The Complete Rules of Go

  1. Go is played by two players. Each has a supply of stones of one color. A stone is a small, round, hard playing piece of a single color, either black or white. Stones are made of glass, seashell, slate, or plastic. Play proceeds on a board containing a square grid of black lines. Common grid sizes are 6x6 (or 7x7) (for learning the rules), 9x9 and 13x13 (for quick games), and the standard pattern of 19x19 lines.

  2. Players alternate making moves. A move consists of placing a stone of the player's color on the board, possibly capturing opponent's stones. Either player may pass at their turn instead of placing a stone. When players believe that the game is over, they pass. Players should not pass if they believe that the score can be changed by further play.

  3. The player with black stones plays first. Usually the stronger player takes white.

  4. Stones are played on intersections, including the intersections at the edge and corners of the board's grid.

  5. Stones do not move after being played.

  6. Handicap is an initial pattern of black stones granted to a player of lesser rank. Handicaps permit players of unequal rank to play each other. Handicaps are placed in specific patterns, starting with the intersections that are marked with small black dots. After the handicap stones are placed on the board, white moves first.

  7. Komi is an optional number of points added to white's score to compensate for the fact that black moved first. On a 9x9 board, komi is usually 6.5 points; on 19x19 it is usually 5.5 points. The half point guarantees that games will not end in a draw (tie). The value of komi results from the fact that one stone played at the start of a game on a 19x19 board is worth approximately 10 points by the end of the game, assuming that the players play well and have a small difference in rank.

  8. A game ends when both players agree that they can make no move that increases their score. This agreement is indicated by two successive passes.

  9. A string of stones are one or more stones of one color that are all touching (adjacent) and 'joined' to each other by horizontal or vertical lines on the board (diagonals do not join stones to form strings).

  10. The empty adjacent intersections of a string are called the string's liberties .

  11. If the number of liberties of a string is one, the stones are said to be in atari and will be captured whenever the opponent places a stone so as to change the number of liberties to zero.

  12. A stone may not be placed on the board if it would then have zero liberties, except when it captures opponent strings. This is known as the no self-capture or no suicide rule.

  13. Groups of stones are strings of the same color that are 'connected' to each other by short, non-adjacent gaps. Usually, but not always, only the following kinds of connection are allowed when defining a group: diagonal, single-point skip, double-point skip, small knight's move, and large knight's move (the latter two terms derive from chess).

  14. Strings of stones are captured by either player whose move causes one or more opponent strings to have zero liberties. The opponent strings must be removed from the board immediately and their stones are counted as prisoners of the player making the move that captured the strings. The capturing stone remains on the board.

    Note that a group that surrounds two or more nonadjacent empty points (such points are called eyes ) cannot be captured, because a player cannot play in both points in one move (the player cannot play in either empty point in one move because of the rule of no self-capture). A group that cannot be captured is called a living group . A group that can be captured (that is, does not have the possibility to form two eyes) is called a dead group . A dead group cannot gain life unless surrounding opponent stones are captured.

  15. The rule of ko prohibits any move that would cause any previous board position (pattern of stones) to be repeated. This rule applies to a situation where capturing the same strings could otherwise continue forever.

  16. Seki (dual life) is the situation in adjacent groups of stones where both players do not want to move because any move would place their own strings in atari. Such stones are left on the board and are ignored during scoring.

  17. A game is scored at the end of the game and the player with the higher score wins. There are a number of different sets of rules for scoring, including American, Japanese, Korean, and Chinese. The scoring rules described here are the most common rules for informal play, a simplification of the Japanese rules.

  18. Territory consists of all empty points that are completely surrounded by stones of the player's color. The surrounding stones need not belong to the same string. For the purpose of counting territory, edge lines act like stones. Empty points that are surrounded by stones of both colors are called dame (neutral points); they do not define territory and are ignored during scoring. Empty points inside groups in seki are not counted, even though they may be surrounded by stones of the same color.

  19. Before scoring, dead stones are usually removed from the board, to become prisoners as though they had been captured in the usual way. This simplifies scoring. Some players like to rearrange the remaining stones so as to make all territory form rectangular areas, for ease of counting the points of territory.

  20. The score for a player is the total of the player's points of territory and prisoners.

  21. Players have levels of play called rank (ranking, rating). Two players whose rank differs by two points, for example, tend to win the same number of 19x19 games with each other when the weaker player starts with a handicap of two points, and so on for larger differences in rank. Ranks are a scale that starts at about 35 kyu for newcomers to the game and decreases with improvement in play until it reaches one kyu. After that it continues at one dan and increases up to a current maximum of about 9 dan. These are sometimes called the Amateur ranks. Professional players usually have a strength level greater than this; their rank is on another 'dan' scale that starts at one dan/professional (1p) and increases to about 9 dan/professional.

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