Press "Space" to change gravity. When you hit the bottom or the top, you automatically change gravity. This game is somewhat complex, may not work on older browsers or slower computers. I have cut it down significantly, but could still lag your device.
Many people have helped me with this project. First of all, I would like to thank @silac6, better known as the creator of Ninja Run. You inspired me to create this game. You also gave me the concept of pushing the player back until they hit the edge. Your script also gave me ideas of how to do things if I didn't know how myself. I also copied your music. I would also like to thank Jet Pack Joyride, you gave me the idea of changing gravity.