Incredibots gives you the tools to buld an almost infinite variety of machines (or robots) that you then use to solve puzzles. This is by far the most sophisticated game of it's type that I have seen. It takes a little time and effort to learn how to build the machines, but the flexibility is amazing once you get the hang of it.
There is some similarity to the crayon physics games, but you have much more precise control of the shapes you draw and more options. You can build on screen machines to do quite a variety of tasks.
At this writing the game is still in beta testing, but I have not found any bugs and it seems to be very stable and complete.
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