Almost really good. The graphics are sharp as hell, the music is catchy, and the gameplay is tight. There are some major issues with gameplay though. First, I really don't like how you have to use the spacebar to take back a move. Implementing the scroll wheel as an optional alternative might have been a nice way to make sure the game maintained a mouse-only control scheme.
I think different modes might also have been a nice idea. The time limits were really daunting to me and made me feel uncomfortable about experimentation, especially with such a unique game as this. The bonuses that you collect were a nice way to mix things up, but I wasn't able to get a very clear view of how many there were in a level, and that was also kind of discouraging.
Anyway, I feel like this game would have been really fun if you'd had some kind of racing mode, collecting mode, puzzle mode, etc. instead of one linear campaign that seems to assume everyone is comfortable with the control scheme before they are.