Check out the “edge-matching” puzzle pictured above. The setup of this game consists of seven contiguous hexagons arranged inside a circle. The edge of each hexagon is assigned a number from 1 to 6. The goal of this game is to match the numbers on the various edges of the hexagons without lifting any of the hexagons from the circle (i.e., by rotating the hexagons within the circle). According to this summary of the game by bohus, there is only one solution, and “there’s no rational way to build to an answer. All you can do with [this game] is keep trying to find the fit. There’s no logical solve to find. I even consulted a mathematician. A child has about as much of a chance solving this time-waster.” You can print out your own version of this puzzle here. (Hat tip: the excellent Cliff Pickover, via Twitter.)