Tricky puzzle or learning tool?

Fantastic Contraption is part puzzle part learning experience. You are given a limited set of materials (Tinkertoy wheels and connectors) and the simple goal of move one block across the screen. By the end of the series of puzzles, the solver has developed an intuitive feel for torque and elasticity as well as invented many of the common structures known to engineering.

http://www.kongregate.com/games/inXile_Ent/fantastic-contraption

Even if you decide not to play, you may want to scan youtube to see the wide range of machines and solutions that other players used.