Exploring the ancient board game of Go. See also my blog posts on Go.

## Intro

Go is an ancient oriental board game between two players where the objective is to capture territory. The typical physical set up is 181 black stones, 180 white stones, and a board with a 19x19 grid of 361 points or intersections. Smaller grids of 9x9 (81 points) and 13x13 (169 points) are also used for shorter games.

"Go" is the most common occidental name for the game: Go is called weiqi (围棋) in Chinese, go (碁) or igo (囲碁) in Japanese, and baduk (바둑) in Korean. One of the earlier references to Go is in the Analects of Confucius (ca 500 BCE), but the game has been referenced almost continuously in asian writings since then.

## Rules of Go

The rules of Go are simple. The rules of Go are the same every where with a few variants. I am restating the rules in my own words for the benefit of my own understanding. I have essentially combined from several sources.

For convenience, here is a one paragraph summary of the rules:

Black and white take turns placing stones at intersections on a board. Black goes first but white gets a bonus 0.5 points (komi) to avoid ties. Stones of the same color chain adjacently (vertically or horizontally). A chain must have at least 1 liberty (an adjacent empty intersection) to stay on the board. Ko rule: A placement is illegal if the resulting board state would be the same as the same player's previous turn. Two consecutive passes ends the game. Each controlled intersection is a point.

### Players and Equipment

Rule 1: Players. There are two players: Black and white. VARIANTS: Between players of equal levels it is arbitrary who gets which color. A random method like a coin toss could but used but in Japan nigiri ("grab") is used:

1. The senior player starts nigiri by grabbing some white stones without showing them.
2. The other player grabs one or two black stones to guess odd (kisuu-sen in Japanese) or even (guusu-sen in Japanese).
3. The senior player then reveals the grabbed stones.
4. If other player guessed correctly then he remains Black. Otherwise the players change colors.

Rule 2: Board. Aka Go ban (Japanese). The board has consists of a 19x19 grid (19 vertical and 19 horizontal lines) with 361 points or intersections between a vertical and horizontal line. VARIANTS: Non-official grids of different sizes are possible. For smaller or instructional games 9x9 grids (81 points) and 13x13 grids (169 points) are common. The 9 strategically important intersections, the star points (Hoshi in Japanese), are usually demarcated at 4 in and 10 in for 19x19 boards, at 4 in and 7 in for 13x13, and, 3 in and 5 in for 9x9.

Rule 3: Stones. Aka Go ishi (Japanese). Black uses black stones. White uses white stones. VARIANTS: Traditionally sets have 181 black stones and 180 white stones, but the point is to have enough stones to play.

Rule 4: Bowls. Aka Go ke (Japansee). Each player has a bowl for unplayed stones.

### Intersections

Rule 5: Occupation State. An intersections may be in 1 of 3 states of occupation:

1. Empty, i.e. unoccupied.
2. Occupied by a Black stone.
3. Occupied by a White stone.

Rule 6: Adjacent. Two intersections have an adjacent relationship if they are connected by a horizontal or vertical line and have no intersections between them.

Rule 7: Chains. A chain is one or more intersections of the same state whose members are adjacent.

Rule 8: Liberties. The number of liberties that a White or Black chain is its count of adjacent empty intersections. A chain with no liberties is "dead". A chain with liberties is "alive". A chain with 1 liberty is in "check" (atari in Japanese).

### Play

Rule 9: Initial Setup. The game begins with all intersections empty.

Rule 10: Turns. The Black player takes the first turn. Players alternate turns.

Rule 11: Turn Steps. The sequence of steps a player takes on their turn are as follows:

1. Pass or Not. If the player announces a pass, then the player's turn ends immediately. Otherwise proceed to the next step. VARIANTS: When a strong and weak player are matched, usually the stronger player goes with White and is handicapped by passing for 1 turn (a 2 stone handicap), or 2 turns (a 3 stone handicap), or more turns. Black usually starts by placing stones on the star points.
2. Place a Stone. Place a stone of his or her color on any empty intersection, unless it results in an illegal placement.
3. Capture. Remove from the board and set aside any dead chains of the opposing player.
4. Self-Capture. Remove from the board and return to the bowl any dead chains of the current player.

Rule 11: Prohibition of Repitition. Aka Ko Rule A placement is illegal if the resulting board state would be the same as the same player's previous turn. VARIANTS: Super ko prohibits the repetition of any previous board state.

