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.
Go variants
Alak is a Go-like game restricted to a single spatial dimension.
Go can be extended to three dimensions. One example is Diamond Go, which uses the structure of a carbon diamond crystal lattice. With many such Go variants, the nature of the game changes dramatically the standard 4-connectivity of the points is changed, however, Diamond Go maintains this connectivity. Another example is Margo, by Cameron Browne, a variant played with marbles that can be stacked on top of one another.