Rules of The Game
"The rules of go are so elegant, organic, and rigorously logical that if intelligent life forms exist elsewhere in the universe, they almost certainly play go."
-Edward Lasker, International Chess Master There are two players in go, Black and White, each represented by black and white pieces which are called stones. The standard board is a 19x19 grid with a total of 361 points on the board, but there are also smaller boards used for teaching the game.
Black always goes first, which is a little different for people who play chess. Another thing which is different is that in go, stones are placed on the intersections of the lines rather than within the squares made by the lines. This does not change the relationship of one point to another, though. Throughout this article, I will follow the traditional nomenclature of referring to the player playing Black as "he" and the one playing White as "she." |
Capture
A single stone is added each turn, and none may be moved on the board, though they may be removed from the board. Removal, or capture, is done by surrounding a stone on all of its sides. In diagram 1, the single black stone will be captured if the marked point is played by White. This situation is called “atari” in Japanese. Diagram 2 shows the resulting position of White’s play. The black stone has been placed in the lid of White’s bowl of stones to be accounted for in the scoring at the end of the game. After the capture in diagram 2, black may not play at A because that point is completely surrounded by White’s stones, and so, it would be automatically captured. If Black were to save his stone from potential capture by extending from the atari as in diagram 3, the two black stones would form a single unit, called a group, because they share a common edge (in the strictest sense of the word, which I am adopting here, a diagonal play would not be considered a single group because an edge would not be shared by the two stones). To capture these two stones, White must surround Black’s every free intersection, that is, every "liberty," for these two stones, which are marked in diagram 3. White’s capture of the black stones would result in the position of diagram 4. Unlike in diagram 2, Black is now free to play at either A or B because each point would have a free liberty at the other. |
A Living Shape
Although this is not a rule, it is a good principle to know and follows the logic of the rules of capture given above: A group which has two separate points which it surrounds, called “eyes” or “houses,” can never be captured. In diagram 5, Black has two separate eyes at A and B. The edge of the board is a sort of border for both players, so these two eyes are completely enclosed by Black. On account of that, this group is deemed to have "life" and cannot be captured. This is because White could not play at either point because each one would be “suicide” for a White stone, that is, it would be captured itself because of its lack of liberties. Because of this, Black’s group as it is can never be captured by White. The situation is different in diagram 6 because here, although Black has two "eyes," they are not separated by a stone and are as good as a single eye. White can play at A or B, and Black may capture at the other point resulting in a position similar to the one in diagram 7. After diagram 7, White may play at A and kill Black in a single move. This move may look like suicide for White, but it is not the case because the turn is not yet over. The black stones, being completely surrounded, must first be removed, and then the liberties of White’s played stone are counted, and only then is the turn ended. In diagram 8, White’s stone would have two revealed liberties at A and B after the captured black stones are removed. The reason why diagram 5 is different from diagram 6 is that if White were to play at either A or B in the former diagram, Black would always have another liberty at the other point and thus perpetually avoid capture. The situation in diagram 6 will lead to diagram 7, and Black will be left with only one eye, and his group may be captured as in diagram 8. |
The Ko
In diagram 9, the white stone which is marked may be captured by Black with a move at A. This move might look like suicide, but the marked white stone will first be removed because of its complete enclosure by Black, and Black will have one revealed liberty at that spot as seen in diagram 10, after the turn is completed. The rule of the ko states that White now cannot immediately capture Black’s marked stone at B. This is because the position would revert to the same one as in diagram 9, which was one move ago. White must first change the the configuration of the stones on the board before she is allowed to play at B by playing somewhere else, thus changing the board. This situation is called a “ko” or “ko fight.” In diagram 11, after the exchange of White 1 and Black 2, White is now free to play at B and capture Black's stone. This is because the configuration of the stones on the board has changed. The exchange of those two moves could have been made anywhere on the board and still allowed White to capture at B after it was is done. In a case like that, the local shape of the stones would not have changed, but the board would have done so, so, accordingly, White would be free to play at B. Of course, here, Black may decline to answer White 1 at Black 2 or some other point and instead save his marked stone by playing at B himself, thus ending the ko in his favor. |
![Picture](/uploads/3/1/3/6/31363285/go-score-white-o-black-x_orig.png)
Territory and Scoring
As fun as capturing your opponent’s stones may be, the goal of the game is to claim most of the board as your own. Claiming most of the board is done by surrounding more of its vacant points for yourself than your opponent can do for himself.
