Outstanding game!
I love the interactivity of this game. Everything about its playability is absolutely awesome. I'd say the graphics are pretty sub-par, but at least the game doesn't use all my CPU because of it, and honestly, the look of the thing is perfectly fine.
The only real complaint I have is the lack of checkpoints, a pause button, and above all, there needs to be more than just one life per play... but it's your game. Just a suggestion on my part.
Overall, I really enjoyed the hell out of this and will definately be playing it off and on for quite a while I think. Good job!