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LifeAndDeath

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BentFourInTheCorner
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Twisted four in the corner
Path: LifeAndDeath   · Prev: BentFourInTheCorner   · Next: RectangularSixInTheCorner
    Keywords: Life & Death

A twisted four which occurs in the corner may not be quite the same as the normal twisted four. The twisted four in the corner follows exactly the same logic as bent four in the corner.


1. Fewer than two outside liberties

[Diagram]
Fewer than two outside liberties

If there are fewer than two outside liberties, White can turn this position into a ko.


[Diagram]
Main line

White 3 starts the ko. White can finish the ko by filling at BC.



2. At least two outside liberties

[Diagram]
Two outside liberties

If there are at least two outside liberties, Black is alive with three points.


[Diagram]
Main line

Thanks to the two [circled point] liberties, Black can play atari at B4. Without one of those liberties, he would be putting himself into atari.



3. Endgame implications

[Diagram]
Main line

When White reduces the outside liberties with W1, B2 makes three points in gote, preventing the ko.

Side note: B2 at a also lives, but is inferior to B2 because White would have a ko threat at B2.



See also:


Authors



Path: LifeAndDeath   · Prev: BentFourInTheCorner   · Next: RectangularSixInTheCorner
This is a copy of the living page "Twisted four in the corner" at Sensei's Library.
(OC) 2004 the Authors, published under the OpenContent License V1.0.