This game seems to just be missing a lot. There's no audio, the player fires absurdly fast (disrupting the balance of the entire game), and the enemies don't really do anything except charge straight into the brain. I like the concept of building defenses around the brain; I think you did a nice job with that. Also, I would suggest changing the controls so that the mouse wheel changes between items, because that would make it much faster to get out of a pinch. You have a good concept here, but you just fell a little short. Nonetheless, good job, and keep making games!