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A Japanese term describing an abstract concept in the game of Go (Wei Qi/Badouk). The literal translation is "frozen shape," but for purposes of Go, it is much more commonly referred to in English as overconcentration.

In Go, the eventual goal of the game is to stake out territory. To take territory, it will eventually become necessary to use one's stones to form an unbroken line around the territory, but this can mislead beginners about how one should go about this.

In fact, in the early stages of the game (fuseki and early chuban), it is very often to one's advantage to play as far as possible from other stones on the board (goban); playing too closely to the opponent's can bring one under attack, and playing too closely to one's own leads to korigatachi - overconcentration.

As an extreme example, consider the position on the goban below.

   a b c d e f g h j k l m n o p q r s t 
19 . . . . . . . . . . . . . . . . X . . 19
18 . . . . . . . . . . . . . . . . X . . 18
17 . . . . . . . . . . . . . . . . X . . 17
16 . . . + . . . . . + . . . . . + X . . 16
15 . . . . . . . . . . . . . . . . X X X 15
14 . . . . . . . . . . . . . . . . . . . 14
13 . . . . . . . . . . . . . . . . . . . 13
12 . . . . . . . . . . . . . . . . . . . 12
11 . . . . . . . . . . . . . . . . . . . 11
10 . . . + . . . . . + . . . . . + . . . 10
09 . . . . . . . . . . . . . . . . . . . 09
08 . . . . . . . . . . . . . . . . . . . 08
07 . . . . . . . . . . . . . . . . . . . 07
06 . . . . . . . . . . . . . . . . . . . 06
05 . . O . . . . . . . . . . . . . O . . 05
04 . . . + . . . . . + . . . . . + . . . 04
03 . . . O . . O . . O . . O . . O . . . 03
02 . . . . . . . . . . . . . . . . . . . 02
01 . . . . . . . . . . . . . . . . . . . 01
   a b c d e f g h j k l m n o p q r s t 

Anyone who has ever played Go will appreciate that the position above is completely absurd, but it serves to illustrate the principle. Both players have played seven stones on the goban. Black (X) has attempted to fence off territory with a solid wall. He has gained 8 points of unassailable territory in the top right. White (O) has played more efficiently, with two space jumps (niken tobi) along the third line (a formation which cannot be cut by the opponent, it turns out) and a keima shimari in each corner. It is not unreasonable for White to expect somewhere around 60 to 80 points on the lower side. White, then, has a nearly unsurmountable lead on Black (games of Go between good players tend to have margins of victory well under 10 points), just 12 moves into the game.

The above example was an extreme example, intended to illustrate the point in an unmistakable way. Sometimes, though, korigatachi can be more subtle, and more difficult to avoid. Imagine a situation like this:

   a b c d e f g h j k l m n o p q r s t 
19 . . . . . . . . . . . . . . . . . . . 19
18 . . . . . . . . . . . . . . . . . . . 18
17 . . . . . . . . . . . X . O . a O . . 17
16 . . . O . . . . . + . . . . . X b . . 16
15 . . . . . . . . . . . . . . . . . . . 15
14 . . . . . . . . . . . . . . . . . . . 14
13 . . . . . . . . . . . . . . . . . . . 13
12 . . . . . . . . . . . . . . . . . . . 12
11 . . . . . . . . . . . . . . . . . . . 11
10 . . . + . . . . . + . . . . . + . . . 10
09 . . . . . . . . . . . . . . . . X . . 09
08 . . . . . . . . . . . . . . . . . . . 08
07 . . . . . . . . . . . . . . . . . . . 07
06 . . . . . . . . . . . . . . . . . . . 06
05 . . . . . . . . . . . . . . . . . . . 05
04 . . . O . . . . . + . . . . . X . . . 04
03 . . . . . . . . . . . . . . . . . . . 03
02 . . . . . . . . . . . . . . . . . . . 02
01 . . . . . . . . . . . . . . . . . . . 01
   a b c d e f g h j k l m n o p q r s t 

