Dots and Boxes

Dots and Boxes is a pencil-and-paper game published by French mathematician Édouard Lucas in 1889 as 'La Pipopipette'. Starting from a grid of dots, two players take turns drawing a single horizontal or vertical line between adjacent dots. A player who completes the fourth side of a 1×1 box marks it and gets an extra turn. Winner has the most boxes. Combinatorial-game theory reveals surprising depth — the endgame is dominated by long-chain analysis and the 'double-cross' strategy.