Rule 12: Prohibition of Self-Capture. A placement is illegal if the result would only be self-capture. VARIANTS: Some rare variants (especially in Taiwan and New Zealand) allow self-capture.

Rule 13: Prohibition of Re-Placement. A placement is illegal if a stone is placed, let go, and then placed elsewhere in the same turn. VARIANTS: In official games, this may forfeit the game.

### End

Rule 14: End. The game ends when both players pass in consecutive turns. The final position is the board status at that point.

Rule 15: Win. The player with more points wins. There are various other was to lose not related to points, including the following: Resignation, forfeit by re-placing a stone, forfeit by not showing up for a match, forfeit by messing up the board, and forfeit by time control (byoyomi).

• Compensation Points. Aka Komi (Japanese); Deom (Korean). Since Black has an advantage of going first, official matches grant White extra points. The various Go organizations currently have komi ranging from 5.5 to 8. In handicap games komi is usually 0.5 points. A fraction (usually 0.5 points) is often part of komi to avoid a game with equal points (jigo in Japanese), i.e. to avoid draws (hikiwake in Japanese).
• Scoring System Points. There are several scoring systems, and they usually pick the same winner. Which scoring system is used only matters in very close matches and under which Go organization the game is played.
• Area Scoring (Chinese). "In the final position, an intersection is said to belong to a player's area if either: 1) it belongs to that player's territory; or 2) it is occupied by a stone of that player's color."
• Territory Scoring (Japanese and Korean). "In the final position, an empty intersection is said to belong to a player's territory if 1) all stones adjacent to it or to an empty intersection connected to it are of his color; and 2) there is at least one stone of his color."
• Territory/Area Scoring. A player's score is the count of intersections in their territory. Empty chains that are adjacent to two players (dame in Japanese) are not scored.
• Stone Scoring. A player's score is the number of stones on the board. Under stone scoring players usually play until their territories are filled up.

## ASCII Go

I wanted a very small, datbase-free visual way to represent Go, so I made ASCII Go. ASCII Go can be used in several ways: To write about Go, for kifu (game records), to play Go with a text editor, to play Go by email.

LEGEND:

o = White
x = Black
. = Intersection
* = Star Point


19x19 BOARD:

     0001 0002 0003 0004 0005 0006 0007 0008 0009 0010 0011 0012 0013 0014 0015 0016 0017 0018 0019
0001 .    .    .    .    .    .    .    .    .    .    .    .    .    .    .    .    .    .    .    0001
0002 .    .    .    .    .    .    .    .    .    .    .    .    .    .    .    .    .    .    .    0002
0003 .    .    .    .    .    .    .    .    .    .    .    .    .    .    .    .    .    .    .    0003
0004 .    .    .    *    .    .    .    .    .    *    .    .    .    .    .    *    .    .    .    0004
0005 .    .    .    .    .    .    .    .    .    .    .    .    .    .    .    .    .    .    .    0005
0006 .    .    .    .    .    .    .    .    .    .    .    .    .    .    .    .    .    .    .    0006
0007 .    .    .    .    .    .    .    .    .    .    .    .    .    .    .    .    .    .    .    0007
0008 .    .    .    .    .    .    .    .    .    .    .    .    .    .    .    .    .    .    .    0008
0009 .    .    .    .    .    .    .    .    .    .    .    .    .    .    .    .    .    .    .    0009
0010 .    .    .    *    .    .    .    .    .    *    .    .    .    .    .    *    .    .    .    0010
0011 .    .    .    .    .    .    .    .    .    .    .    .    .    .    .    .    .    .    .    0011
0012 .    .    .    .    .    .    .    .    .    .    .    .    .    .    .    .    .    .    .    0012
0013 .    .    .    .    .    .    .    .    .    .    .    .    .    .    .    .    .    .    .    0013
0014 .    .    .    .    .    .    .    .    .    .    .    .    .    .    .    .    .    .    .    0014
0015 .    .    .    .    .    .    .    .    .    .    .    .    .    .    .    .    .    .    .    0015
0016 .    .    .    *    .    .    .    .    .    *    .    .    .    .    .    *    .    .    .    0016
0017 .    .    .    .    .    .    .    .    .    .    .    .    .    .    .    .    .    .    .    0017
0018 .    .    .    .    .    .    .    .    .    .    .    .    .    .    .    .    .    .    .    0018
0019 .    .    .    .    .    .    .    .    .    .    .    .    .    .    .    .    .    .    .    0019
0001 0002 0003 0004 0005 0006 0007 0008 0009 0010 0011 0012 0013 0014 0015 0016 0017 0018 0019


Note that Go has no standard notation (like the algebraic notation of chess), but there are several notations and they all start with horizontal (from a player's view), then vertical.

