Impossible cube ambiguity present in a Necker cube illustration, in which a cube is drawn with its edges as line segments, and can be interpreted as being in either of two different three-dimensional orientations. An impossible cube is usually rendered as a Necker cube in which the line segments representing the edges have been replaced by what are apparently solid beams. In Escher's print, the top four joints of the cube, and the upper of the two crossings between its beams, match one of the two interpretations of the Necker cube, while the bottom four joints and the bottom crossing match the
Cube 2: Sauerbraten episodic gameplay and deathmatches on multiplayer maps with AI bots instead of human opponents. Cube 2: Sauerbraten started as a redesign of the original "Cube" game engine. The "Cube 2: Sauerbraten" engine is written in C++ and OpenGL. "Cube 2: Sauerbraten" shares most of its design goals and philosophy with its predecessor, but using a new 6-directional heightfield (or octree) world model. Its first, developer-only, release was made on February 27, 2004. One of the latest releases, dubbed the "Justice Edition", debuted on July 19, 2010, adding two new player models, thirty new user-created maps, several new game modes, including