In one of my classes our teacher told us about this, and its actually pretty fun. The point is to get the red object that starts in the blue area into the red area completly. Its good physics, and the solutions can be shared, so I thought it would be a good idea to post. I don't pay for it, but if you do you get to make your own level. Its pretty fun I guess, passes time.
http://fantasticcontraption.com/
http://fantasticcontraption.com/