What are the rules of Go

Introduction to the Go Rules

I basics

General

Go is a strategy and tactics game for two people. It is played on a grid board. One player uses black pieces, the other uses white pieces. They are placed on free intersections of the grid. The players take turns to place a stone.

To catch

A stone or several stones of one color connected by grid lines form a chain. Each chain must be adjacent to at least one free grid point via a grid line. Enemy chains without such a free grid point will be caught. The stones to be removed from the board, the prisoners, are kept until the end of the game.

Goal of the game

At the end of a game, the player with more points wins. Territory points and prisoners count. The area of ​​a player are the grid points, which are surrounded by stones of his color and thus dominated.

II special features

begin

Black begins the game.

compensation

Before the start of a game, both players can agree on compensation. For Black's first right to move, White usually receives 5.5 points, which are taken into account at the end of the game. Another possibility gives the weaker black player the balanced placement of handicap stones on the grid points marked for this instead of a first move.

No suicide

A move is prohibited if it does not allow the chain of the placed piece to have at least one free neighboring point.

To catch

A stone that has been set can also catch more than one enemy chain.

Ko

If a stone catches exactly one stone, the opponent may not catch it back immediately. This enables meaningful play.

Fit

Most of the time, a player will exercise his or her right to place a stone. Towards the end of the game, this doesn't always make sense. Then the player can say he is passing instead. This gives his opponent the right to move.

Playing

Alternating play fights for points. At some point, the scores can no longer be improved. Then the neutral points are filled and those points on which one has to re-examine within his area. Then both players pass. This ends the game and starts counting.

counting

There is a common way of counting. First, the prisoners are placed in areas of their color. Then the free areas are practically rearranged (e.g. blocks of ten). Finally, it is summed up and compared.

task

A player can end the game by giving up.

III life and death

After the end of the game and before counting, each chain is checked to see whether it is alive or dead. The stones of the dead chains become prisoners. All living stones remain on the board. They then enclose free board points in one color. This makes it clear who owns which area.

analysis

The analysis concerns the testing of life or death for chains. It is performed for each chain by means of an imaginary continuation of alternating play to see if a chain can be caught. The best possible moves of both players must be taken into account.

Theoretically, there can be very many imaginary continuations. In practice, in an analysis you make a selection that only includes variants that clearly distinguish life and death from one another. Such variants take into account the shapes occurring in the vicinity of a chain. And they all start with one move by the opponent.

Living chains that cannot be caught

The two white chains on the lower left are alive because they cannot be caught. Why? If Black wanted to catch one of them, he would have to start by taking one of the two free points between them. But that is suicide and therefore prohibited. So Black never has the opportunity to play a variant to catch.

The two individual free points are called eyes. As you can see, a chain lives with at least two eyes.

The same applies to the white chains in the middle: they too have two eyes; they cannot be caught and therefore live.

Now what about the black chain? She has no eyes in the strict sense. But as will be demonstrated below, it can always get two eyes, no matter which variant White should try to kill:

The two white chains on the top left are alive: both free points there are suicide for black.

The two white chains on the lower left are also alive:

In addition, the white chain at the top right is still alive. An exemplary variant is shown:

The life of the large black chain and the small black chain at the bottom right can be seen as follows:

Thus, in Example 2, seven chains have been shown to be alive because they cannot be caught - five white and two black chains.

coexistence

A peculiarity of life is the coexistence of black and white chains. You don't have two eyes, but you have shared free points.

There are two coexistence on the board. At the top right, the black and white chains have two free points in common (but no chain has even one eye). At the bottom right, the black and white chains have a common free point and each have an eye. The two coexistence are the possible basic forms for common life. In any case, no player is interested in killing an opposing chain first. He would have to occupy a common free point and the opponent could then immediately catch the attacker's chain. So no catching is possible and all the chains involved are alive.

There is an exception for coexistence in game evaluation: There is no area adjacent to coexistence.

In the example, in the upper coexistence, the common free points are not an area; in the lower coexistence, the two eyes are not in addition to the common free point.

Living chains that can be caught

The paradox of a living chain that can be caught is easy to explain: catching the chain enables a new stone of the same color to live. Here is a case in point:

The single black stone can be caught:

But this only leads to the new black stone 2, which cannot be caught. So the original black stone lives.

Dead chains

A chain is dead if it is not alive.

In Example 2 there are several chains that are dead: all those that are not alive. A large dead chain (the white one at the bottom right) shows how they are caught:

White can hardly defend himself and therefore fits. Black fills the free neighboring points. This shows the death of the white chain on the lower right (and the white chain above).

The four smallest black chains are also dead - white can catch any of them.

The white chain is dead; this should now be shown:

Black approaches from the outside. White makes a short attempt to defend himself with move 2 to threaten one eye, but Black 3 prevents that. The approach from outside continues to Black 15 (while White always passes). Now the position could be taken for a coexistence. But appearance is deceptive:

Black now takes the space for eyes from within. Whenever White only has one free neighbor point, he creates other space for himself by catching it. However, the space is getting smaller and smaller. And black always starts adding new space in such a way that white cannot then divide it into two parts for two eyes. After all, white is trapped. This shows that the original white chain is dead.

(The original black chain in the middle can be caught, but ultimately this only enables a new black stone that cannot be caught. That is, the chain is alive.)

Dead Ko

In the analysis the following applies to every knockout: If a player catches in the knockout, the opponent must first pass for this knockout before he can catch back. This means that the opponent passes and calls a Ko. Most of the time, the knockout is already resolved before the chance to catch it on the opponent's next move can be realized. The chain of such a Kos is dead.

In the top right corner is a knockout. Black 1 starts in the knockout. White wants to prevent losing all the stones and therefore passes with move 2 for the knockout in the top right. But Black 3 resolves the Ko by catching the last white chain. With this, White can no longer catch a Ko. It can also be seen that the original white chains are dead.

Removing dead chains

As soon as one has determined all dead chains in the analysis, they have to be removed. They become prisoners, and the area now clearly visible is to be counted.

Dead chains are given by the imaginary continuation of the alternating game. This means that there is no need to approach and even catch such chains by alternating play before the end of the game. In fact, it is unwise. With every approach move actually played you add a point. Such points do not count later in the evaluation because they are no longer free. You get lost.

This is what example 2 looks like after removing the dead stones. White took five more prisoners, Black eight. Now you can count.