Games - Rules of Go

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	Games - Rules of Go

This is an in-depth discussion of the rules of Go.

Note: While the basic idea of go, conveyed by the outline rules given first, is not particularly complex, there are numerous subtle points which are not required study when first starting to play.

Basic Rules

Players

Rule: There are the two players, called Black and White.

Go is a game between two players.

The equipment

The board

Rule: Go is played on a board. The board is a grid of 19 horizontal and 19 vertical lines.

Beginners might prefer to play on a small board with 9 horizontal and 9 vertical lines (9 × 9 board). On this board learning tactics is easier and one is not confused by the complex strategies seen on big boards.

After having gained some experience (having played, say, 100 games), one can switch to the regular 19x19 board. Some teachers recommend moving up to a 13 × 13 board as an intermediate step, and this board is adequate for social players.

A point on the grid where a horizontal line meets a vertical line is called an intersection.

There are 361 intersections on the regular 19 × 19 board. In the following diagram, the mark (red circle) indicates one of the 25 intersections of the small 5 × 5 board:

(To save space, most diagrams show small boards. Here we have a 5 × 5 board.)

Stones

Rule: There are black and white stones.

The player Black uses black stones, the player White uses white stones. There is an unlimited supply of stones. The diagram shows some stones on some intersections of the board:

The state of stones on the board

Chain of connected stones

Definition: A chain consists of one stone or of several stones that are of the same colour and mutually connected via lines of the grid.

This is a chain of 6 black stones:

Liberty

Definition: A liberty of a chain is an empty intersection adjacent to it.

The marked intersections (red circles) are the liberties of the black chain:

Removal

Rule: A play removes any opposing chains without liberty.

Before the play:

The play:

After the play:

In most cases, a play does not remove any chain. In other cases, a play might also remove a bigger chain, which consists of several stones. In yet other cases, a play might also remove two, three, or four opposing chains, if it takes away the last liberty of each of them.

Existence

Rule: A played stone is existent on the board until the game's end, provided it is not taken in a removing play (at which point it becomes nonexistent).

Play

Alternate play

Rule: The players alternate. Black starts.

Before Black plays first, the board is empty:

Black makes a first play on one of the intersections:

Then White makes a second play somewhere:

The game will continue with Black and White alternating.

Play or pass

Rule: On his turn, a player makes either a play or a pass.

Normally, the player having the turn makes a play.

Empty intersection

Rule: When a player makes a play, he or she puts one stone of his or her colour on an empty intersection.

The following diagram shows how Black could make a play:

No suicide

Rule: It is prohibited to place a stone where it would have no liberties (or be a part of a larger chain with no liberties). The exception is when the stone completes a capture of an opponent's chain.

Note: Some Go rulesets allow suicide. The chain with no liberties is removed from the board.

Ko (no repetition of the same shape)

Rule: If recapturing that stone would recreate the same board position from the previous move, the position is called ko, and the recapturing move is illegal.

This "basic ko rule" is adequate for the simplest kind of ko, which occurs when two single stones could otherwise recapture each other indefinitely. This situation occurs in most games and often has a major or even decisive effect on the result. To prevent endless repetition, the rule of ko forbids plays that would repeat the previous board position. A player may not recapture on their next move and must play elsewhere (or pass). After a new move, the board position will be different, and the stone may then be recaptured.

Other positions which could lead to an endlessly repeating position are rare enough that many frequent players never encounter them; their treatment depends on what ruleset is being used. Under some rulesets, such games may be considered drawn if neither player opts to escape the loop by playing elsewhere (as a player with an overwhelming lead might be inclined to do). The AGA and New Zealand rule sets have a "superko" rule forbidding any move that repeats any previous board position. The Ing rules feature a complicated distinction between "fighting" and "disturbing" ko.

[ Visit the complete Wikipedia entry for Rules of Go ]

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