• # (left-to-right), # (top-to-bottom). This is what I use in ASCII Go. EG: The 3 top star points are: (4, 4), (10, 4), and (16, 4).
• A-T (left-to-right, skipping I), 1-19 (bottom-to-top). EG: The 3 top star points are: D16, K16, Q16.
• #, # relative to a corner. EG: The 3 top star points are: (4, 4), (10, 4), and (4, 4).
• #, # relative to a named corner. EG: The 3 top star points are: A(4, 4), A(10, 4), and B(4, 4).

Here are some key board intersectins:

• Star points (hoshi):
• Origin of heaven (tengen): (10, 10)
• Corner star point: , (3
• (4, 4) if 19x19 or 13x13
• (3, 3) if 9x9
• Side star point: (10, 4) or (4, 10)
• 5 by 5 (go no go): (5, 5)
• Small eye (komoko): (4, 3) or (3, 4)
• High eye (takamoku): (5, 4) or (4, 5)
• Large high eye (otakamoku): (6, 4) or (4, 6)
• Outside the eye (mokuhazushi): (5, 3) or (3, 5)
• Outside the large eye (omokuhazushi): (6, 3) or (3, 6)

13x13 BOARD:

     0001 0002 0003 0004 0005 0006 0007 0008 0009 0010 0011 0012 0013
0001 .    .    .    .    .    .    .    .    .    .    .    .    .    0001
0002 .    .    .    .    .    .    .    .    .    .    .    .    .    0002
0003 .    .    .    .    .    .    .    .    .    .    .    .    .    0003
0004 .    .    .    *    .    .    *    .    .    *    .    .    .    0004
0005 .    .    .    .    .    .    .    .    .    .    .    .    .    0005
0006 .    .    .    .    .    .    .    .    .    .    .    .    .    0006
0007 .    .    .    *    .    .    *    .    .    *    .    .    .    0007
0008 .    .    .    .    .    .    .    .    .    .    .    .    .    0008
0009 .    .    .    .    .    .    .    .    .    .    .    .    .    0009
0010 .    .    .    *    .    .    *    .    .    *    .    .    .    0010
0011 .    .    .    .    .    .    .    .    .    .    .    .    .    0011
0012 .    .    .    .    .    .    .    .    .    .    .    .    .    0012
0013 .    .    .    .    .    .    .    .    .    .    .    .    .    0013
0001 0002 0003 0004 0005 0006 0007 0008 0009 0010 0011 0012 0013


9x9 BOARD:

     0001 0002 0003 0004 0005 0006 0007 0008 0009
0001 .    .    .    .    .    .    .    .    .    0001
0002 .    .    .    .    .    .    .    .    .    0002
0003 .    .    *    .    *    .    *    .    .    0003
0004 .    .    .    .    .    .    .    .    .    0004
0005 .    .    *    .    *    .    *    .    .    0005
0006 .    .    .    .    .    .    .    .    .    0006
0007 .    .    *    .    *    .    *    .    .    0007
0008 .    .    .    .    .    .    .    .    .    0008
0009 .    .    .    .    .    .    .    .    .    0009
0001 0002 0003 0004 0005 0006 0007 0008 0009


9x9 BOARD FOR DEMOS:

|   01 02 03 04 05 06 07 08 09 |
|01 .  .  .  .  .  .  .  .  .  |
|02 .  .  .  .  .  .  .  .  .  |
|03 .  .  *  .  *  .  *  .  .  |
|04 .  .  .  .  .  .  .  .  .  |
|05 .  .  *  .  *  .  *  .  .  |
|06 .  .  .  .  .  .  .  .  .  |
|07 .  .  *  .  *  .  *  .  .  |
|08 .  .  .  .  .  .  .  .  .  |
|09 .  .  .  .  .  .  .  .  .  |


