        def reset_all_mtimes
          @file_mtimes.each do |file, _|
            @file_mtimes[file].current = @ffi_file.mtime(file)
            @file_mtimes[file].last    = @file_mtimes[file].current
          end
  
          files_to_reload.each do |file, _|
            @file_mtimes[file] ||= {}
            @file_mtimes[file].current = @ffi_file.mtime(file)
            @file_mtimes[file].last    = @file_mtimes[file].current
          end
        end
  
        def reload_if_needed file, force = false
          @file_mtimes[file] ||= { current: @ffi_file.mtime(file), last: @ffi_file.mtime(file) }
          @file_mtimes[file].current = @ffi_file.mtime(file)
          return if !force && @file_mtimes[file].current == @file_mtimes[file].last
          on_load_succeeded file if reload_ruby_file file
          @file_mtimes[file].last = @file_mtimes[file].current
        end
      end
    end
  end

#+end_src

*** string.rb
#+begin_src ruby
  # ./dragon/string.rb
  # coding: utf-8
  # Copyright 2019 DragonRuby LLC
  # MIT License
  # string.rb has been released under MIT (*only this file*).
  
  class String
    include ValueType
  
    def self.wrapped_lines_recur word, rest, length, aggregate
      if word.nil?
        return aggregate
      elsif rest[0].nil?
        aggregate << word + "\n"
        return aggregate
      elsif (word + " " + rest[0]).length > length
        aggregate << word + "\n"
        return wrapped_lines_recur rest[0], rest[1..-1], length, aggregate
      elsif (word + " " + rest[0]).length <= length
        next_word = (word + " " + rest[0])
        return wrapped_lines_recur next_word, rest[1..-1], length, aggregate
      else
        log <<-S
  WARNING:
  #{word} is too long to fit in length of #{length}.
  
  S
        next_word = (word + " " + rest[0])
        return wrapped_lines_recur next_word, rest[1..-1], length, aggregate
      end
    end
  
    def char_byte
      return nil if self.length == 0
      c = self.each_char.first.bytes
      c = c.first if c.is_a? Enumerable
      c
    end
  
    def insert_character_at index, char
      t = each_char.to_a
      t = (t.insert index, char)
      t.join
    end
  
    def excluding_character_at index
      t = each_char.to_a
      t.delete_at index
      t.join
    end
  
    def excluding_last_character
      return "" if self.length <= 1
      return excluding_character_at(self.length - 1)
    end
  
    def end_with_bang?
      self[-1] == "!"
    end
  
    def without_ending_bang
      return self unless end_with_bang?
      self[0..-2]
    end
  
    def self.wrapped_lines string, length
      string.each_line.map do |l|
        l = l.rstrip
        if l.length < length
          l + "\n"
        else
          words = l.split ' '
          wrapped_lines_recur(words[0], words[1..-1], length, []).flatten
        end
      end.flatten
    end
  
    def wrapped_lines length
      String.wrapped_lines self, length
    end
  
    # @gtk
    def wrap length
      wrapped_lines(length).join.rstrip
    end
  
    # @gtk
    def multiline?
      include? "\n"
    end
  
    def indent_lines amount, char = " "
      self.each_line.each_with_index.map do |l, i|
        if i == 0
          l
        else
          char * amount + l
        end
      end.join
    end
  
    def quote
      "\"#{self}\""
    end
  
    def trim
      strip
    end
  
    def trim!
      strip!
    end
  
    def ltrim
      lstrip
    end
  
    def ltrim!
      lstrip!
    end
  
    def rtrim
      rstrip
    end
  
    def rtrim!
      rstrip!
    end
  
    def serialize
      self
    end
  end

#+end_src

*** tests.rb
#+begin_src ruby
  # ./dragon/tests.rb
  # coding: utf-8
  # Copyright 2019 DragonRuby LLC
  # MIT License
  # tests.rb has been released under MIT (*only this file*).
  
