Just to make it clear, this scenario isn't functional here on the gallery: It's intended to be downloaded and played around with in Greenfoot. (Right wjm?)

That looks interesting. Can you explain a little about the pattern it generates? (I know the source is available, it would be nice to have a little explanation here though).

One minor bug, if you keep the mouse cursor over one of the buttons when it is green and keep clicking, it will not turn red when the last background is reached (until you move the cursor off the button and then back onto it).