Nice art style and music. :) No sound fx though. :(
There is a nice variety of levels and obstacles, and the gameplay feels responsive. I also agree with what somebody said before me; the level length is perfect for how hard the levels get later on.
All in all there are a few unfair sections, and the collision detection against walls feels a little iffy.
I think level 4 is my most loved/hated one. I really like the obstacles on the right, but not the bullet hell on the left. ;) And the second to last level is really hard...
Great game. :D