In the fall of 2009, I took a course offered as a collaboration between Stanford and the Exploratorium. We studied exhibit design, user engagement, and education through play. Each student designed and realized an exhibit that illustrated a specific concept or phenomenon. The class culminated in a show at the Exploratorium followed by a show on Stanford campus.
Since high school, I've been fascinated by the Reuleaux triangle. It's a curve of constant width, which means - among other things - that it can "roll" as smoothly as a circle on a flat surface. To demonstrate this, I designed and built a planetary gear setup with interchangeable gears. Some are circular, and some are Reuleaux triangles, but both revolve at the same speed. By allowing direct interaction with the piece, users can see for themselves that there is no "trick" - just an interesting geometric surprise.