  module GTK
    class Tests
      attr_accessor :failed, :passed, :inconclusive
  
      def initialize
        @failed = []
        @passed = []
        @inconclusive = []
      end
  
      def run_test m
        args = Args.new $gtk, nil
        assert = Assert.new
        begin
          log_test_running m
          send(m, args, assert)
          if !assert.assertion_performed
            log_inconclusive m
          else
            log_passed m
          end
        rescue Exception => e
          if test_signature_invalid_exception? e, m
            log_test_signature_incorrect m
          else
            mark_test_failed m, e
          end
        end
      end
  
      def test_methods_focused
        Object.methods.find_all { |m| m.start_with?( "focus_test_") }
      end
  
      def test_methods
        Object.methods.find_all { |m| m.start_with? "test_" }
      end
  
      # @gtk
      def start
        log "* TEST: gtk.test.start has been invoked."
        if test_methods_focused.length != 0
          @is_running = true
          test_methods_focused.each { |m| run_test m }
          print_summary
          @is_running = false
        elsif test_methods.length == 0
          log_no_tests_found
        else
          @is_running = true
          test_methods.each { |m| run_test m }
          print_summary
          @is_running = false
        end
      end
  
      def mark_test_failed m, e
        message = "Failed."
        self.failed << { m: m, e: e }
        log message
      end
  
      def running?
        @is_running
      end
  
      def log_inconclusive m
        self.inconclusive << {m: m}
        log "Inconclusive."
      end
  
      def log_passed m
        self.passed << {m: m}
        log "Passed."
      end
  
      def log_no_tests_found
        log <<-S
  No tests were found. To create a test. Define a method
  that begins with test_. For example:
  #+begin_src
  def test_game_over args, assert
  
  end
  #+end_src
  S
      end
  
      def log_test_running m
        log "** Running: #{m}"
      end
  
      def test_signature_invalid_exception? e, m
        e.to_s.include?(m.to_s) && e.to_s.include?("wrong number of arguments")
      end
  
      def log_test_signature_incorrect m
        log "TEST METHOD INVALID:", <<-S
  I found a test method called :#{m}. But it needs to have
  the following method signature:
  #+begin_src
  def #{m} args, assert
  
  end
  #+end_src
  Please update the method signature to match the code above. If you
  did not intend this to be a test method. Rename the method so it does
  not start with "test_".
  S
      end
  
      def print_summary
        log "** Summary"
        log "*** Passed"
        log "#{self.passed.length} test(s) passed."
        self.passed.each { |h| log "**** :#{h[:m]}" }
        log "*** Inconclusive"
        if self.inconclusive.length > 0
          log_once :assertion_ok_note, <<-S
  NOTE FOR INCONCLUSIVE TESTS: No assertion was performed in the test.
  Add assert.ok! at the end of the test if you are using your own assertions.
  S
        end
        log "#{self.inconclusive.length} test(s) inconclusive."
        self.inconclusive.each { |h| log "**** :#{h[:m]}" }
        log "*** Failed"
        log "#{self.failed.length} test(s) failed."
        self.failed.each do |h|
          log "**** Test name: :#{h[:m]}"
          log "#{h[:e].to_s.gsub("* ERROR:", "").strip}\n#{h[:e].__backtrace_to_org__}"
        end
      end
    end
  end

#+end_src

*** trace.rb
#+begin_src ruby
  # ./dragon/trace.rb
  # coding: utf-8
  # Copyright 2019 DragonRuby LLC
  # MIT License
  # trace.rb has been released under MIT (*only this file*).
  
