This is neat…. a sphericon is a 3-dimensional geometric solid with a single continuous face and two edges (sort of like a MÃ¶bius strip). The sphericon rolls along a wobbley path but ends up traveling in a straight line!
Over at Fold Play, someone turned a pie into a sphericon – watch as it rolls in a straight line down the slope. Pretty neat.
They also have templates to make your own sphericon pie.