The rules are simple! There are two squares in the box, the more a square bounces, the more speed it will gain, when squares collide, the square with the highest velocity will deal damage to the other, and slow down whilst the other continues to have its speed. I'm working on "Events" to change the shape of the game, so do with that what you will.

(PS. If there's no second square, please just start a new game, I have no idea why that happens.)