I would like a draw button, or maybe a draw button that appears if there hasn't been any damage for N rounds. (Or a forced draw if there hasn't been any damage done in N rounds.)
Also I like the increasing chance idea, I'm both annoyed at me not getting any cards, and jealous with people who get them practically every other game ~.~
I like the game. If you like this, you'll love Syoban Action, it's probably the inspiration for this game, standalone, and slightly better imho (and has harder puzzles).
Great game overall! Minor annoyances:
Overall volume is too loud.
The voice and loud background menu in the menus you have to click through often can get annoying.
I don't like all the songs :P
No badges.
Too addicting ;)
But on the whole, great game!