7x7 BOARD FOR DEMOS:

| .  .  .  .  .  .  .  |
| .  .  .  .  .  .  .  |
| .  .  .  .  .  .  .  |
| .  .  .  .  .  .  .  |
| .  .  .  .  .  .  .  |
| .  .  .  .  .  .  .  |
| .  .  .  .  .  .  .  |


5x5 BOARD FOR DEMOS:

| .  .  .  .  .  |
| .  .  .  .  .  |
| .  .  .  .  .  |
| .  .  .  .  .  |
| .  .  .  .  .  |


## Tactics

Once you have the rules for Go you can discover the tactics by playing. In one sense you learn deeper if you discover the tactics through experience than through reading. Some of the tactics are so important that they are practically part of the rules. I will try to list tactics from easier to harder.

Much of Go is concerned with "life and death" problems (tsumego in Japanese), i.e. the determination of a group of stones into 1 of 3 statuses:

• Alive. A live group is one that is uncapturable, i.e. has 2 eyes or will inevitably have 2 eyes.
• Dead. A dead group is one that is capturable, i.e. does not have 2 eyes or will not inevitably have 2 eyes.
• Unsettled. An unsettled group is one that will be dead, alive, or mutualy alive (seki in Japanese) depending which player does what.

### Chaining/Connecting v Separating/Cutting

Placing stones 1 horizontal or vertical connection apart is a Skip (ikken shimari in Japanese) or One Space Jump (ikkien tobi in Japanese). Connecting a Skip is called a Pole Connection (botsugi in Japanese).

If Black connects at A, then Black will have 1 chain and White 2 chains.
| .  .  x  .  .  || .  .  x  .  .  |
| .  .  x  .  .  || .  .  x  .  .  |
| o  o  A  o  o  || o  o  x  o  o  |
| .  .  x  .  .  || .  .  x  .  .  |
| .  .  x  .  .  || .  .  x  .  .  |


Adjacent skips or bamboo joints (takefu in Japanese) are "unblockable" but it needs 4 stones:

In this 1st sequence White tries to block one way and fails:
| .  .  .  .  .  || .  .  .  .  .  || .  .  .  .  .  |
| .  .  x  x  .  || .  .  x  x  .  || .  .  x  x  .  |
| .  .  .  .  .  || .  .  .  o  .  || .  .  x  o  .  |
| .  .  x  x  .  || .  .  x  x  .  || .  .  x  x  .  |
| .  .  .  .  .  || .  .  .  .  .  || .  .  .  .  .  |

In this 2nd sequence White tries to block another way and fails:
| .  .  .  .  .  || .  .  .  .  .  || .  .  .  .  .  |
| .  .  x  x  .  || .  .  x  x  .  || .  .  x  x  .  |
| .  .  .  .  .  || .  .  o  .  .  || .  .  o  x  .  |
| .  .  x  x  .  || .  .  x  x  .  || .  .  x  x  .  |
| .  .  .  .  .  || .  .  .  .  .  || .  .  .  .  .  |


While you cannot directly chain diagonally, a Diagonal (kosumi in Japanese) is potentially "unblockable":

In this 1st sequence White tries to block one way and fails:
| x  .  .  .  .  || x  o  .  .  .  || x  o  .  .  .  |
| .  x  .  .  .  || .  x  .  .  .  || x  x  .  .  .  |
| .  .  .  .  .  || .  .  .  .  .  || .  .  .  .  .  |
| .  .  .  .  .  || .  .  .  .  .  || .  .  .  .  .  |
| .  .  .  .  .  || .  .  .  .  .  || .  .  .  .  .  |

In this 2nd sequence White tries to block another way and fails:
| x  .  .  .  .  || x  .  .  .  .  || x  x  .  .  .  |
| .  x  .  .  .  || o  x  .  .  .  || o  x  .  .  .  |
| .  .  .  .  .  || .  .  .  .  .  || .  .  .  .  .  |
| .  .  .  .  .  || .  .  .  .  .  || .  .  .  .  .  |
| .  .  .  .  .  || .  .  .  .  .  || .  .  .  .  .  |


Needlessly connecting a Diagonal form an Empty Triangle (akisankaku in Japanese) and is generally considered a bad shape for several reasons.

