How did a Soviet researcher's hobby become the best-selling video game ever?

It spread like a virus, first for free and then through a tangle of Cold War deals. In the mid-1980s Alexey Pajitnov, a speech recognition and artificial intelligence researcher at a Soviet Academy of Sciences computing centre in Moscow, wrote Tetris in his spare time in about three weeks. Floppy disk copies passed from hand to hand around Moscow and into Eastern Europe, and from there Western companies scrambled for the rights.

The idea came from a puzzle. Pajitnov had bought a set of pentominoes, shapes made of five squares, and played with it in his office. On the computer he simplified it to tetrominoes, pieces of four squares, because there are only seven of them instead of twelve. His machine, the Elektronika 60, had no graphics, so the first pieces were drawn with spaces and brackets. The name joins "tetra", four, with his favourite sport, tennis.

The game was so gripping that a Soviet psychologist noticed his colleagues' research suffering because they kept playing it. But Pajitnov could not profit: under Soviet rules a state agency controlled software exports, and he had given his computing centre the rights for ten years. One Western dealer even sold a licence for Tetris before he owned it. In America the game was marketed as the first Soviet product sold in North America.

The breakthrough was Nintendo's Game Boy, which came with Tetris in the United States; many people bought the console just to play it. Tetris has since sold 520 million copies, according to its company, and Pajitnov finally began to benefit only in 1996, when he co-founded The Tetris Company.