Well, I was really into formalizing stuff when I was in college, you know proving that a cryptographic algorithm was correct by formalizing them as black boxes talking to each other, that sort of thing. Then I just started thinking about how to formalize mechanical things. One of the very things I remember is coming to the conclusion that all motions of a machine can be implemented as a combination of linear and rotational motions (and that's where the two things that move on mockmechanics, the track and the wagon, come from), but I don't know if that is true. But I don't really have any prior art, I had a 2d version that didn't work years ago but I think I lost it.