Really solid idea and interesting gameplay mechanics! I like the music a lot too. It seemed very tricky at first, but once I learned how to "fly" by flipping gravity back and forth, I was able to get through some stuff much more easily. It was rough only being able to move in one direction, but a really cool limitation! As others have said, the time rewind didn't really seem to add anything to the game. I almost found it more annoying to have to rewind myself back several times out of a spike pit, than it would have been to just start over from a checkpoint. Really great game though, I like it!