What a great idea! I liked the Style and the Music fits nicely.
Gameplay-wise there are a lot of things you can do with this concept. I really liked the fact that you can use your mass to push/destroy things and to "squeeze through" some tight obstacles.
On the negative side, I didn't like the platforming so much and I had trouble jumping onto platforms/obstacles. In my opinion the game should focus more on puzzles than on platforming. Furthermore, I think the game should give the player more time and room to play around and learn before they are able to tackle more difficult segments!
All in all, great game idea!!!