So, you can solve the Rubik's Cube, good for you, but what about the Square One? Erno Rubik is nothing compared to Karel Hršel and Vojtech Kopský, who invented the Square One puzzle, also called by its full title, "Back to Square One", or its shorter name of "Cube 21". It's shaped like a Rubik's Cube, but it's cut like a freak show, adding that layer of difficulty that challenges you.