Nicely polished game. You have got a nice concept going, and apart from a tiny bug at level 3, where my size got reset before the end of the level it all worked great.
In my opinion the difficulty starts way too low and scaled very quickly. Level 3 was not a challenge at all, whereas 4 was completely impossible. I also would've preffered the rotation to be controlled by the mouse, so you can do that much quicker. Maybe even full mouse control would work, anything to speed up the speed at which you can react.
Sadly as a result of my skill issue I didnt get far enough in the boss level to see if there was anything special. Overall well done though, I really like the concept.