How To Play Go Baduk Weiqi and Igo

Much like chess, Go is a two player game with a special board and set of playing pieces.

The Board

The board consists of a grid of lines, whose size is specified by counting the number of intersections, including the ones on the edges. Commonly used sizes are 9x9, 13x13, and 19x19.

The standard board size is 19x19. However, players start out playing on 9x9 because a 19x19 is too much to think about when you're still struggling with the rules.

The Stones

In Go, each player receives a set of stones. There are 180 white stones and 181 black stones in a go set, which is enough to cover the entirety of a 19x19 board. If you are counting the score using Chinese rules, then it is essential to have the right number of stones (or at least to know precisely how many of each color you have). If you are using Japanese rules, then it is only necessary to have enough stones to play the game. If you are playing on a smaller board, you need proportionally fewer stones.

All of the stones are identical, except for the difference in color between two sets of stones.

Placing the Stones on the Board

As you may have guessed from the way that the board sizes are indicated, the stones are placed on the intersections of the lines, not in the squares.

While this seems odd from the occidental point of view (chess, checkers, etc), another oriental board game, Chinese chess, also places it's pieces on the intersections of the lines.

To begin the game: The person using the black stones goes first. (this gives them an advantage).

Who Goes First?

The person using the black stones, often referred to simply as "Black", goes first.. Because going first confers an advantage, the weaker player generally plays with the black stones.

What Do You Do On Your Turn?

You play one stone of your own color. You may play your stone on any intersection of the board.

There are two reasons that would forbid you from placing a stone at a particular intersection:

• Suicide
  If placing your stone there would cause one or more of your own stones to be removed from the board immediately, you may not play there.
  
• Ko
  If playing there causes the board to be identical to what it was at the end of your previous move, you may not play there. I'll explain this with examples momentarily.
  

Once they are placed on the board, the stones are not moved. They are removed if they are captured by the opposing player.

When Do We Stop Playing?

When a player believes that there are not more profitable moves to make, they can pass their turn. If both players pass on consecutive moves, then the game ends and it is time to count up the score.

When you pass, you do not play a stone. Instead, you simply tell your opponent "I pass."

So, Who Won?
Counting the Score: Where's My Territory?

Each player gets one point for each intersection of open (unoccupied by stones) territory that she controls. "Controlling" territory means that you have surrounded it with a wall (a line) of your stones.

Dead Stones

If the other player has stones in your territory, both players must agree that they are "dead" (I'll explain in a moment what that means). Then those stones are treated as if they were captured during the game.

The captured stones are placed back on the board during counting, inside their player's territory.

Simplifying Counting

Stones inside the walls of your territory can be rearranged to make it easier to count, as long as you are careful not to move the boundaries of your territory. If you are unsure whether a particular way of rearranging the stones is okay, you can test it by counting the territory before you move them and then again after moving the stones around. If the sum stays the same, then that manoeuvre is fine (and you can use it to save time counting in the future).

The winner is the person with more points.
If there is a tie, then white wins, since black got the advantage of going first.

When a stone is placed on the intersection of a pair of lines, there are four lines coming out of it. The four other intersections connected to the stone by these four lines are its "liberties".

If your opponent's stones occupy all of your stone's liberties, you stone is captured.

The same rule holds true for a group of stones.
If another stone of yours occupies one of your stone's liberties, they form a small group. Stones become "firmly connected" and part of the same group if they are in each others liberties.
A line of stones, each connected to two other stones (except for the ends, which are only connect to one), form a group.

The liberties of a group are the liberties of its member stones that are not occupied by other members of the group.
For example, a group of two stones has six liberties.

If your opponent's stones occupy all the liberties of a group, then that group has been captured and all the stones in the group are removed from the board.

If playing there causes the board to be identical to what it was at the end of your previous move, you may not play there.

This most often occurs when you capture one of you opponents stones, but in capturing that stone, you put one of your stones in atari. (Atari means that your stone or group of stones only has one liberty left - you opponent can play just one stone and capture it).

In this case, you opponent cannot immediately capture your atari stone because then the board would look exactly the same as it did before. The reason that having the board look exactly the same is that, since we assume that you made the correct move before, then you'll make the same move. Then, they'll make the same more. And so on -- An Infinite Loop.

Obviously, this isn't any fun to get stuck in. So we don't even let that get started.

Your atari stone isn't safe for ever. On your opponents next turn (after he plays once and you play once), he can take you stone. Since two more stones (or at least one, if one of you passed) have been played, the board is different -- so it won't be exactly the same.

What is takes to be alive is two eyes. (Groups that do not explicitly have two eyes, but are alive, have room to form those eyes if your opponent forces you to).

This poster shows the smallest live groups in the corner, on the side, and in the middle of the board.

By observing the number of stones that each group requires, you can see why the corner is the easiest place to live, the next easiest the side, and the middle of the board is the hardest place to form a live group.
When you take into account that each stone in a group represents one of your turns (and there fore an opportunity for your opponent to make things difficult on his turn), it is clear that taking the fewest number of stones makes a group the easiest to form.

If you stones are alive, it means that if you opponent were to try to capture them, you could prevent him from doing so.

At the end of the game, if one of your stones is inside your opponent's territory, then it is dead because you decided it would not be able to make the 'eyes' or the connection to an already living group that it would need to survive. If you thought that it could live, then you would have played a stone necessary to making it into a live group rather than passing.