This demonstration displays curves of constant width—planar curves that maintain the same width and height when rotated. When curves of constant width are rolled as wheels of a bicycle, they provide a uniform ride as long as the rider is supported by the top of each wheel rather than by the center, as in traditional bicycles. This demonstration, contributed by Robert Young, traces the locations of two points on the back wheel and the center of the back wheel over time. https://wolfr.am/RsojM2ZW