Go rules and how to play: from 9×9 to 19×19 boards

Go modes

• Random match (ランダムマッチ): play online against someone who chose the same board size
• Room match (ルーム対戦): play a friend using a room ID
• Play against the CPU (CPU対戦): four strength levels, with hints and undo
• Two players (ふたりで対局): take turns on one device

Basic rules of Go

• Black and White take turns placing one stone on an intersection. Black plays first.
• A stone never moves once placed. If you fill all the liberties (adjacent empty points) of a group of your opponent's stones, you capture it.
• You cannot play where your own stones would be captured immediately (a suicide point), unless the move captures your opponent's stones.
• You cannot immediately recapture in a way that brings the board back to the previous shape (ko).
• You can pass, and the game ends when both players pass in a row. Dead stones are removed and added to the prisoners, and the players compare territory plus prisoners. White gets 6.5 points of komi.

How to play on Asobi Lounge

• Click the intersection where you want to play. On a phone, tap once to check the spot, then tap the same point again to play.
• When the game ends, dead stones are judged automatically and shown faded. If a judgment is wrong, tap a stone to switch it between dead and alive, and the breakdown of territory and prisoners is shown.
• An online game ends when both players agree on the count, or when someone resigns. If there are still moves to play, you can go on with Resume game (対局再開).
• Against the CPU you can choose the board size, the strength and your color (Black, White or let the game choose). You can use Hint (ヒント) up to five times per game.

How the CPU works and its levels

The CPU on this site plays many trial games to the end for each candidate move and picks the move that wins most often (Monte Carlo tree search). In these trial games, it favors moves that capture stones, moves that escape from atari, and common stone shapes.

• Lv.1 Novice: reads only a little and sometimes plays other moves. For players who have just learned the rules.
• Lv.2 Beginner: plays with the basics of capturing and escaping in mind.
• Lv.3 Intermediate: spends 1–2 seconds per move and reads ahead.
• Lv.4 Advanced: spends about 3 seconds per move and reads the deepest. Hints use this level.

Example: counting at the end of a game

Here is how Japanese counting works, using made-up numbers. If Black has 30 points of territory and has captured 3 stones (prisoners), Black has 33 points. If White has 25 points of territory and 2 prisoners, that makes 27; add 6.5 points of komi and White has 33.5. In this case, White wins by half a point. Because komi includes a half point, there are no draws.

Tips

• In the opening, start from the four corners to secure territory efficiently. The basic order is "corners, sides, center".
• Rather than capturing stones, focus first on keeping your own stones connected so they cannot be cut.
• Start on the 9×9 board to get used to capturing stones and surrounding territory, then move on to 13×13 and 19×19.
• When you put your opponent's stones in atari (one liberty left), check before chasing them that their escape will not leave your own stones weak.
• In the endgame, whoever first plays the moves that settle the borders of territory (yose) gains. Play the biggest ones first.

Frequently asked questions

Can I play if I am new to Go?

The rules come down to two things: capturing stones and surrounding territory. Start with the CPU (Novice) on the 9×9 board to get used to capturing stones.

How is it different from shogi?

In shogi you move pieces to checkmate the king. In Go you place stones and compete for territory.

What if the dead stones are judged wrong?

On the screen after the game ends, tap a stone to switch it between dead and alive. In online games, the game ends when both players agree on the count.

Is Go free to play?

Yes, it costs nothing. Games against the CPU and solo modes work right away without signing in. Online play (random matches and private rooms) and saving stats or leaderboard scores require signing in with a Google account. To play with a friend, your friend also needs to create an account and register as your friend.

More board games

• Connect 4
• Minishogi
• Four-Player Shogi
• Gunjin Shogi
• Honeycomb
• Checkers