Echochrome is a puzzle game that involves a mannequin figure traversing a rotatable world where physics and reality depend on perspective. The world is occupied by Oscar Reutersvärd's impossible constructions. Echochrome requires the player to control a moving character to visit, in any order, particular locations on the surfaces of collections of three-dimensional shapes. Scoring is simply a matter of timing completion of each level.
Source: Wikipedia, "Echochrome," available under the CC-BY-SA License.