-Great sprites
-Great form-switching... but add more diversity between some of them.
-Some of the sounds when you collect something (when wearing earphones) are way too loud and high pitched, and they hurt my poor sensitive ears. That's normally enough to make me quit playing a game.
-Henshin animation is very cool, albeit a bit too long.
Overall I had fun. It still feels like it needs some work, but once the little details are added (and the music) I think it's going to be something to remember. Good job!