The 3 stone chain has 8 liberties.
| .  .  .  .  .  .  .  |
| .  .  o  o  o  .  .  |
| .  .  .  .  .  .  .  |
| .  o  .  .  .  .  .  |
| .  o  o  .  .  .  .  |
| .  .  .  .  .  .  .  |
| .  .  .  .  .  .  .  |
The 3 stone Empty Triangle only has 7 liberties.


Ponnuki frequent sequence when 3 stones in a L shaped diagonal (Tiger's Mouth or tora no kou in Japanese), the opponent plays in between, then is captured to form a Diamond.

  Tiger's Mouth       becomes a          Diamond
| .  .  .  .  .  || .  .  .  .  .  || .  .  .  .  .  |
| .  .  o  .  .  || .  .  o  .  .  || .  .  o  .  .  |
| .  o  .  .  .  || .  o  x  .  .  || .  o  .  o  .  |
| .  .  o  .  .  || .  .  o  .  .  || .  .  o  .  .  |
| .  .  .  .  .  || .  .  .  .  .  || .  .  .  .  .  |


A Knight's Move (keima or geima shimari in Japanese) is a set up for potential connection suggestive of a knight's move in chess.

| .  .  .  .  .  |
| .  .  .  x  .  |
| .  x  .  .  .  |
| .  .  .  .  .  |
| .  .  .  .  .  |


A Great Knight's Move (okeima or ogeima in Japanese) is also a set up for potential connection suggestive of a knight's move in chess.

| .  .  .  .  .  |
| .  .  .  .  x  |
| .  x  .  .  .  |
| .  .  .  .  .  |
| .  .  .  .  .  |


Immediate connection threats are concerned with "territory". More distant connection threats are concerned with "influence". The Knight and Great Knight are transitional between territory and influence. Other moves include Great Skips and Great Diagonal Moves.

If a player has an area with many stones or many connections or both, then the player has played "thick" in that area. If a player has an area with few stones or few connections or both, then the player has played "thin" in that area. Generally speaking you want to do the job as efficiently and thinly as possible, and avoid over-concentration and thickness. One measure of efficiency is the number of liberties per stones in the chain.

### Corners, Sides, and Center

It takes fewer stones to surround a corner than a side, and a side is easier to surround than a center.

     3 stones          5 stones          8 stones
| .  o  .  .  .  || .  .  .  .  .  || .  .  .  .  .  |
| o  o  .  .  .  || o  o  .  .  .  || .  o  o  o  .  |
| .  .  .  .  .  || .  o  .  .  .  || .  o  .  o  .  |
| .  .  .  o  o  || o  o  .  .  .  || .  o  o  o  .  |
| .  .  .  o  .  || .  .  .  .  .  || .  .  .  .  .  |


Since corners are advantageous, studies about the corners (joseki in Japanese, dingshi in Chinese, jungsuk in Korean) have been developed.

Here are 3 key corner shapes with 2 eyes. Although the smallest 2-eyed corner shape is only 2-3 lines out, opening moves are usually 3-5 lines out in order to get more territory.

        "W"               "C"               "F"
| .  .  .  .  .  || .  .  .  .  .  || .  .  .  .  .  |
| .  .  .  .  .  || .  .  .  .  .  || .  .  .  o  o  |
| .  .  .  o  o  || .  .  .  o  o  || .  .  .  o  .  |
| .  .  o  o  .  || .  .  o  .  o  || .  .  .  o  o  |
| .  .  o  .  o  || .  .  o  o  .  || .  .  .  o  .  |


### Eyes

An eye (me in Japanese) is an empty chain completely surrounded by a chain or chains of one color.

Black has 1 eye and can be captured:
| .  x  o  .  .  || o  x  o  .  .  || o  .  o  .  .  |
| x  x  o  .  .  || x  x  o  .  .  || .  .  o  .  .  |
| o  o  o  .  .  || o  o  o  .  .  || o  o  o  .  .  |
| .  .  .  .  .  || .  .  .  .  .  || .  .  .  .  .  |
| .  .  .  .  .  || .  .  .  .  .  || .  .  .  .  .  |


The "trick" is that if a shape has 2 eyes, then it cannot be captured!

