There’s a lot more to Tetris that you probably think. ON A cold February day in the 1970s, 15-year-old Alexey Pajitnov leapt over a pile of snow in Moscow. As he landed, his leg hit the pavement with “a sickening crack”. Soviet doctors put him in a full leg cast, requiring two to three months of in-home convalescence. To help him cope with boredom,...