Revamped Surface Physics, Added Windows Support

After receiving some great feedback on physics behaviors in the game, I took the much-needed leap to revamp the surface physics. This resulted not only in a significant performance boost, but in a more accurate/predictable physics reaction with the surfaces in the game. Here's a "level" I threw together to test the bounce physics:

I also added the option to download the game for Windows. WebGL is unfortunately somewhat limited in copy-pasting, and that's a vital component of the online/social aspects of the game. It's frustrating to have to manually type in (or out) a level code.

I've overdue for adding the first non-player entity, so my next effort will likely be adding a spawner for squashable enemies. I also hope to have a conveyor-belt-style surface available in the level maker pretty soon!