oh. u cant see it at all, except for when it bounces and barely in the middle, u should make it so its color is like blinking as it moves or something easier to see so its not completely invisible. but its a great game ::)

Very cool. But when going against the AI, the invisible ball power-up doesn't really help you against them cause they know where it is regardless. In multiplayer, that'd be awesome!

I don't know, I like it on the sides because that way you can use two fingers easily instead of moving one finger back and forth. But I will probably add an option for it.

You could allow all four keys 'w', 'a', 's', and 'd' active for the one player and all four of the arrow keys active for the other player. Just use something like [code]if (Greenfoot.isKeyDown("w") || Greenfoot.isKeyDown("a"))[/code]for each combination of keys (I am not sure if those two particular keys are a matching combination of keys; I was just trying to show the code format here).