Awesome
I love this kind of game, and I really enjoyed this one. The effects are nice, the music fitting and the enemies fun and varied. One design issue I noticed is that enemies seem to level up with you, which makes for a very interesting meta-game but also undermines that part of the game.
When I played, I did everything I could to actually avoid the pixels! I often opted not to go for a powerup because there were too many pixels in the way. Also, the "more pixels"-powerup seems pretty silly since it will speed up the increase in difficulty, but not power you up. If the difficulty increase was timer-based, I would probably enjoy this game even more, as I actually like to level. :)