That music is fire! I loved that soundtrack as well as the art! My only critique which is really something optional is that if you expand on this game, I think only requiring a set number of monkeys instead of all of them could open itself up to some interesting levels. Also, some more visual guides to show what button does what. I still really like the game and still can't get over how nice that music is!
Edit: I forgot to add that the difficulty curve is very well done!