Big P

    Keywords: EndGame

The Big P is a corner shape that can be turned into a ko or a seki because of the special properties of the corner.

[Diagram]

Diagram

At first glance, Black seems to have 6 points of territory. However, after White plays a, Black can only get a seki or a ko. To prevent this, Black can turn the corner into 5 points of solid territory by playing a himself or either of the square points. (Playing at a is better, though, because White could get one ko threat against the corner if Black plays at either square.)


Black to make a ko

[Diagram]

Ko

If White gets to play W1, B2 and B4 turn the corner into a ko, and Black needs to find the first ko threat. This is less favorable unless Black is komaster.


Black to make a seki

[Diagram]

Seki

Black can make a seki in sente by playing B2. This is in most cases better than the making a ko of the position.


This is a copy of the living page "Big P" at Sensei's Library.
(OC) 2011 the Authors, published under the OpenContent License V1.0.
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