Punchball v0.4: Rip janky bumpers

At long last, I finally modified the bumpers to make them actually bump you accurately. This was (un)surprisingly difficult, and I also made it so you can exit the game at any time.

Why I skipped 0.3 is because I want to have it be 0.5 when it just needs a nice coat of paint, and all that's missing from the core concept is sound effects. I now realize that it may have not been the best idea, but it's too late.