Go (Weiqi)

How to play Go (Weiqi)

Go — known as Weiqi in China, Baduk in Korea and Igo in Japan — is the oldest board game still played in its original form, with a history stretching back more than 2,500 years. Two players, Black and White, take turns placing stones on the intersections of a grid, competing to surround more of the board than the opponent. The rules are astonishingly simple, yet the game is so deep that it remained the last classic board game where top humans held out against computers for decades. This version uses a friendly 9×9 board — quick to finish and perfect for learning — with the option to step up to 13×13. Play a friend on the same screen, or challenge the computer at three difficulty levels and earn ranking points for every win.

The goal

The goal is to control more of the board than your opponent by the time both players stop playing. Your score is the number of points you occupy with stones plus the empty points your stones surround — your territory. White is given a fixed bonus called komi (6.5 points on this board) to make up for moving second. When both players pass one after the other, the board is counted and the higher score wins. You do not have to capture anything to win; capturing is simply one tool for taking territory.

The board and the stones

Go is played on the crossing points (intersections) of a grid, not inside the squares. The full professional board is 19×19, but smaller boards play exactly the same way and finish far faster, so this app starts you on 9×9 with 81 points; you can switch to 13×13 (169 points) for a longer game. Black always plays first. A stone never moves once placed — it stays where it is until it is captured and lifted off the board. Star points (the small marked dots) help you judge distance, the last move is marked, and the number of stones each side has captured is shown above the board.

Rules of play

• Black plays first. Players then alternate, each placing one stone of their own colour on any empty intersection. Instead of playing a stone you may also choose to pass.
• Stones of the same colour that touch along the grid lines — up, down, left or right, never diagonally — form a single connected group and live or die together.
• The empty points directly next to a stone or group are its liberties. A group is captured and removed from the board the instant it has no liberties left.
• When you place a stone, first remove any enemy group it leaves with zero liberties, then check your own stone. You may not make a move that leaves your own group with no liberties (this is “suicide”) — unless that same move captures enemy stones, which frees liberties and makes it legal.
• The ko rule forbids an immediate recapture that would repeat the previous board position; you must play elsewhere for one move first (see below).
• The game ends when both players pass one after the other. The board is then scored by area, and the player with the higher total — after adding White’s komi — wins.

Liberties, groups and capture

Liberties are the heart of Go. Picture a single stone in the middle of the board: it has four liberties, the four empty points beside it. Fill all four with enemy stones and it is captured. Stones connect into groups by touching along the lines, and a group shares all of its liberties, so a large group with many empty neighbours is hard to kill, while a group squeezed down to a single liberty is “in atari” — one move away from capture. Strong play is largely about keeping your own groups breathing while taking away the opponent’s liberties. An “eye” is an empty point completely surrounded by one colour; a group with two separate eyes can never be filled in and is permanently alive, which is the key to keeping groups safe.

The ko rule

Ko (from a word meaning “eternity”) is the rule that stops the game looping forever. In certain shapes you can capture a single enemy stone, and your opponent could immediately recapture your stone, returning the board to exactly the position before — which could repeat endlessly. The ko rule forbids that instant recapture: after such a single-stone capture, the point that was just taken is marked forbidden for the opponent’s very next move (shown here as a small red square). They must play somewhere else first — often a “ko threat” you have to answer — and only then may the ko point be retaken. This app uses the classic simple-ko rule; passing or playing any other move clears the ban.

Passing and ending the game

You are never forced to play a stone. If you have no useful move — or you believe the borders are settled — you may pass and hand the turn to your opponent. Passing early throws away a move, so it usually only makes sense at the very end. When both players pass one after the other, the game is over and the board is counted. Finishing a game is therefore a two-step handshake: play out the boundaries, then both pass to agree that the game is done.

Scoring: area and komi

This app uses area scoring (also called Chinese scoring). At the end, every empty region is examined: if it borders stones of only one colour, all of its points become that colour’s territory; if it borders both colours it is neutral (called dame) and counts for nobody. The same holds for a seki — a mutual-life standoff — which is simply left as no-one’s territory. Your final score is your stones on the board plus your territory, and White adds the 6.5-point komi. The higher total wins. For an accurate count, play until only the boundaries remain and any clearly dead stones have been captured, because the counter scores the position exactly as it stands.

Playing the computer (ranked)

In “Go vs Computer” you choose your colour, a board size and one of three difficulty levels. Because Go is far too complex for the brute-force search used by chess engines, the computer here plays with a custom Go heuristic: it reads captures and ataris, defends its own stones when they are threatened, avoids putting itself into self-atari, keeps away from filling its own eyes, and fights over contested groups. Easy plays loosely and makes plenty of mistakes so beginners can win; Normal plays the solid heuristic move; Expert also looks one move ahead over its best candidates. It runs entirely on your device, so it works offline. Beat it to earn ranking points — Easy +10, Normal +30, Expert +100 — and sign in to record your best result on the leaderboard. Remember to pass once the borders are settled: two passes end the game and trigger the count.

Strategy tips

• On a small board, play your first stones a little away from the very edge — around the third line and the star points. Stones on the first or second line make territory too slowly, while stones too high in the centre are hard to turn into secure points.
• Make your groups strong before you attack. A group with plenty of liberties and access to the centre can fight; a weak group with few liberties becomes a target that hands your opponent free profit.
• Learn to see liberties and atari. Before a contact fight, count how many liberties each group has — whoever runs out first is captured. Putting an enemy group in atari is powerful, but only if you can actually follow through and take it.
• Aim for two eyes. A group with two genuine, separate eyes is unconditionally alive and can never be captured, so securing eye space for a group under attack is often worth more than grabbing a few extra points elsewhere.
• Balance territory and influence. Sometimes a solid corner or side is best; other times a wall facing the open board is worth more. Don’t answer every move locally — look for the biggest area still open and play there first.

Frequently asked questions