Pull Request now includes Tetris!

completed: warmups
tower of Hanoi (with saving via YAML)
Mastermind(no saving, but yes AI)

Single block Tetris, with high scores saved, plus a difficulty setting as well. (Boring under about level 8).
One small tweak would be to align the hash symbols when rendering to the screen.  So you could do something like:
print number <=9 ? "#{number}\: " : #{number}\:" (extra space on the single digit numbers)