Variations of Rubik's Cubes (L-R: Rubik's Revenge, Rubik's Cube, Professor's Cube, and Pocket Cube)
Rubik's Cube or (informally) Rubix Cube is a mechanical puzzle invented in 1974 by the Hungarian sculptor and professor of architecture Ernő Rubik. The plasticcube comes in four widely available versions: the 2×2×2 ("Pocket Cube"), the 3×3×3 standard cube, the 4×4×4 ("Rubik's Revenge"), 5×5×5 ("Professor's Cube"). 6×6×6 and 7×7×7 cubes are currently being produced. The 3×3×3 version, which is the version usually meant by the term "Rubik's Cube," has nine square faces on each side, for a total area of fifty-four faces, and occupies the volume of twenty-six unit cubes (not counting the invisible cube in the center). Typically, the faces of the Cube are covered by stickers in six solid colors, one for each side of the Cube. When the puzzle is solved, each side of the Cube is a solid color. The original 3×3×3 version celebrated its twenty-fifth anniversary in 2005, when a special edition Cube in a presentation box was released, featuring a sticker in the centre of the white face (which was replaced with a reflective surface) with a "Rubik's Cube 1980-2005" logo.
