This PC game has likely been mentioned, but DD7 and I adore the old PC game from Sierra called Return of the Incredible Machine: Contraptions. You can see it in action here:

It runs fine on Windows 7 and I like it more than the more recent Crazy Machines because the parts are easier to see and in general it is just more fun and creative.

The puzzles are very challenging and educational thanks to its terrific simulated physics. It teaches problem solving as you are forced to learn cause and effect and understand the functions and limitations of each part, yet you can also be creative and solve them in simpler or wilder ways. You can also challenge yourself by trying to solve a given contraption in one go, thinking many steps ahead.

Finally there is a sandbox mode where you can build your own contraptions.

I believe you can buy the entire series repackaged on for only $9.99 or you can find originals on eBay.

Last edited by Pru; 04/13/11 11:39 AM. Reason: purchase info