I liked the way you could scale up and down and grant differen"powers", and it makes sense since you're a pufferfish, clever and well done.
The mechanics themselves could be more polished, the controller felt a bit awkward when flying, and the game design itself made it pointless to "puffer up" as I won without ever enlarging. (several ways to fix that, and you are almost on the money in the beginning, the answer is more boxes that the small fish can't get through) and just generally, the level designing was poor and needs more attention.
The music and general audio-feedback was good, made it feel more like a game. Well done for submitting! :)