White has just approached Q16 with a kakari at O17 - the standard way to approach a hoshi stone. Black responds with a very orthodox one-space low pincer at M17. White, seeking quick life, invades the corner at the san-san ("three-three") point R17. Black now has a choice of blocking at either "a" or "b". Shown below are the results of the usual joseki (standard corner pattern) for both blocks:

If Black blocks at "a":

   a b c d e f g h j k l m n o p q r s t 
19 . . . . . . . . . . . . . . . . . . . 19
18 . . . . . . . . . . . . . . X O O . . 18
17 . . . . . . . . . . . X . O X X O . . 17
16 . . . O . . . . . + . . . . . X O . . 16
15 . . . . . . . . . . . . . . . X . . . 15
14 . . . . . . . . . . . . . . . . O . . 14
13 . . . . . . . . . . . . . . . . . . . 13
12 . . . . . . . . . . . . . . . . . . . 12
11 . . . . . . . . . . . . . . . . . . . 11
10 . . . + . . . . . + . . . . . + . . . 10
09 . . . . . . . . . . . . . . . . X . . 09
08 . . . . . . . . . . . . . . . . . . . 08
07 . . . . . . . . . . . . . . . . . . . 07
06 . . . . . . . . . . . . . . . . . . . 06
05 . . . . . . . . . . . . . . . . . . . 05
04 . . . O . . . . . + . . . . . X . . . 04
03 . . . . . . . . . . . . . . . . . . . 03
02 . . . . . . . . . . . . . . . . . . . 02
01 . . . . . . . . . . . . . . . . . . . 01
   a b c d e f g h j k l m n o p q r s t 

If, on the other hand, Black blocks at "b":

   a b c d e f g h j k l m n o p q r s t 
19 . . . . . . . . . . . . . . . . . . . 19
18 . . . . . . . . . . . . . O . . . . . 18
17 . . . . . . . . . . . X . O . O O . . 17
16 . . . O . . . . . + . . . . X X X . . 16
15 . . . . . . . . . . . . X . . . . . . 15
14 . . . . . . . . . . . . . . . . . . . 14
13 . . . . . . . . . . . . . . . . . . . 13
12 . . . . . . . . . . . . . . . . . . . 12
11 . . . . . . . . . . . . . . . . . . . 11
10 . . . + . . . . . + . . . . . + . . . 10
09 . . . . . . . . . . . . . . . . X . . 09
08 . . . . . . . . . . . . . . . . . . . 08
07 . . . . . . . . . . . . . . . . . . . 07
06 . . . . . . . . . . . . . . . . . . . 06
05 . . . . . . . . . . . . . . . . . . . 05
04 . . . O . . . . . + . . . . . X . . . 04
03 . . . . . . . . . . . . . . . . . . . 03
02 . . . . . . . . . . . . . . . . . . . 02
01 . . . . . . . . . . . . . . . . . . . 01
   a b c d e f g h j k l m n o p q r s t 

Now, unless one has experience with Go, it is likely not easy to tell which position is more favorable for Black. One of the principles of Go is to try to cut apart your opponent's stones and keep your own connected. For this reason, many beginners would choose "a." It cuts off the original kakari stone (which will likely die, although it still has some aji), and keeps Black's pincer stone in close communication with his strong wall. However, this is the wrong strategy, because of the Black stone at R9.

When Black blocks at "b," White connects and makes life for his stones easily. Black, however, gets a good deal of "thickness" (meaning somewhat similar to "strength"). Another principle of Go, more important in this case than the idea of cutting and connecting, is that one should make wide extensions from a "thick" position. In this case, R9 is in a good position, and M17 limits White's potential for development along the top. In comparaison to this, the position resulting from Black "a" leaves M17 in a typical korigatachi situation, very overconcentrated. Meanwhile, White's stone at R14 somewhat reduces the usefulness of R9 (although R9 still has a positive effect Black's prospects in the lower right).

Once one begins to understand the principles of efficiency vs. overconcentration, a great deal of fuseki (opening) and early chuban (middle game) strategy revolves around trying to force one's opponent into korigatachi while avoiding it oneself.

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