Xoo is an abstract board game for 2-3 players, played on a 19x19 square grid. Xoo was created by Steven Metzger in 2009.

Players take turns placing stones of their own color and, periodically, stones from a neutral set - the player who connects four stones (orthogonally or diagonally) of their color OR the neutral color is the winner.


Xoo is played on a traditional goban, shown below.


The board starts with an "X" on the center intersection.

Each player alternates placing stones of their own color, starting with black. However, starting on black's second turn and white's third turn, a player must place an "X" on the board instead of a piece of their own color every three turns.

A player wins when they make a line of four stones of their own color OR four "X's" on their turn:


Three-player Xoo: The third player takes a set of light blue stones as their own. The goal remains the same, but players only place an "X" on every fourth turn (and blue starts placing X's on their fourth turn)