The game is played starting with a rectangular array of dots.
The two players take turns to join two adjacent dots with a horizontal or vertical line. If a player completes the fourth side of a box they initial that box and must draw another line.
When all the boxes have been completed the winner is the player who has initialled the most boxes.
The game is more complex than it initially appears, and even on a 7x7 grid there is plenty of opportunity for skilful play.