todo
- confirm quit / new game prompts
- message box / set_message methods
- error messages for invalid moves
- column labels
- directions screen first
- recognition when game is over
- draw 3 functionality (bigger change)
- score?
- timer?
- locally saved stats?
- auto win (when all cards are face up)?
- scrolling so max column size doesn't force huge screen
- ongoing: clean up duplicated code
- arrow pad navigation support? (might make column moves more intuitive)