TODO:
* for testing, hotkeys h and enter for help and submit respectively
* there is a "new game" bug where I think SetNumber is not cleaned up properly
* new game should work
* A deck with face-down card(s)
* Make "set" button visually interesting when 3 cards selected
* Better shuffling

Later:
* View all cards with some indication of in-set
* Make button(s) look pretty