I know you guys love these things so I can't wait to see some of your replays (id suggest not viewing my replays until you play a few levels that way you build your contraptions based on your interpretation of physics rule sets instead of someone elses): http://fantasticcontraption.com/
PS: Once you get into this game you may lose a lot of time that day.
http://FantasticContraption.com/?designId=742354 - There's my mission to mars
http://FantasticContraption.com/?designId=744362 - my big ball