@Dragonfree +1 I am part of a RigidChips forum and thank you for recommending this game. It's actually a physics simulator with simple physics and is a sandbox, you also get to create your own models and can pick other people's models up from http://rigidchips.forum-motion.com/
@madbob2 I think that RigidChips is one of the best games of all time. We used to play it in the computer room at school, but it got blocked by the teachers :/ Powder Toy hasn't been blocked because it's open source, and if they blocked it, I'd make a new version...