Invented in the 1970s by a Hungarian professor of design, Erno Rubik, the toy that was sold in the United States as the Rubik's Cube became a popular phenomenon in the early 1980s. The Rubik's Cube was the most challenging — and for many people, infuriating — puzzle ever to achieve mass-market success. Composed of twenty-six smaller cubes, or "cubies," the cube presented nine colored squares on each of its six faces. When the cube was purchased, each face was of a uniform color, different from that of any of the other faces; after the faces were rotated randomly, the cube would end up a jumble of colors — and most people had no idea how to restore it to its original state. People spent hours, if not days, rearranging the cube in dozens of the 43,252,003,274,489,855,999 (43 quintillion) positions other than the one correct position before achieving success or giving up...