The game was well done. I think the graphics and the difficulty was alright, but I wouldn't really call it original (I see a /lot/ of similarities with Time Fcuk and others, esp. the gravity thing). The idea was great, though :D I also hated the part where the controls get a bit sh*tty when the gravity is shifted (unless you really intended for that), but it does add to the rage factor.
All in all, great game, nicely done. 3 stars :D