TODO:
* Make "set" button visually interesting when 3 cards selected
* Make "how to play" fit on smaller screen resolution.
  * I think scrolling makes the most sense... unfortunately
* Make background scale with window
* Scale cards with window resolution
  * Genuinely not sure how to do this...

Later:
* Make button(s) look pretty
* for testing, hotkeys h and enter for help and submit respectively