Skewb

The Skewb (/ˈskjuːb/) is a combination puzzle and a mechanical puzzle in the style of Rubik's Cube. It was invented by Tony Durham and marketed by Uwe Mèffert. Although it is cubical in shape, it differs from Rubik's construction in that its axes of rotation pass through the corners of the cube rather than the centres of the faces. There are four such axes, one for each space diagonal of the cube. As a result, it is a deep-cut puzzle in which each twist affects all six faces.

Mèffert's original name for this puzzle was the Pyraminx Cube, to emphasize that it was part of a series including his first tetrahedral puzzle Pyraminx. The catchier name Skewb was coined by Douglas Hofstadter in his Metamagical Themas column, and Mèffert liked it enough not only to market the Pyraminx Cube under this name but also to name some of his other puzzles after it, such as the Skewb Diamond.

Higher order Skewbs, named Master Skewb and Elite Skewb, have also been made.

Although the Skewb looks simple, its pieces are actually divided into subgroups and have restrictions that are apparent upon examining the puzzle's mechanism. The 8 corners are split into two groups—the four corners attached to the central 4-armed spider and the four "floating" corners that can be removed from the mechanism easily. These corners cannot be interchanged i.e. in a single group of four corners, their relative positions are unchanged. They can be distinguished by applying pressure on the corner—if it squishes down a bit, it's a floating corner. The centers only have two possible orientations—this becomes apparent by either scrambling a Skewb-alike puzzle where the center orientation is visible (such as the Skewb Diamond or Skewb Ultimate), or by disassembling the puzzle.

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Wikipedia