This is the 3D printer killer app that I want... (Score 1)

I have 3-year-old twin girls, and what I want is a way to easily create Rube Goldberg devices which will help my girls understand basic physics. I want a kit I can print with levers, pulleys, inclined planes, windmills, catapults, springs, and more, that my girls can add to and just go nuts with. When this exists and is easy, believe me, there are a LOT of parents out there who will buy one for their kids.