swish.mp3
https://www.freesound.org/people/qubodup/sounds/60030/
Creative Commons 0 License: https://creativecommons.org/publicdomain/zero/1.0/

select.mp3
http://www.freesound.org/people/GameAudio/sounds/220173/
Creative Commons 0 License: https://creativecommons.org/publicdomain/zero/1.0/

upgrade.mp3
http://www.freesound.org/people/GameAudio/sounds/220184/
Creative Commons 0 License: https://creativecommons.org/publicdomain/zero/1.0/

click.mp3
http://www.freesound.org/people/GameAudio/sounds/220178/
Creative Commons 0 License: https://creativecommons.org/publicdomain/zero/1.0/