Black has 2 chains forming 2 eyes and cannot be captured.
White cannot capture by playing either eye:
| x  .  x  o  .  |
| .  x  x  o  .  |
| x  x  o  .  .  |
| o  o  .  .  .  |
| .  .  .  .  .  |

Black has 1 chain forming 2 eyes and cannot be captured.
White cannot capture by playing either eye:
| x  x  o  .  .  |
| .  x  o  .  .  |
| x  x  o  .  .  |
| .  x  o  .  .  |
| x  x  o  .  .  |


Beware of false eyes (kageme in Japanese). They look like a pair of eyes but can actually be captured!

| .  x  o  .  .  || .  x  o  .  .  || .  x  o  .  .  |
| x  .  x  o  .  || x  o  x  o  .  || x  o  .  o  .  |
| o  x  x  o  .  || o  x  x  o  .  || o  .  .  o  .  |
| .  o  o  o  .  || .  o  o  o  .  || .  o  o  o  .  |
| .  .  .  .  .  || .  .  .  .  .  || .  .  .  .  .  |


### Polyominos

Polyominos [W] are plane geometric figures formed by joining one or more equal squares edge to edge. Polyominos come up a lot in Go, especially as eyes.

Monomino. An eye of 1 intersection is a monomino.

Domino. An eye of 2 intersections is a dominio. These are common in Ko fights.

Tromino. These are I or L shaped and are unsettled. Whoever gets the middle wins!

Tetromino. These are the 7 Tetris shapes.

Tetromino O. Dead.
| .  .  x  o  .  |
| .  .  x  o  .  |
| x  x  x  o  .  |
| o  o  o  o  .  |
| .  .  .  .  .  |

Tetromino T. Unsettled. Whoever gets the middle (A) wins!
| x  x  x  x  x  |
| x  .  A  .  x  |
| x  x  .  x  x  |
| o  o  x  o  o  |
| .  o  o  o  .  |

The other tetrominos (I, L, J, S, Z) are alive.


Pentomino. There are 12.

Pentomino P. Unsettled. Whoever gets the middle (A) wins!
| x  x  x  x  x  |
| x  .  A  .  x  |
| x  x  .  .  x  |
| o  o  x  o  o  |
| .  o  o  o  .  |

Pentomino X. Unsettled. Whoever gets the middle (A) wins!
| x  x  .  x  x  |
| x  .  A  .  x  |
| x  x  .  x  x  |
| o  o  x  o  o  |
| .  o  o  o  .  |

The other pentominos (F, I, L, N, T, U, V, W, Y, Z) are alive.


Hexomino. There are 35.

Hexomino fish. Unsettled. Whoever gets the middle (A) wins!
| x  x  .  x  x  |
| x  .  A  .  x  |
| x  x  .  .  x  |
| o  o  x  o  o  |
| .  o  o  o  .  |

The other hexomoinos are alive.


Heptomino and above. Alive but the defender must still be careful.

### Mutual Life (Seki)

A Mutual Life (seki in Japanse) is a situation where logically neither player would act to push the area to life or death since doing so would be a loss. Such areas are not scored (dame in Japanese). Beginners commonly get rid of seki for a net loss, when it would have been better to leave the stones "alive in seki". There are many possible seki scenarios, I will only show a few.

| x  o  .  x  o  |
| x  o  .  x  o  |
| x  o  x  x  o  |
| x  x  o  o  o  |
| .  .  .  .  .  |

| .  .  .  .  .  .  .  |
| .  .  .  .  .  .  .  |
| o  o  o  o  .  .  .  |
| x  x  x  x  o  .  .  |
| x  o  .  x  o  .  .  |
| o  o  .  x  o  .  .  |
| .  x  x  o  o  .  .  |


A Ladder Attack (shicho in Japanese, "a running attack") is a sequence of Turns (hane in Japanese) where one player tries to escape out of atari. The ladder attack usually succeeds unless the sequence eventually connects to another chain which breaks atari. The breaker is a stone of refuge (shicho atari in Japanese).