Every vacant intersection which your stones surround is counted as one point for your score. Thus, it may be said, "a point on the board is a point for the score." In diagram 12, Black would surround 6 points (marked by x's) and White would have 8 (marked by o's). Thus, White would win by 2 points if the game were to end at this moment. However, in this example, there is much more of the board left for grabs, so the two players (particularly Black) would not want to end here.
Every game of go will eventually come to a conclusion when both players sequentially pass their turns in order to avoid losses to their territories. This is because the game will come to a point in time when all of the territory of the board will be occupied by either player and the borders will be defined, and by placing a stone on any point of one's own territory, it would be reduced (only vacant points are counted for the score), and by placing a stone in the opponent's territory without hope for its potential life, it would most likely be captured or ignored by the opponent and counted as "dead," which is as good as giving him a prisoner for his lid. For the first few times of playing go, judging when this point will arrive may be difficult, but with practice, it will take only a brief sweep of the board to see.
Before the two players' territories are counted, the stones which both players agree could not live are removed from the board and placed in the lids of the bowls with any stones that may have been captured throughout the course of the game. These “prisoners” are then used to fill in, thus remove, points of the opponent’s territory.
Customarily, the player holding White is given an extra 6.5 points of 'komi,' to compensate for Black's first move advantage. This would mean that if both players secured fifty points of territory each, White would win by 6.5 points. The half-point is used to break ties in White’s favor (it is not always used, though). It is not uncommon for a stronger player to play as White without komi against a weaker player. This is sometimes called a "one stone handicap" (see "handicaps" below).
After all of this is taken into account, the final score can be tallied, and the difference between the two scores is the margin of victory, with the larger score winning over the smaller one.
As fun as capturing your opponent’s stones may be, the goal of the game is to claim most of the board as your own. Claiming most of the board is done by surrounding more of its vacant points for yourself than your opponent can do for himself.
Every vacant intersection which your stones surround is counted as one point for your score. Thus, it may be said, "a point on the board is a point for the score." In diagram 12, Black would surround 6 points (marked by x's) and White would have 8 (marked by o's). Thus, White would win by 2 points if the game were to end at this moment. However, in this example, there is much more of the board left for grabs, so the two players (particularly Black) would not want to end here.
Every game of go will eventually come to a conclusion when both players sequentially pass their turns in order to avoid losses to their territories. This is because the game will come to a point in time when all of the territory of the board will be occupied by either player and the borders will be defined, and by placing a stone on any point of one's own territory, it would be reduced (only vacant points are counted for the score), and by placing a stone in the opponent's territory without hope for its potential life, it would most likely be captured or ignored by the opponent and counted as "dead," which is as good as giving him a prisoner for his lid. For the first few times of playing go, judging when this point will arrive may be difficult, but with practice, it will take only a brief sweep of the board to see.
Before the two players' territories are counted, the stones which both players agree could not live are removed from the board and placed in the lids of the bowls with any stones that may have been captured throughout the course of the game. These “prisoners” are then used to fill in, thus remove, points of the opponent’s territory.
Customarily, the player holding White is given an extra 6.5 points of 'komi,' to compensate for Black's first move advantage. This would mean that if both players secured fifty points of territory each, White would win by 6.5 points. The half-point is used to break ties in White’s favor (it is not always used, though). It is not uncommon for a stronger player to play as White without komi against a weaker player. This is sometimes called a "one stone handicap" (see "handicaps" below).
After all of this is taken into account, the final score can be tallied, and the difference between the two scores is the margin of victory, with the larger score winning over the smaller one.
To put into practice of what was said above, let's look at an example on a 9x9 board. In diagram 13, the points marked with "x's" designate Black's territory and those marked with "o's" designate White's territory.
In the first step of calculating the score, all stones which have no hope of making "life" must be removed and placed into the lid of the opponent's bowl with any stones which were captured during the course of the game. For the sake of simplicity, let us say that no stones were captured during play. In diagram 13, the single white stone on the top of the board which is marked with an "x" is considered "dead," as well as all eight of the black stones which are marked with "o's," because they have no hope of making a living shape. White's large group of stones in the center does not technically have two separate eyes, but it would be impossible for Black to prevent two eyes from being formed without many free moves in a row, so the white group is deemed living. Sometimes, judging this can be difficult, but, like judging the point in time when the game has come to a close, as you play the game more, it will become almost second-nature. In the meantime, it would be good to have a more experienced player at hand whenever there are confusions on the status of a group's life. Returning to diagram 13, Black would have 14 points of territory (including the point under the captured stone from White) and the one captured stone from White. White would have 25 points of territory, 8 captured stones from Black, and 6.5 points of komi. The prisoners subtract from the opponent's score, so White would have 30.5 points and Black would have 6 points. The victory would go to White with a margin of 24.5 points. Instead of counting each point one by one, the stones may be moved to be arranged in boxes or other shapes for the ease of counting as in diagram 14. There is much freedom in how the players may go about this, but it must be kept in mind that the borders must not be shifted, lest the score be changed and the balances tipped. |
What you have read above describes the Japanese scoring system (also called "territory scoring"), which is what much of the world uses, but its main alternative, the Chinese scoring system (also called "area scoring"), may be seen below in the "Finer Points" section of this page. It is interesting to see the divergences in their approaches, but their tendency to nearly always render the same results.
