Oh wait, I know what the problem is. Just hit ENTER when you're in the main menu. I must have messed something up in the UI by trying to give it gamepad support. If using a gamepad, just press the south button, otherwise press ENTER to start the game
Last thing, WebGL gamepad is kind of buggy and it inverts the Y axis. So, even when it's in line with the jam theme, I recommend using keyboard when playing in the browser
