This was such a nice, polished, and complete experience I really don't have much to add, and I don't want to seem nitpicky, but I do have some feedback. The game does get too easy after a couple of upgrades. I didn't continue getting them, but the enemies quickly stopped becoming a problem after the homing and extra projectile upgrades. Also, a confirm button on the upgrade would help me, who was in such a flow state trying to get to the next level I bought an upgrade I didn't need. Finally, I would find the character controller more responsive if I could feel my character crouch in mid-air. I felt myself missing the visual feedback of an in-air crouch of Mirrors Edge, for example. Here's a video of it if you haven't played.
The really cool, dark/mage-y art style, and great level design with very consistent pacing, some difficult jumps, and hard enemies (at least until the power spike) made for a great experience! I could play a lot more of this.