This game was a lot of fun to play. I liked leveling up with the powers. The enemies came in really fast at the end, though. But it was broken up into waves which is nice. 

The presentation is really good, I loved the art (especially the intro) and the music was good too. As for criticism, I would say the I wish the changing of elements was mapped to another button as the mouse wheel is somewhat obtuse to use (at least for me). Also the gameplay turned out to be a bit monotonous after a while. Great work and keep making games!