Square One (puzzle)
The Square One, also known as Back to Square One and Cube 21, is a puzzle similar to the Rubik's Cube. Its distinguishing feature among the numerous Rubik's Cube variants is that it can change shape as it is twisted, due to the way it is cut, thus adding an extra level of challenge and difficulty. The Super Square One and Square Two puzzles have been recently introduced. The Super Square One has two additional layers that can be scrambled and solved independently of the rest of the puzzle, and the Square Two has extra cuts made to the top and bottom layer, making the edge and corner wedges the same size.
History
The Square One, with the full name "Back to Square One", and alternative name "Cube 21", was invented by Karel Hršel and Vojtěch Kopský around 1990. Application for Czechoslovak patent was filed on 8 November 1990, the patent was approved on 26 October 1992 with patent number CS 277266 B6. On March 16, 1993, it was patented in the USA with patent number US5,193,809. Its design was also patented on October 5, 1993, with patent number D340,093.
