Has anyone here heard of incredibots 2? I tried it out a few months ago and I enjoyed it a lot. Incredibots 2 is a free online physics sandbox where you can build pretty much anything. Among my builds that I have made are an arcade claw machine(didn't save D:), a rocket car, an antigravity car, numerous tanks, and few walker mechs. Incredibots 2 is free, and doesn't take a long time to learn how to play. Visit
http://incredibots2.com/ to play the game. You need to sign up to save your robots. Search my Incredibots username (Kodak97) to see my bots.