  # Contributors outside of DragonRuby who also hold Copyright:
  # - Dan Healy: https://github.com/danhealy
  
  module GTK
    module Trace
      IGNORED_METHODS = [
        :define_singleton_method, :raise_immediately, :instance_of?,
        :raise_with_caller, :initialize_copy, :class_defined?,
        :instance_variable_get, :format, :purge_class, :instance_variable_defined?,
        :metadata_object_id, :instance_variable_set, :__printstr__,
        :instance_variables, :is_a?, :p, :kind_of?, :==, :log_once,
        :protected_methods, :log_once_info, :private_methods, :open,
        :!=, :initialize, :object_id, :Hash, :methods, :tick, :!,
        :respond_to?, :yield_self, :send, :instance_eval, :then,
        :__method__, :__send__, :log_print, :dig, :itself, :log_info,
        :remove_instance_variable, :raise, :public_methods, :instance_exec,
        :gets, :local_variables, :tap, :__id__, :class, :singleton_class,
        :block_given?, :_inspect, :puts, :global_variables, :getc, :iterator?,
        :hash, :to_enum, :printf, :frozen?, :print, :original_puts,
        :srand, :freeze, :rand, :extend, :eql?, :equal?, :sprintf, :clone,
        :dup, :to_s, :primitive_determined?, :inspect, :primitive?, :help,
        :__object_methods__, :proc, :__custom_object_methods__, :Float, :enum_for,
        :__supports_ivars__?, :nil?, :fast_rand, :or, :and,
        :__caller_without_noise__, :__gtk_ruby_string_contains_source_file_path__?,
        :__pretty_print_exception__, :__gtk_ruby_source_files__,
        :String, :log, :Array, :putsc, :Integer, :===, :here,
        :raise_error_with_kind_of_okay_message, :better_instance_information,
        :lambda, :fail, :method_missing, :__case_eqq, :caller,
        :raise_method_missing_better_error, :require, :singleton_methods,
        :!~, :loop, :numeric_or_default, :`, :state, :inputs, :outputs, "args=".to_sym,
        :grid, :gtk, :dragon, :args, :passes, :tick, :grep_source, :grep_source_file,
        :numeric_or_default, :f_or_default, :s_or_default, :i_or_default,
        :comment, :primitive_marker, :xrepl, :repl
      ]
  
      def self.traced_classes
        @traced_classes ||= []
        @traced_classes
      end
  
      def self.mark_class_as_traced! klass
        @traced_classes << klass
      end
  
      def self.untrace_classes!
        traced_classes.each do |klass|
          klass.class_eval do
            all_methods = klass.instance_methods false
            if klass.instance_methods.respond_to?(:__trace_call_depth__)
              undef_method :__trace_call_depth__
            end
  
            GTK::Trace.filter_methods_to_trace(all_methods).each do |m|
              original_method_name = m
              trace_method_name = GTK::Trace.trace_method_name_for m
              if klass.instance_methods.include? trace_method_name
                alias_method m, trace_method_name
              end
            end
          end
        end
        $last_method_traced = nil
        @traced_classes.clear
        $trace_enabled = false
        if !$gtk.production
          $gtk.write_file_root 'logs/trace.txt', "Add trace!(SOMEOBJECT) to the top of ~tick~ and this file will be populated with invocation information.\n"
        end
      end
  
      def self.trace_method_name_for m
        "__trace_original_#{m}__".to_sym
      end
  
      def self.original_method_name_for m
        return m unless m.to_s.start_with?("__trace_original_") && m.to_s.end_with?("__")
        m[16..-3]
      end
  
      def self.filter_methods_to_trace methods
        methods.reject { |m| m.start_with? "__trace_" }.reject { |m| IGNORED_METHODS.include? m }
      end
  
      def self.trace_times_string
        str = []
        $trace_performance.sort_by {|method_name, times| -times[:avg] }.each do |method_name, times|
          str << "#{method_name}: #{times[:sum].round(2)}/#{times[:count]} #{times[:min]}ms min, #{times[:avg].round(2)}ms avg, #{times[:max]}ms max"
        end
        str.join("\n")
      end
  
      def self.flush_trace pad_with_newline = false
        $trace_puts ||= []
        puts "(Trace info flushed!)"
        if $trace_puts.length > 0
          text = $trace_puts.join("").strip + "\n" + self.trace_times_string + "\n"
          if pad_with_newline
            $gtk.append_file_root 'logs/trace.txt', "\n" + text.strip
          else
            $gtk.append_file_root 'logs/trace.txt', text.strip
          end
        end
        $trace_puts.clear
      end
  