Seki
A seki (also, "dual life or "mutual life," "bik" in Korean), is a special arrangement of stones in which two or more enemy groups which are touching each other do not each have two eyes, and thus neither one has a living shape. However, in a seki, neither group can attempt to capture the other without resulting in its own capture. Thus, each group is not living independently, yet neither is dead. Diagrams 15, 16, and 17 each show an instance of a seki. In diagram 15, neither White nor Black can play at A or B without expecting the other player to immediately capture his stones at the other point. This particular type of seki is called a "simple seki" in that no eyes are involved. In diagram 16, both groups in the seki have one eye each. Neither player can play at A without being captured by the other. Diagram 17 is quite odd in that it is a genuine instance of seki (neither A nor B may be played without one’s own capture), but it involves three groups, two white and one black. Each of the white groups has one eye, yet the black group has none. For the sake of illustration, it is assumed that the outer groups enclosing the seki's are themselves living. Otherwise, there would be no seki because one player may kill the stones on the outside to obtain more liberties and then proceed to kill the stones on the inside. This is called a "seki collapse". Under the Japanese scoring system, no enclosed points are counted for a player's score in seki and it is left unmodified. The area is simply ignored during the counting phase. Thus, in diagram 17, White would not get two points for his two eyes in seki. See the section on the Chinese scoring system to see how it handles counting points in seki. There are many other types of seki, with some being quite complicated, but as an introduction to the concept, I will not provide them here. Seki's are an interesting part of go. If one cannot find a way to kill a group outright, it may be profitable to consider forming either a ko or a seki. Winning a ko would reap more profit in that the opponent’s stones would be dead, but there is always a chance that the ko will be lost. A seki, once made, is a stable shape that eliminates any points for either player, so it may be profitable enough if the points eliminated were not yours to begin with, but rather, your opponent's. |
Conclusion
What you have read are the basic rules of go. This should be enough to resolve nearly every situation that may be faced on a go board. However, for the resolution of rare situations and other conventions, such as handicapping and alternate scoring methods, continue reading to the "finer points" section of this page.
What you have read are the basic rules of go. This should be enough to resolve nearly every situation that may be faced on a go board. However, for the resolution of rare situations and other conventions, such as handicapping and alternate scoring methods, continue reading to the "finer points" section of this page.
Finer Points And Other Interesting Things
You have just read the basic rules for go. But, there are some rare positions which may need additional commentary and sometimes a slight rewording of a rule to disambiguate. Alternate conventions of play are also listed such as giving handicap stones and using the Chinese scoring system to count points. And, to round it off, some musings on the 'perfect' amount of komi are offered.
You have just read the basic rules for go. But, there are some rare positions which may need additional commentary and sometimes a slight rewording of a rule to disambiguate. Alternate conventions of play are also listed such as giving handicap stones and using the Chinese scoring system to count points. And, to round it off, some musings on the 'perfect' amount of komi are offered.
Handicaps
While a normal game is begun on a blank board, a stronger player may give a weaker player a handicap of a given number of starting stones to offset the two's difference in ability. As a rule of thumb, each handicap stone is equivalent to one difference in 'kyu' ranking. There are eight standard placement patterns from a two-stone handicap to a nine-stone handicap. In these patterns, handicap stones are always placed on the "star points" of the board. A one-stone handicap may be considered as Black playing first without giving komi (first-move compensation points) to White.
A less common type of handicap is called "reverse komi" in which it is Black, not White, who receives the standard komi as well as the first move. This allows for a blank start, but also gives Black a large advantage. The eight standard handicap stone placements are shown below. Beyond nine stones, there is not a standard placement.
