Laggy
I like the concept, the graphics are spectacular, and I think the game is pretty innovative, but the levels get progressively slower as time goes on, and it eventually becomes pretty much unplayable. I'm not sure why that is; might have something to do with the particles causing a long-term slowdown, because it doesn't look like there's too much more on the screen in later levels; at least, not enough to cause that great of a slowdown. But it's definitely the one thing I'd try to fix.