[Coda]

I've done some heavy-duty code cleanup. It shouldn't really make a difference to performance (it might actually perform slightly worse but not enough to actually notice), but the code is nicer now.

I also added a Pause button -- press escape. It'll also automatically pause the game if it lags too much, because this probably means you left the window.

And then I also added high score persistence -- if you're in a browser that supports it, it'll remember your high score across pageviews.