Join Five

Join Five (also known as Morpion solitaire, Cross 'n' Lines or Line Game) is a paper and pencil game for one or two players, played on a plus-shaped grid of dots. The origins of the game are probably in northern Europe. References to the game first appeared in French publications in the 1970s. In addition to being played recreationally, the game has been the subject of theoretical studies and computer searches for solutions.