Press Space to do a short jump. You can jump infinitely, but if you touch the top of the screen of the bottom of the screen you lose. Kinda like flappy bird, but your jumps are bigger.
@griffpatch's platformer tutorial helped me make gravity. Anything else is 100% mine!!! (God's not in the credits because I'm a certified atheist. Please don't throw a buzzsaw-shaped angel halo at me.)