Sandro del Prete
New Figure: The Impossible Ring Disk with Two Sides and Two Edges
This new shape, though different from the one above it, has the same qualities as the other figures. An object would travel a full cycle along its path in a clockwise direction - and once again in a counterclockwise direction - without passing over the other objects on the ring disk. The object moves toward the observer or in the opposite direction, away from the observer, but this to-and-fro motion illusory. It relies on a temporal element, and could therefore be called four-dimensional.