      # @gtk
      def self.trace! instance = nil
        $trace_history ||= []
        $trace_enabled = true
        $trace_call_depth ||=0
        $trace_performance = Hash.new {|h,k|
          h[k] = {
            min:   100000,
            max:   0,
            avg:   0,
            sum:   0,
            count: 0
          }
        }
        flush_trace
        instance = $top_level unless instance
        return if Trace.traced_classes.include? instance.class
        all_methods = instance.class.instance_methods false
        instance.class.class_eval do
          attr_accessor :__trace_call_depth__ unless instance.class.instance_methods.include?(:__trace_call_depth__)
          GTK::Trace.filter_methods_to_trace(all_methods).each do |m|
            original_method_name = m
            trace_method_name = GTK::Trace.trace_method_name_for m
            alias_method trace_method_name, m
            $trace_puts << "Tracing #{m} on #{instance.class}.\n"
            define_method(m) do |*args|
              instance.__trace_call_depth__ ||= 0
              tab_width = " " * (instance.__trace_call_depth__ * 8)
              instance.__trace_call_depth__ += 1
              $trace_call_depth = instance.__trace_call_depth__
              parameters = "#{args}"[1..-2]
  
              $trace_puts << "\n  #{tab_width}#{m}(#{parameters})"
  
              execution_time = Time.new
  
              $last_method_traced = trace_method_name
              $trace_history << [m, parameters]
  
              result = send(trace_method_name, *args)
  
              class_m = "#{instance.class}##{m}"
              completion_time = ((Time.new - execution_time).to_f * 1000).round(2)
              $trace_performance[class_m][:min] = [$trace_performance[class_m][:min], completion_time].min
              $trace_performance[class_m][:max] = [$trace_performance[class_m][:max], completion_time].max
              $trace_performance[class_m][:count] += 1
              $trace_performance[class_m][:sum] += completion_time
              $trace_performance[class_m][:avg] = $trace_performance[class_m][:sum].fdiv($trace_performance[class_m][:count])
  
              instance.__trace_call_depth__ -= 1
              instance.__trace_call_depth__ = instance.__trace_call_depth__.greater 0
              $trace_puts << "\n #{tab_width} #{completion_time > 10 ? '!!! ' : ''}#{completion_time}ms success: #{m}"
              if instance.__trace_call_depth__ == 0
                $trace_puts << "\n"
                $trace_history.clear
              end
              result
            rescue Exception => e
              instance.__trace_call_depth__ -= 1
              instance.__trace_call_depth__ = instance.__trace_call_depth__.greater 0
              $trace_puts << "\n #{tab_width} failed: #{m}"
              if instance.__trace_call_depth__ == 0
                $trace_puts << "\n #{tab_width}         #{e}"
                $trace_puts << "\n"
              end
              $trace_call_depth = 0
              GTK::Trace.flush_trace true
              raise e
            end
          end
        end
        mark_class_as_traced! instance.class
      end
    end
  end

#+end_src

*** tweetcart.rb
#+begin_src ruby
  # ./dragon/tweetcart.rb
  # coding: utf-8
  # Copyright 2019 DragonRuby LLC
  # MIT License
  # tweetcart.rb has been released under MIT (*only this file*).
  
  def $top_level.TICK &block
    $top_level.define_method(:tick) do |args|
      args.outputs[:scene].w = 160
      args.outputs[:scene].h = 90
      args.outputs[:scene].background_color = [0, 0, 0, 0]
      block.call args
      args.outputs.sprites << { x: 0, y: 0, w: 1280, h: 720, path: :scene }
    end
  
    def $top_level.no_clear! render_target_name
      $args.outputs[:render_target_name].clear_before_render = false
    end
  
    def $top_level.bg! *rgb
      r,g,b = rgb
      r ||= 255
      g ||= r
      b ||= g
      $args.outputs.background_color = [r, g, b]
    end
  
