Well, I can't give this game a low score, because there really is nothing wrong with it. All the games function fine, the only problem being that there's no menu option once you start a pong game, so if you want to quit, you have to close the whole game. I can't give this game a high score either, though, because there really is nothing special about it. You basically just replaced regular keys with the scroll button. Overall, it's okay, no more, no less. 5/10.
By the way, there's a bit of a glitch in Pong where if you hit the ball at the wrong angle, it get's stuck in your paddle. It doesn't happen too often, but you may want to look into it.