Here are 2 ladder attacks. Black will be able to escape on the diagonal one because it would eventually connect to the shicho atari (xA at 6, 6). White will not be able to escape the vertical one.

|   01 02 03 04 05 06 07 08 09 |
|01 .  o  .  .  .  .  .  .  .  |
|02 o  x  o  .  .  .  .  x  x  |
|03 o  x1 x3 o4 *  .  *  x  o  |
|04 .  o2 x5 x7 .  .  .  x  o  |
|05 .  .  o6 .  *  .  *  x  o  |
|06 .  .  .  .  .  xA .  .  .  |
|07 .  .  *  .  *  .  *  .  .  |
|08 .  .  .  .  .  .  .  .  .  |
|09 .  .  .  .  .  .  .  .  .  |


### Net or Cap Blocks (Geta)

A Net or Capping Block (geta in Japanese) is loosely surrounding an enemy stone in such a fashion that the enemy cannot escape.

Here are 4 attempted net blocks. All should succeed except for the last.
| x  .  .  .  .  || x  .  .  .  .  || x  x  .  .  .  || x  .  .  .  .  |
| .  o1 .  .  .  || x  .  .  .  .  || x  x  .  .  .  || x  x2 .  .  .  |
| .  .  .  .  .  || .  o1 .  .  .  || .  .  o1 .  .  || x  .  .  .  .  |
| .  .  .  .  .  || .  .  .  .  .  || .  .  .  .  .  || .  o1 .  .  .  |
| .  .  .  .  .  || .  .  .  .  .  || .  .  .  .  .  || .  .  .  .  .  |


### Snapback or Sacrifice Play (Uttegae)

A Snapback or Sacrifice Play (uttegae in Japanese) is a two-step tactic that involves a player making an initial loss for a greater gain. Such opportunities are harder to spot than tactics shown so far, and may require reading ahead, but sacrifices may also arise naturally from simply defending or spotting dead stones.

Black blocks the connection and threatens the White stones.
This stone will be the sacrifice.
|   01 02 03 04 05 06 07 08 09 |
|01 .  x  .  .  .  .  .  .  .  |
|02 x  o  x  .  .  .  .  .  .  |
|03 .  o  x  .  *  .  *  .  .  |
|04 x1 o  x  .  .  .  .  .  .  |
|05 o  x  x  .  *  .  *  .  .  |
|06 o  o  o  .  .  .  .  .  .  |
|07 .  .  *  .  *  .  *  .  .  |
|08 .  .  .  .  .  .  .  .  .  |
|09 .  .  .  .  .  .  .  .  .  |

White reacts by capturing the Black stone,
especially since his stones are dead.
|   01 02 03 04 05 06 07 08 09 |
|01 .  x  .  .  .  .  .  .  .  |
|02 x  o  x  .  .  .  .  .  .  |
|03 o2 o  x  .  *  .  *  .  .  |
|04 .  o  x  .  .  .  .  .  .  |
|05 o  x  x  .  *  .  *  .  .  |
|06 o  o  o  .  .  .  .  .  .  |
|07 .  .  *  .  *  .  *  .  .  |
|08 .  .  .  .  .  .  .  .  .  |
|09 .  .  .  .  .  .  .  .  .  |

Black snapbacks and captures the other White stones.
|   01 02 03 04 05 06 07 08 09 |
|01 .  x  .  .  .  .  .  .  .  |
|02 x  .  x  .  .  .  .  .  .  |
|03 .  .  x  .  *  .  *  .  .  |
|04 x3 .  x  .  .  .  .  .  .  |
|05 o  x  x  .  *  .  *  .  .  |
|06 o  o  o  .  .  .  .  .  .  |
|07 .  .  *  .  *  .  *  .  .  |
|08 .  .  .  .  .  .  .  .  .  |
|09 .  .  .  .  .  .  .  .  .  |

Same start but now Black plays badly and does not block.
|   01 02 03 04 05 06 07 08 09 |
|01 .  x  .  .  .  .  .  .  .  |
|02 x  o  x  .  .  .  .  .  .  |
|03 x1 o  x  .  *  .  *  .  .  |
|04 .  o  x  .  .  .  .  .  .  |
|05 o  x  x  .  *  .  *  .  .  |
|06 o  o  o  .  .  .  .  .  .  |
|07 .  .  *  .  *  .  *  .  .  |
|08 .  .  .  .  .  .  .  .  .  |
|09 .  .  .  .  .  .  .  .  .  |

