Diagonal play reference shapes

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Theory of the diagonal contact position

This pattern is one of the most-frequently discussed of simple configurations on SL.

A much-discussed shape  

This shape would usually arise from a diagonal contact sequence.

Diagonal contact by White  

Since W1 very often forces B2, it is a popular play in many contexts. But not always a good one.

The point is that W1 isn't now a well-placed stone.


We can make these comparison shapes, in which white+circle has been moved from a, or white+square moved from b. Obviously in these cases Black and White have equal influence. Therefore in the diagonal contact shape White has less than 50% of the influence: the diagonal contact stone seems to be on the 'inside', or to overlap too much with White's initial stone.

Extending the other way

Diagonal contact by White  

Suppose B2 is played. This idea comes in a number of joseki.

On the bulge point  

Now white+circle occupies an important bulge point: White has achieved good shape instead.

Towards eye shape

Another fundamental way of thinking is the diagonal as half-way to an eye.

Future eyes?  

White could hope to build an eye with the two circled points here, or the two square-marked points.

No prospect  

If either of the black+circle and black+square stones is in position, White's eye shape is much worse. If both black stones are there, this looks like a pattern with Black on the attack. White's plays at the marked points are now bad shape.

The page diagonal attachment - as inferior shape discusses further the first of these topics, and compromised diagonal the second.

The Japanese term hebo kosumi may well refer to both shapes, made inappropriately.


Diagonal contact pattern

Compromising the diagonal

Charles Matthews

Diagonal play reference shapes last edited by CharlesMatthews on June 6, 2003 - 11:47
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