    def $top_level.slds
      $args.outputs[:scene].sprites
    end
  
    def $top_level.slds! *os
      if (os.first.is_a? Numeric)
        sld!(*os)
      else
        os.each { |o| sld!(*o) }
      end
    end
  
    def $top_level.sld! *params
      x, y, w, h, r, g, b, a = nil
      if params.length == 2
        x, y = params
      elsif params.length == 3 && (params.last.is_a? Array)
        x = params[0]
        y = params[1]
        r, g, b, a = params[2]
        r ||= 255
        g ||= r
        b ||= g
        a ||= 255
      elsif params.length == 4
        x, y, w, h = params
      elsif params.length == 5 && (params.last.is_a? Array)
        x = params[0]
        y = params[1]
        w = params[2]
        h = params[3]
        r,g,b,a = params[4]
        r ||= 255
        g ||= r
        b ||= g
        a ||= 255
      elsif params.length >= 7
        x, y, w, h, r, g, b = params
      else
        raise "I don't know how to render #{params} with reasonable defaults."
      end
  
      w ||= 1
      h ||= 1
      r ||= 255
      g ||= 255
      b ||= 255
      a ||= 255
  
      slds << { x: x, y: y,
                w: w, h: h,
                r: r, g: g, b: b, a: a,
                path: :pixel }
    end
  
    def $top_level.sin_r radians
      Math.sin radians
    end
  
    def $top_level.cos_r radians
      Math.cos radians
    end
  
    def $top_level.sin degrees
      Math.sin degrees.to_radians
    end
  
    def $top_level.cos degrees
      Math.cos degrees.to_radians
    end
  
    def $top_level.sin_d degrees
      Math.sin degrees.to_radians
    end
  
    def $top_level.cos_d degrees
      Math.cos degrees.to_radians
    end
  end
  
  =begin
  wht  = [255] * 3
  red  = [255, 0, 0]
  blu  = [0, 130, 255]
  purp = [150, 80, 255]
  
  TICK {
    bg! 0
  
    slds << [0, 0, 3, 3, 0, 255, 0, 255]
  
    sld!     10, 10
    sld!     20, 20, 3, 2
    sld!     30, 30, 2, 2, red
    sld!     35, 35, blu
  
    slds!    40, 40
  
    slds!   [50, 50],
            [60, 60, purp],
            [70, 70, 10, 10, wht],
            [80, 80, 4, 4, 255, 0, 255]
  }
  =end

#+end_src

*** wizards.rb
#+begin_src ruby
  # ./dragon/wizards.rb
  # coding: utf-8
  # Copyright 2019 DragonRuby LLC
  # MIT License
  # wizards.rb has been released under MIT (*only this file*).
  
  class Wizard
    def metadata_file_path
      "metadata/game_metadata.txt"
    end
  
    def get_metadata
      metadata = $gtk.read_file metadata_file_path
  
      if !metadata
        write_blank_metadata
        metadata = $gtk.read_file metadata_file_path
      end
  
      dev_id, dev_title, game_id, game_title, version, icon = *metadata.each_line.to_a
  
      {
        dev_id:     dev_id.strip.gsub("#", "").gsub("devid=", ""),
        dev_title:  dev_title.strip.gsub("#", "").gsub("devtitle=", ""),
        game_id:    game_id.strip.gsub("#", "").gsub("gameid=", ""),
        game_title: game_title.strip.gsub("#", "").gsub("gametitle=", ""),
        version:    version.strip.gsub("#", "").gsub("version=", ""),
        icon:       icon.strip.gsub("#", "").gsub("icon=", "")
      }
    end
  end
  
  class WizardException < Exception
    attr_accessor :console_primitives
  
    def initialize *console_primitives
      @console_primitives = console_primitives
    end
  end
  
  module GTK
    class Wizards
      attr_accessor :ios, :itch
  
      def initialize
        @ios = IOSWizard.new
        @itch = ItchWizard.new
      end
    end
  end

#+end_src

