Hanezeki / Discussion

Sub-page of Hanezeki

unkx80: The following was the old contents on why hanezeki is a seki. Unfortunately, I found the presentation confusing, and so I decided to rewrite it.

Seki with strings in atari; Explanation why White cannot capture the stones

Hane seki - explanation  

tderz: W1 captures three stones, but also costs a liberty.
In semeais you prefer to start from the outside, resp. taking away the liberties from the other group.
However the left white+square inside the black group form a local seki, hence White is unable to start there.
Thus White puts herself at a disadvantage to start anywhere else than the preferred place (outside/other liberties).
This disadvantage continues after B2, as White cannot approach from the outside by a, as it would be suicide and create a life-enabling shape for Black.
White is forced to fill another (own) inside liberty -> b.

Hane seki - explanation  

tderz: Now, after Black B4, White is down to atari c,
but so is Black and thus has to remove the 3 white white+square before playing B4.

Hane seki - explanation  

tderz: After B4, White needs to play W5 in order to be able to kill,
however Black is able to play atari B6 and be 1 liberty ahead .

Herman Hiddema: More important is what happens if white does not play W3 in the above diagram!

Hane seki - explanation  

W3 pass, W5 pass

Herman Hiddema: Black continues by filling a liberty at B4, then capturing at B6. See the next diagram...

Hane seki - explanation  

Herman Hiddema: White has no option but to play W1, to keep the black group dead. This doesn't help however, as black now plays B2, putting the white group in atari.

The above diagrams are the true reason that neither player should capture in the original diagram. At the start, both players have a big eye. By capturing you remove your own big eye. See also BigEyeSmallEye

Hane seki - wrong starting position  

tderz: The position started as here and White had to find a way to survive (play h).

blubb: Why doesn't White play at the marked point? [1]

[1] Blubb is right, my starting diagram is worthless, it must be different.:

Hane seki - verification  

tderz: Replying to blubb's question Why not to capture at W1
After B2,

  • White has sente and 4 liberties (1 outside + 2 inside + 1 shared inside liberty = 4 in total),
  • Black only has 4 liberties (1 shared liberty + 3 inside liberties (5 for the yon-nakade are reduced to 3 as Black is forced to created sanmoku nakade by a necessary capturing move in gote) = 4 in total)
Hane seki - variation  

tderz: After W3 black B4 becomes necessary, as is W5.
Black loses by 1 liberty (2 : 3).

Hanezeki / Discussion last edited by Unkx80 on March 5, 2008 - 14:10
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