While a normal game is begun on a blank board, a stronger player may give a weaker player a handicap of a given number of starting stones to offset the two's difference in ability. As a rule of thumb, each handicap stone is equivalent to one difference in 'kyu' ranking. There are eight standard placement patterns from a two-stone handicap to a nine-stone handicap. In these patterns, handicap stones are always placed on the "star points" of the board. A one-stone handicap may be considered as Black playing first without giving komi (first-move compensation points) to White.
A less common type of handicap is called "reverse komi" in which it is Black, not White, who receives the standard komi as well as the first move. This allows for a blank start, but also gives Black a large advantage. The eight standard handicap stone placements are shown below. Beyond nine stones, there is not a standard placement.
Double Ko, Triple Ko, and Other Endless Cycles
Take a look at diagram 18. This presents a type of seki in that neither group on the inside of Black's outer wall of stones may capture the other (assuming that Black's outer wall remains alive). If Black were to play at 'A' to threaten the capture of White's group, White may respond by playing at 'B', reverting the situation to a position equivalent before Black's move, as in diagram 19. This can continue on and on without either group seizing the opportunity to capture the other. This is a 'double ko', and it can produce dual-life. Now, look at diagram 20. It is Black’s turn, and he must capture a stone at either ‘A’ or ‘C’ in order to avoid his own capture by White at ‘B’. So, Black takes the ko at ‘A’, resulting in diagram 21. Now, White is put in the same predicament which Black has just escaped. She has only one liberty, and must take Black’s stone at 'B' to gain a second liberty, resulting in diagram 22. By doing so, Black is again reduced to one liberty and must capture at 'C', resulting in diagram 23. This is an endless cycle which neither player may break without the capture of his group by his opponent because the position is always one where one of the groups will continuously be one move away from capture. It is called a "triple ko" because the cycle is caused by three simaeultaneaus ko's. There are two ways to handle the triple ko. One is to declare a draw, in which a result is not given for the game. The other is to implement a variation of the ko rule, called the superko rule. While the basic ko rule as I have explained it states that a whole board position may not be immediately reduplicated, the superko rule states that a whole board position may never be reduplicated. This would mean that in our triple ko example above, one player would eventually not be able to take another ko in this sequence in order to give himself more liberties because the exact board position would have eventually already occurred in a previous instance of the ko cycle. He must then play elsewhere, perhaps threatening something as he would in a normal ko, and his opponent then may choose either to answer his move (and thus allow him to continue the triple-ko and potentially win it) or ignore it and capture all of his stones in the triple ko. In this way, the triple ko is more or less like an extension of the regular ko. Thus, the rule of superko states that a whole board position may never be reduplicated apart from a passing move, which is really not a move at all. Another application of the super ko rule has to deal with the ‘suicide’ of stones, a self-capturing move. Now, look at diagram 24. White may not play at either ‘A’ nor ‘B’ because each point would result in the capture of his own stone which he would have just played. Thus, the board position would not have changed from the last move and the superko rule does not allow this to be. However, when concerned with the self capture of a group of stones as in diagram 25, the case is not so. If Black were to play at ‘A’, his two stones already present on the board and the one he would have just placed would be smothered of liberties and removed from the board in capture, resulting in diagram 26. Because the two stones that were already on the board would now not be, the board position has indeed changed. This is a viable threat to White as it threatens to reduce her "eyeshape" (potential to make two eyes for definite life) to a single eye if 'A' is not immediately played by her. However, both the Chinese and Japanese rulesets do not allow suicide of any kind, including group suicide as in diagram 25. It is probably not a point to push, but it is interesting to discuss group suicide in light of the superko rule. |
The Chinese Scoring System
The Chinese scoring system is the method of scoring traditionally used in China. It is older than the Japanese scoring system which Japan and Korea now use, and it is also nearly equivalent to it in the result which it gives. Sometimes, the Chinese scoring system is called "area scoring" to distinguish it from the Japanese system which is also called "territory scoring."
The main difference between the two scoring systems is that, while the Japanese count every vacant point which a player surrounds, the Chinese count those and also every stone which a player has on the board. Thus, every point on the board which a player occupies and controls, whether filled with a stone or empty, is counted toward his score. Furthermore, the Chinese scoring system does not account for prisoners in the way that the Japanese system does. Captured stones are simply returned to the bowls of their owners. An observant reader may notice that because each stone also counts as a point, removing a stone from the board removes a point from the opponent, and so this system is equivalent to the Japanese system, which counts captured stones as negative points to subtract from the opponent's score.
It is good to note that only one side need be counted in the Chinese scoring system. If that side sums up to half the board plus one and the designated komi, that player has won. Otherwise, he has lost. Empty intersections are typically counted first, and then the stones are arrayed in groups of ten and added to that score.
