This is progressing very nicely :) What other sorts of paint options do you expect to add? (And might i add that i LOVE the color picker)

Um java itself is not a virus, and if thats what you believe, why did you install it on your computer? My source won't harm you either, its just text files and class files, if you don't want to run it on greenfoot, you could always just look at the text files with notepad. (and C:\ is not a folder, its your disk :P)

You could download the source if you wanted to take a closer look ;) Basically I didn't erase the screen every frame before redrawing it, i only erased a little bit of it, so that on each frame parts of the previous frames showed through. Note that this only works when you are NOT using actors :P

OMG its a Troll!!!!! *runs*

Yeah, most likely the best thing to do would be to rewrite the engine completely using momentum and torque rather than deformation and springs. The way the physics is calculated right now is very hacky x.x

Because friction is not fully implemented during collisions. It IS implemented however wrong, which is why the blocks don't slide around a lot though.