An introduction to the game of Go

Go is a game originating from ancient China before 200 BC. It takes five minutes to learn the rules and an entire lifetime to master the game. In terms of strategic complexity Go is often compared to chess, but where as chess is best viewed as a single battle, go takes on the aspect of a global war with battles fought on many fronts.

Part of the fascination of Go is drawn from how a few simple rules can lead to such a complex game. Despite the sincere efforts of researchers it is still doubtful that a computer program will ever be able to match, let alone beat, professional players. To navigate a game of Go requires human intuition.

The rules of Go

Go is played on a board, by two players. The board is divided by vertical and horizontal lines. The game is played on the points where the lines intersect. A 19x19 board thus represents a playing field of 361 points, and a 9x9 board presents a more manageable 81 points.

The game starts with an empty board. Every point represents a valuable piece of territory. The object of the game is to surround more territory than your opponent. Territory is surrounded by the black and white player respectively by placing their stones on the board points. It is the privilege of the black player to make the first move.

The players now take turns placing one stone on the board. Once a stone has been placed it cannot be moved. The figure to the right shows a typical opening sequence. The numbers indicate the order in which the stones were placed on the board.

Note how each player tries to form a wall, by mapping out a section of the board which may later become solidly surrounded territory. The black player is attempting to surround territory in the upper right part of the board, while the white player is attempting to surround the lower left. It is however still too early to count potential territory as solid points, particularly since either player may try to invade the others sphere of influence.

Every point on the board is intersected by two lines, and these lines point to the four adjacent points. When two stones of the same color are placed on adjacent points we say that they are connected and form a group. In the image above there are two groups. The white stones 4 and 6 form a group, and the black stones 3 and 5 form a group.

Once a stone is placed on the board it is intersected by two lines. Each of the lines points to two adjacent point. If an adjacent point is empty we call it a liberty. A solitary stone, like black 1 above, has four liberties. Stones in a group share liberties, the black 5,3 group has 6 liberties.

If a stone/group is surrounded by enemy stones, in such a way that all of its liberties are blocked, the stone/group dies and the opposing player removes it/them from the board. In the image to the left the white stone is nearly surrounded. If black were to place one more stone at the point A the white stone would die. If white wishes to prevent this, she must play at A forming a white group with 3 unblocked liberties.

A dead stone that has been removed from the board is kept by the opponent. At the end of the game he counts each captured stone as one point.

Thus the game of Go has four objectives: (1) to surround territory, (2) reduce the opponents territory, (3) killing the opponents stones, (4) protecting your own stones from attack. The winner will inevitably be the player who has accomplished these goals more efficiently.

Instead of placing a stone on the board, a player may choose to pass and give the turn to the opponent without performing any action. This is typically done when a player can see that placing another stone will further none of the four goals above. The game ends when both players pass in succession.

The figure below shows how the board might look after a game has ended. Black has surrounded 9 points and white has surrounded 10 points. White wins by one point! If any stones where captured during play they would be added the respective players score. In the end game you may encounter neutral points such as the one marked by a cross. This point is not surrounded by any player and playing here will not kill any stones, thus the point is ignored.

For a more thorough introduction to the game you may download "The Way To Go" from: http://www.usgo.org/usa/waytogo/, and learn how to deal with stones that are "dead-on-the-board" and read about the "ko-rule".

Aditional information:
The British Go Association: http://www.britgo.org/
The American Go Association: http://www.usgo.org/
The Danish Go Association: http://www.danskgoforbund.dk/
The European Go Federation: http://www.eurogofed.org/