Go (Baduk)

Setup

• Two players, a board and a supply of black and white stones. The board starts empty.
• This site starts on the full-size 19×19 board used in tournaments. A game takes about an hour (faster against the CPU). Choose 9×9 for a quick game or practice, or 13×13 in between; the computer plays all three sizes.
• Stones go on the intersections (points), not inside the squares. Black plays first.
• White receives 6.5 points of komi as compensation for moving second. The half point means the game cannot end in a tie.

How to play

• Players take turns placing one stone of their colour on any empty point. A stone never moves once placed; it only leaves the board if it is captured.
• Stones of one colour that touch along the lines (not diagonally) form a group. The empty points next to a group are its liberties.
• When a group loses its last liberty, it is captured and removed, and the stones are kept as prisoners. A group with only one liberty left is said to be in atari.
• Suicide is not allowed: you may not play a stone that leaves your own group with no liberties — unless the same move captures, which gives it liberties again.
• Ko: you may not immediately recapture a single stone if that would bring back the position from before your opponent's move. Play elsewhere first (a ko threat); on your next turn the recapture is legal.
• Instead of placing a stone, you may pass.
• You can enable ring marks for stones in atari in settings (off by default). A □ marks the point you cannot retake because of ko.

Winning

• When both players pass in a row, play stops.
• You then agree which stones on the board are dead: press them to mark them, and press Confirm on both sides. If you cannot agree, press Back to play and settle it on the board.
• This site uses territory scoring (Japanese rules): count the empty points surrounded by your stones alone, add your prisoners and the dead stones taken off your opponent's territory, and give White 6.5 komi. The higher total wins.
• Empty points in seki touch both colours and count for nobody. Either player may give up at any time.

House rules