The board and the stones

Two players take turns placing stones on the empty intersections of the grid — Black moves first. Once placed, a stone never moves; it can only be captured and removed. Instead of placing a stone you may always pass.

Liberties and capture

The empty points directly next to a stone (up, down, left, right) are its liberties. Stones of the same color standing next to each other form a group and share their liberties. When a group's last liberty is filled by the opponent, the whole group is captured and taken off the board.

Two forbidden moves: suicide and ko

Suicide: you may not place a stone that leaves its own group with zero liberties — unless that move captures enemy stones first, which frees up liberties.

Ko: after your stone is captured in a one-for-one exchange, you may not recapture immediately — that would repeat the position forever. Play somewhere else first; next turn the recapture is allowed again.

Life, death, and eyes

A group that surrounds two separate empty points — two eyes — can never be captured: the opponent would have to fill both eyes at once, and playing inside either one alone is suicide. Making groups that can form two eyes, and preventing your opponent's groups from doing so, is the heart of the game.

Ending the game and scoring

When both players pass in succession, the game ends. This page uses area scoring: your score is the number of empty points only your stones surround (your territory) plus the number of your stones on the board. White receives 7.5 extra points (komi) as compensation for moving second — the half point also rules out ties. The higher total wins. Here the final score is estimated by the neural net.

Tips for your first games

Start on the 7×7 or 9×9 board — full 19×19 games are long and disorienting at first. Corners are the easiest territory to hold, then the sides; the center is hardest. Don't try to rescue every stone: sacrificing a stone or two to build a strong wall is often the better trade. Stay out of atari, and use the Undo button freely — watching how KataGo punishes a move is the fastest way to learn.