Most, well all the games/scenarios I've seen so far on Greenfoot are with a plain surface.
I was wondering if there is a way to let the character move when the surface looks like that
<iframe src="https://docs.google.com/file/d/0B9cdcVQ0KaTZbWVYZlV0R3VSQms/preview" width="640" height="480"></iframe>
(other than creating thousands of classes)

Thanks for the scenario, it actually is exactly what I was thinking of. Great :)