via http://pdroms.de/

I Wanna Flip The Sky by Tom is a platformer along the lines of I Wanna Be The Guy or Battle Kid. In each level you’re trying to reach the exit door while avoiding traps like spikes and conveyor belts. The trick is you can flip gravity a limited number of times each level.

http://forums.nesdev.com/viewtopic.php?f=22&t=9218