Dots and Boxes

Dots and Boxes is a pencil-and-paper game for two players.
Starting with an empty grid of dots, two players take turns adding a single horizontal or vertical line between two unjoined adjacent dots.
The player who completes the fourth side of a 1×1 box earns one point and takes another turn.
The game ends when no more lines can be placed.
The winner is the player with the most points.