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Good Empty Triangle
    Keywords: Shape

Efficiency is one aspect of shape. Late in the game, especially, it can be obviously correct to make an empty triangle and making an empty triangle can also be the vital point.

Example 1

[Diagram]
Joseki

B2 is the vital point, even though it is an empty triangle.


[Diagram]
Related joseki

B2 makes "good shape" but becomes overconcentrated.

unkx80: I don't think it's so much about overconcentration. I believe that it's got more to do with destroying White's eye shape.

Bill: Well, it is a question of emphasis, isn't it? Anyway, let's take away the BC stone.


[Diagram]
Mutual good shape

This is fine for both players, no? Black does not need an extra stone.



Example 2

[Diagram]
Black to play

This problem comes from the Tesuji Dictionary, by Segoe Kensaku and Go Seigen. They say that if you get this one right, you are 5 dan. (Of course, you have a big hint. ;-))

Solution



Example 3

[Diagram]
Good empty triangle

The sequence of W1 to W5 is one of the best ways of escaping with the lone white stone at the top. W5 makes the empty triangle and then White has a rather clear exit, while aiming for the cutting point at a (at the correct time).


[Diagram]
Bad empty triangle

W3 here would be a mistake. B4 plays at the vital point, destroying White's eye shape, and forcing W5 to connect with a bad empty triangle.



Cruncher: isn't this a Guzumi? I stumbled upon these pages, but they do not reference each other...

Tristan: You're right, Example 3 is certainly a guzumi. I'm not sure if guzumi refers to all good empty triangles or only the specific shape in Example 3, though. According to the discussion on guzumi, it may be a general term for makeshifts, but that discussion is not conclusive.



This is a copy of the living page "Good Empty Triangle" at Sensei's Library.
(OC) 2003 the Authors, published under the OpenContent License V1.0.