Due to the nature of the Chinese scoring system, the Chinese use 7.5 komi. This amount is actually equivalent to 6.5 komi under territory scoring. This is because a raise of the older 5.5 komi to the even-numbered 6.5 as the Japanese did would not change the outcome of a game under Chinese scoring due to the fact that a player’s score under Chinese scoring is nearly always odd-numbered.
Another thing which is peculiar to the Chinese scoring system is the counting of points in seki. For example, in diagram 17 above, White would gain two points from his two groups in seki because, although they are not independently living, they each surround one eye. The Japanese, however, do not count points in seki.
Finally, in the past, a 2 point tax was put on every separate group a player had on the board, giving incentive to link all of one's groups together. This is now no longer followed except under some theoretical rulesets such as the "mathematical rules of go".
Apart from the Japanese and Chinese scoring systems, there are a number of derivative scoring systems used in some parts of the world. Historically, Korea used its own counting system which treated prisoners as the Chinese scoring system does, returning them to the bowls of their owners, but it had all of the stones within one's territory removed apart from those bordering the opponent's stones. Leaving a stone in atari (one step away from capture) in this process was not allowed. After this, the player's vacant intersections were counted to determine the score.
The Chinese scoring system is the method of scoring traditionally used in China. It is older than the Japanese scoring system which Japan and Korea now use, and it is also nearly equivalent to it in the result which it gives. Sometimes, the Chinese scoring system is called "area scoring" to distinguish it from the Japanese system which is also called "territory scoring."
The main difference between the two scoring systems is that, while the Japanese count every vacant point which a player surrounds, the Chinese count those and also every stone which a player has on the board. Thus, every point on the board which a player occupies and controls, whether filled with a stone or empty, is counted toward his score. Furthermore, the Chinese scoring system does not account for prisoners in the way that the Japanese system does. Captured stones are simply returned to the bowls of their owners. An observant reader may notice that because each stone also counts as a point, removing a stone from the board removes a point from the opponent, and so this system is equivalent to the Japanese system, which counts captured stones as negative points to subtract from the opponent's score.
It is good to note that only one side need be counted in the Chinese scoring system. If that side sums up to half the board plus one and the designated komi, that player has won. Otherwise, he has lost. Empty intersections are typically counted first, and then the stones are arrayed in groups of ten and added to that score.
Due to the nature of the Chinese scoring system, the Chinese use 7.5 komi. This amount is actually equivalent to 6.5 komi under territory scoring. This is because a raise of the older 5.5 komi to the even-numbered 6.5 as the Japanese did would not change the outcome of a game under Chinese scoring due to the fact that a player’s score under Chinese scoring is nearly always odd-numbered.
Another thing which is peculiar to the Chinese scoring system is the counting of points in seki. For example, in diagram 17 above, White would gain two points from his two groups in seki because, although they are not independently living, they each surround one eye. The Japanese, however, do not count points in seki.
Finally, in the past, a 2 point tax was put on every separate group a player had on the board, giving incentive to link all of one's groups together. This is now no longer followed except under some theoretical rulesets such as the "mathematical rules of go".
Apart from the Japanese and Chinese scoring systems, there are a number of derivative scoring systems used in some parts of the world. Historically, Korea used its own counting system which treated prisoners as the Chinese scoring system does, returning them to the bowls of their owners, but it had all of the stones within one's territory removed apart from those bordering the opponent's stones. Leaving a stone in atari (one step away from capture) in this process was not allowed. After this, the player's vacant intersections were counted to determine the score.
Finding the Perfect Komi
Before the introduction of komi, Hon’inbo Shusaku, one of the greatest go players on record, when asked to comment on a game he had just won, simply said, “I had black.” Since the early 20th century, when komi was introduced, the value of komi has been raised from 4.5 upward and now sits at 6.5. Without komi, KataGo, a strong go-playing AI, puts White’s initial win percentage at 14% (give or take a hundreth). It should be noted, however, that this estimate is based on KataGo's superhuman play for both sides.
Before the introduction of komi, Hon’inbo Shusaku, one of the greatest go players on record, when asked to comment on a game he had just won, simply said, “I had black.” Since the early 20th century, when komi was introduced, the value of komi has been raised from 4.5 upward and now sits at 6.5. Without komi, KataGo, a strong go-playing AI, puts White’s initial win percentage at 14% (give or take a hundreth). It should be noted, however, that this estimate is based on KataGo's superhuman play for both sides.