Title: Rules FAQ

Author: Robert Jasiek <jasiek_at_snafu.de>

Frequency: monthly

Last Update: 2009-02-12; First Day: 1999-04-12

Distribution: rec.games.go

Copyright: free non-commercial usage for promotion

0 CONTENTS

1 Purpose of this Paper

2 Information for Beginners

3 Important Concepts

4 Particular Rules

5 Troublesome Details

6 Tournament Rules

7 Links

1 PURPOSE OF THIS PAPER

This paper is a basic reference for important rules terms,

rules, and tournament rules. Beginners should read

especially chapters 2 and 3, players chapters 3 to 5,

tournament players and organizers chapter 6.

2 INFORMATION FOR BEGINNERS

2.1 What Must I Know as a Beginner?

The game is played on a grid board. Typically it has 19x19 

intersections, but 9x9 are also fine. Two players compete. 

The first player uses black stones, the other white.

The players alternate. A player may play or pass. Playing

is putting one's own stone on an empty intersection and

removing any surrounded opposing stones. To avoid 

cycles, a play may not recreate any prior configuration of 

all stones on the board.

Two successive passes end the game. Then the player with 

more intersections wins. Intersections are his if only his 

stones occupy or surround them.

2.2 Which Rules do I Need as a Beginner?

You can play with short rules as in 2.1. Other rules may

be different, but the game is the same, i. e. strategy,

tactics, and the score do not change. Extremely rare

exceptions confirm this rule.

The winner can be determined by area or by territory. 

Either includes empty intersections surrounded only by own

stones. While area adds intersections occupied by own 

stones, territory adds opposing prisoners instead.

All rules, except short rules, have further phases after

alternation and before scoring. Towards a game end it is

often clear which stones will be removed. The additional

phases allow the players to agree on which stones shall be

removed. Thereby final removals do not require alternation.

Whether you score by area or by territory or whether you

remove by alternation or by agreement should mainly depend

on which rules are used by people you play with.

2.3 Which Rules Should I Teach?

One possibility is to use a board with 9x9 intersections,

short rules as in 2.1, and count each player's score by

using a finger to scan the board for his intersections.

3 IMPORTANT CONCEPTS

While strategy and tactics virtually remain the same,

concepts vary in different rules. However, the following

gives a comprehensive overview on standard terms.

3.1 Stone, String

The physical device that colours one intersection in a

play is a STONE. Two intersections of the board are 

ADJACENT if they have a line but no intersection between 

them. Two intersections with either black, white, or no 

stones on them are CONNECTED if they are adjacent or if 

there is a chain of adjacent intersections of their type 

between them. A REGION consists of an intersection and 

any intersections connected to it. A black or white

region is called a STRING.

3.2 Surrounded

An intersection of one colour is SURROUNDED by another

colour if each leaving path reaches the other colour first

after the one colour. Hereby it can only be surrounded 

black by white, white by black, empty by black, or empty 

by white. A region can be surrounded. For strings there is 

an alternative notion of no liberty (or breath). A LIBERTY 

of a string is an empty intersection adjacent to it. Thus 

a string is surrounded if and only if it has no liberty.

3.3 Removal, Suicide

A removal empties the intersections of surrounded stones

if there are any. Hereby removal of opposing stones is

executed first, if necessary. Rules may either require or

forbid removal of own stones. This is called suicide or no

suicide. In practice, suicide might be used for so called ko

fights or in capturing races.

3.4 Capture, Prisoner

Rules that score territory call a removal a capture 

because all removed stones are seriously kept as prisoners.

3.5 Move, Play, Pass

The players have alternate turns. On each turn a player makes

a move that is either a play or a pass. A play places one's 

own stone on an empty intersection. It can then include 

removal of surrounded stones, if any. A pass merely continues

alternation by giving the opponent the next turn.

3.6 Compensation

The first move advantage by black can be compensated by

compensation points (komi) that are added to the white score 

after the game end. Komi can be adjusted by 0.5 to avoid 

ties. Today integer values for komi for 19x19 boards 

typically range between 5 and 7. For 13x13 boards one should

use 8, for 9x9 boards 6; however, there is no real consensus

for small board komi values yet. -

A weaker player (black) can get the right to place an agreed

number of compensation stones (handicap) before white's first 

play. Rules may allow free or fixed handicap. Free handicap 

does not apply any restriction. Fixed handicap requires 

traditional placement on set intersections.

3.7 Phases

Normally, a game consists of the phases alternation, 

agreement, scoring. A game stop is between alternation and 

agreement, the game end is between agreement and scoring, 

and after scoring both players accept the counted score as 

the result. The main part of the game is the alternation 

phase. Special rules are invoked after it. Typically, two 

successive passes in alternation are the game stop and start 

the agreement phase. In it the players may agree on strings 

to be removed. If they agree, then they remove those strings

from the board; this ends the game. Sometimes they might 

disagree, then no strings are removed but alternation is 

resumed as if the last game stop did not occur.

3.8 Recreation

The position is the pattern of black and white stones on the

board. Without extra rule a position might be repeated 

infinitely. The easiest rule to prohibit this says: A play 

may not recreate a position. This refers to positions after 

completion of plays, i.e. after possible removals. The rule 

is called "superko". -

Some rules use concepts different from superko. They combine

a "2-play rule" with a "long cycle rule". The first says: 

Two successive plays may not recreate a position. The second 

says: If a position is recreated after more than two moves, 

then the game ends either immediately or, as a variant, as

soon as the players agree, with the result "without result".

In practice the 2-play rule is sufficient for almost all

cases. It handles the relevant standard pattern of two

adjacent intersections. For superko this is just a special

application.

3.9 Scoring

The score is the result after the game end as defined by 

the rules. There are two different scoring methods: area 

scoring and territory scoring. Rules use one of them. Both 

give the same result in almost all cases and both evaluate 

the difference of the black and the white scores. A player's 

AREA score is the sum of intersections with own stones and 

of empty intersections surrounded only by own stones. Simply

speaking, a player's TERRITORY score is the sum of empty 

intersections surrounded only by own stones and of prisoners

of opposing colour. With both scoring methods empty 

intersections that are not surrounded by either black or 

white are neutral.

3.10 Counting

A score must be determined by some mechanical procedure in 

practice; this is called counting