Algodoo

Just press PLAY then sit back and enjoy watching these colorful critters act crazy. I guess you can use this as a screen saver.

Oh, by the way, if after a while they start to get lazy and don't move around much, just grab 'em with your cursor and toss them around. They will get their energy back!

Oh, by the way (again) these critters don't move with thrusters or any weird script. All I did was to set edgeblur value to vel(1) (which is the Y or vertical velocity). I discovered when I do that it causes their strange movements, and I don't know why.