How do you win at Go?
The player who controls more of the board at the end wins. Black moves first, and players take turns placing one stone on an empty intersection.
Go is called Baduk in Korea, Weiqi in China and Igo in Japan, and it is one of the oldest board games still played. Stones never move once placed, but a group that gets completely surrounded is captured and removed. When both players pass in a row, the game ends and the board is counted. Resigning ends the game at once.
How do you capture stones in Go?
A group is captured when every liberty (adjacent empty point) is filled by the opponent. Stones of one color that touch horizontally or vertically form a single group that lives or dies together.
A lone stone in the middle has four liberties, on the edge three, in the corner two. A group with only one liberty left is in atari and must escape or capture something. You may not play a move that leaves your own group with no liberties (suicide), unless that move captures enemy stones first and so gains liberties.
| Term | Meaning |
|---|---|
| Liberty | An empty point next to a group, horizontally or vertically |
| Atari | A group with one liberty left, about to be captured |
| Suicide | A move that removes your own last liberty without capturing. Not allowed |
| Ko | A shape where one stone could be recaptured back and forth. Immediate recapture is banned |
| Eye | An empty point surrounded by your stones. Two separate eyes make a group safe forever |
| Komi | Points added to White to make up for Black moving first. 6.5 here |
What is the ko rule in Go?
Ko stops an endless loop of capturing one stone back and forth. After a single stone is captured in a ko, the opponent cannot recapture right away and must play somewhere else first.
This site remembers the whole board and blocks any move that would bring back the exact position from before your opponent's last move (the simple ko rule). Banned points show a red cross when you hover. The usual trick is to play a threat elsewhere that your opponent has to answer, a ko threat, and then retake.
Why do beginners start on a 9x9 board?
A 9x9 game is short, usually about ten minutes, and fights begin on the first few moves, so you learn the rules by playing them.
The full 19x19 board has 361 points and games often run past 200 moves. A common path is 9x9 (81 points) for capturing, ko and life and death, then 13x13 (169 points) to learn how corners and sides divide up, then 19x19. Both vs Computer and 2 Players work on every board size.
How do I pick the computer's rank and handicap?
If you are new, start at 30 kyu or 25 kyu and move up a step after two wins in a row. If it is still too hard, take a handicap and start with extra black stones on the board.
The computer has seven ranks: 30, 25, 20, 18, 15, 12 and 10 kyu. Higher ranks read more playouts per move, and the lowest ranks sometimes play a random move. In computer vs computer tests each rank beats the ones below it, but the labels are rough strength guides, not official ratings from a Go club or server. On bigger boards the computer is relatively weaker at the same rank.
In a handicap game the weaker player takes Black and places 2 to 9 stones on the star points before the game, then White moves first. A common rule of thumb is one stone per rank of difference. The 9x9 board allows up to 5 stones. Because this site uses area scoring, White gets komi equal to the handicap minus 0.5 (for example 3.5 points in a 4 stone game).
| Stones | Where they go |
|---|---|
| 2 to 4 | Corner star points, one by one |
| 5 | Four corners plus the center (tengen) |
| 6 to 9 | Four corners plus side star points, and the center for 7 and 9 |
How is Go scored, and what is komi?
This site uses area scoring (Chinese rules). Your score is your living stones on the board plus the empty points surrounded only by your stones, and White adds 6.5 points of komi.
Two passes in a row start the counting step. The computer guesses which stones are dead and shows them faded; tap any group to mark it dead or alive. Dead stones count as captured, so their points go to the other side. Press Count and you get a result such as "Black 41 vs White 46.5 (incl. 6.5 komi). White wins by 5.5." The half point means there are no ties.
Korean and Japanese rules use territory scoring, which counts surrounded empty points plus captured stones, and Korean events also give 6.5 komi. The numbers come out differently, but the winner is almost always the same and the margin rarely differs by more than one point. Area scoring is friendlier for beginners because playing inside your own area never costs you anything.
Go tips for beginners
- Corners first, then sides, then the center. In a corner two board edges act as walls, so you need the fewest stones to make points.
- Check for atari before every move. Save your own group with one liberty, and look for enemy stones you can capture.
- Stay connected. Many separate weak groups are hard to keep alive. A one point jump keeps stones linked.
- Make two eyes. A group with two separate eyes can never be captured. Give a chased group room to build them.
- Do not invade too deep. Stones far inside your opponent's area rarely live. Growing your own area is often worth more.
The computer uses Monte Carlo tree search: it plays out thousands to tens of thousands of quick games to the end and picks the move that wins most often. It resigns when its chances are very low, and if you pass while it is already ahead, it passes too. Lower ranks look at far fewer games and sometimes play at random, so they make plenty of mistakes.
Controls
- Mouse: click an empty point to play. Hovering shows a faded stone, and a red cross marks illegal points.
- Touch: tap once to mark the point, then tap the same point again to play.
- Pass and Resign: Pass skips your turn. Resign needs two presses so you do not hit it by accident.
- Undo: against the computer it takes back the computer's move and yours together. During counting it returns to before the passes.
- Counting: tap a group to mark it dead, tap again to bring it back. Small squares show who owns each point.