White connects and threatens Black.
|   01 02 03 04 05 06 07 08 09 |
|01 .  x  .  .  .  .  .  .  .  |
|02 x  o  x  .  .  .  .  .  .  |
|03 x1 o  x  .  *  .  *  .  .  |
|04 o2 o  x  .  .  .  .  .  .  |
|05 o  x  x  .  *  .  *  .  .  |
|06 o  o  o  .  .  .  .  .  .  |
|07 .  .  *  .  *  .  *  .  .  |
|08 .  .  .  .  .  .  .  .  .  |
|09 .  .  .  .  .  .  .  .  .  |

Black tries to save but the corner stones are captured.
|   01 02 03 04 05 06 07 08 09 |
|01 x3 x  o4 .  .  .  .  .  .  |
|02 x  o  x  .  .  .  .  .  .  |
|03 x1 o  x  .  *  .  *  .  .  |
|04 o2 o  x  .  .  .  .  .  .  |
|05 o  x  x  .  *  .  *  .  .  |
|06 o  o  o  .  .  .  .  .  .  |
|07 .  .  *  .  *  .  *  .  .  |
|08 .  .  .  .  .  .  .  .  .  |
|09 .  .  .  .  .  .  .  .  .  |

(This example is right out of Go Fundamentals but with the orientations clarified.)


## Strategy

Once you have the rules for Go you can discover the strategy by playing. In one sense you learn deeper if you discover the strategy through experience than through reading.

• In general go for the corners, then the sides, then the center.
• Corner strategies (joseki in Japanese, dingshi in Chinese) often initiate with a placement at a point 3 and 4 lines in (komoku in Japanese), but variants such as 3-3, 3,5, 4-4, etc., are possible.
• Balance local territory tactics against board-wide strategy such as loosely influencing general areas.

Here are more basic strategies pulled right out of Wikipedia. Some of them are so concise, that I don't see a need to rewrite them.

• Connection: Keeping one's own stones connected means that fewer groups need to make living shape, and one has fewer groups to defend.
• Cut: Keeping opposing stones disconnected means that the opponent needs to defend and make living shape for more groups.
• Stay alive: The simplest way to stay alive is to establish a foothold in the corner or along one of the sides. At a minimum, a group must have two eyes (separate open points) to be "alive." An opponent cannot fill in either eye, as any such move is suicidal and prohibited in the rules.
• Mutual life (seki) is better than dying: A situation in which neither player can play to a particular point without then allowing the other player to play at another point to capture. The most common example is that of adjacent groups that share their last few liberties—if either player plays in the shared liberties, they can reduce their own group to a single liberty (putting themselves in atari), allowing their opponent to capture it on the next move.
• Death: A group that lacks living shape, meaning less than two eyes is eventually removed from the board as captured.
• Invasion: Set up a new living group inside an area where the opponent has greater influence, means one reduces the opponents score in proportion to the area one occupies.
• Reduction: Placing a stone far enough into the opponent's area of influence to reduce the amount of territory they eventually get, but not so far in that it can be cut off from friendly stones outside.
• Sente: A play that forces one's opponent to respond (gote), such as placing an opponent's group in atari (immediate danger of capture). A player who can regularly play sente has the initiative, as in chess, and can control the flow of the game. [I love this aspect, very martial. Japanese martial arts has lots of sen. The German Liechtenauer school also discusses timing with its Vor, Indes, und Nach = "Before, During, and After".]
• Sacrifice: Allowing a group to die in order to carry out a play, or plan, in a more important area.

## References

• Beginning Go (2008) by Shotwell, Peter and Long, Susan.
• Go Fundamentals (2009) by Kishikawa, Shigemi. I do not like that sometimes when he would show a series of moves, one or more of the groups would be rotated. Also my printed copy had 3 chapters duplicated!
• The Rules and Elements of Go (1977) by Davies, James.

### Go Equipment

Traditional Japanese boards (goban) can go for as much as \$60,000 especially when made from 700 year old coniferous kaya tree (torreya nucifera), aka "genuine kaya" (hon kaya), and dried for 15 years, and the lines are carved in with a sword. Hyuga kaya is hon kaya from the Hyuga region (now the Miyazaki prefecture). "New kaya" (shin kaya) is "faux kaya" and not biologically related to hon kaya. Traditional Japanese stones (goishi) are made of clamshell (white) and slate (black), with historical pieces made of jade. Chinese stones from Yunnan China are called yunzi, and come in single-convex or double-convex (like Japanese stones). Larger stones are more expensive than smaller stones.

### Miscellany

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