Go (game)
Two players, "Black" and "White", take turns placing a "stone" (game piece) of their own color on a vacant "point" (intersection) of the grid on a Go board. Black plays first. If there is a large difference in skill between the players, the weaker player typically uses Black and is allowed to place two or more stones on the board to compensate for the difference (see Go handicaps). The official grid comprises 19×19 lines, though the rules can be applied to any grid size. 13×13 and 9×9 boards are popular choices to teach beginners, or for playing quick games. Once placed, a stone may not be moved to a different point.
Irensei
There are two restrictions on this: (1) A line of seven stones which covers any point on the outer two lines of the board is not a win, and (2) Black cannot make a line of eight or more stones. However, when a group of stones is enclosed by the enemy as by the Go rules, the stones are removed (remember that diagonal is not considered a connection for capturing but is considered a connection for a win). Also, the suicide and Ko rules apply, and indeed are often crucial in winning the game.