Minus Cube Minus Cube The Minus Cube () is a 3D mechanical variant of the n-puzzle which was manufactured in the Soviet Union. It consists of a bonded transparent plastic box containing seven small cubes, each glued together from two U-shape parts: one white and one coloured. The length of one side of the interior of the box is slightly more than twice the length of the side of a small cube. There is an empty space the size of one small cube inside the box and the small cubes are moveable inside the box by tilting the box causing a cube
Square-1 (puzzle) shapes are possible for the middle layer, there is a quick sequence of twists which changes the shape of the middle layer from one to the other without touching the rest of the puzzle. Once the puzzle has a cube shape, the upper and lower layers are cut in an Iron Cross-like fashion, or equivalently cut by two concentric (standard) crosses, that make an angle with each other. Like Rubik's Cube, the pieces are colored. For the puzzle to be solved, not only does it need to be in cube shape, but each face of the cube must also have