Some of us were born before the international marketing phenomenon of Ernő Rubik’s bűvös kocka, circa 1980. For those (like myself) who were actively collecting puzzles, it was an exciting time. (It had been 100 years since Noyes Chapman’s Fifteen Puzzle craze.)

It is possible to scramble Rubik’s Cube into any one of 43252003274489856000 different states, yet — through the memorization of some simple procedures — almost anyone can restore (in a hundred moves, or so) the cube to its initial condition: My best time was around four minutes.

It was known that there exist some scrambled states of the cube that require at least 20 moves (face turns) to get to — hence, those states require at least 20 moves to unscramble. Are there configurations that require more moves? No one knows.*

A few months ago, the best answer was that 26 moves suffice to unscramble any scrambled cube. Then, in March, Tom Rokicki showed that 25 moves was already sufficient. By May, Rokicki (granted idle time on Sony Pictures Imageworks render-farm computers) reduced that number to 23. One might expect even further progress in the near future, but the road all the way down to 20 will not be easy!

Of the several dozen cube variants in my collection, the picture shows part of a Braille Rubik’s Cube. Of course, the existence of unsymmetric puncture marks on the faces skews the mathematics of both the number of possible states and the number of moves necessary to unscramble them — assuming that we expect the unsymmetric punctures (2 and 3) to align on their respective (yellow and red) completed faces.

*Addendum: Problem solved!