Ah cool gameplay! Fun fun fun! Thanks for posting it!
It might be nice to be able to skip the high-score entry screen if you want to try again. It takes too long I think after dying to play again. (the fastest way to start again is to turn the arduboy off+on )
Also, holding down a cursor key on the keyboard screen should move several tiles if you hold for long enough, I think.
99 seconds is a long time for a timer - maybe something that recharges that you can use for at most 4 or 5 seconds (say) might work better?
edit: I've played a bit more - what makes things slow at the start is that you are prompted to enter in a high score for at least the first five games (probably more!) - if the high score table had some starting values built in that might fix that problem.