:: Igo Hatsuyôron 120 (2021)

Variations of Our Solution (IIIb)

Tricking KataGo (Triple-Ko)

VAR (C) (A) (.2) (.1) (.2)

: ( 222aw)
White plays the central attachment in the left centre.

:
Black ignores White's last move and captured for another time in the upper right.

Alternatively, he might consider answering White's move in the left centre by connecting at . This would result in the "usual" score of Black + 5 in the Semeai Variation, as in the alternative subvariations, because White also lost one move here just before.

:
White decides to establish two points of territory in the left centre.

:
Black simply continues at the left, occupying White's liberties there.
He is well aware that White lost two tempi in the Main Semeai by her manoeuvre.

He might consider continuing with , or , in the upper right corner, but he will not really benefit by these moves.
Connecting at would be possible now, but benefit White in the Semeai Variation, so losing one point overall unnecessarily.

:
White has to block - sooner or later.

:
White captures in the upper right corner.

:
White captures for another time in the upper right.

She might consider connecting at , instead, losing another tempo in the Main Semeai.
Thereafter, Black would be able to save his large group in the upper right in the Semeai Variation (he had ten Main Semeai Liberties then), but White would not lose a point in the Capture Variation, compared to the superordinate variation.


Ko: ;

:
Black recaptures the ko in the upper right.

:
Black captures again in the upper right.

This proves that White could have done without capturing Black's stones in the upper right first, if she wanted to choose this line.

:
This is the moment of White's decision point.

In the Capture Variation, she will use her sente after the dissolving of the hanezeki to capture at . Black will connect at and White will also connect.

Capture Variation:

Compared to the superordinate variation ...

  • White got an additional two points of territory in the left centre.
  • White got two points of territory less in the upper right corner.
  • Black captured an additional White stone in that area.

In total, White lost one point.

Black + 2 => Black + 3

///:

Semeai Variation:

:
White captures in the upper right.

:
Black connects the hanezeki's tail.

:
White plays oki in the lower right, of course.

; :
Both sides continue with occupying opponent's liberties.

...

:
Black captures White's group in the lower right corner.

:
White has to capture the ko in the upper right, so giving atari at Black's large group.

:
Black uses this atari at White's four stones at the upper edge as a ko threat.

:
White captures.

She is unable to answer Black's ko threat, e.g. by connecting at .
Black would recapture the ko and give atari with thereafter, so bringing his large group at the right to life.

:
Black captures at the top.

:
White has to connect.

Semeai Variation:

Compared to the superordinate variation ...

  • White got an additional two points of territory in the left centre.
  • Black's cumulated gain at the top is eleven points.
  • In the upper right corner, White captured an additional Black stone, but lost one point of territory, so the net effect is zero.

In total, White lost nine points.

Black + 5 => Black + 14

Copyright © 2021 Thomas Redecker.

Design by Jan van Rongen, modified by Thomas Redecker.

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