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CarpenterSSquare

 

Shapes related to the carpenter's square
    Keywords: Life & Death

Please verify --Dieter

Shape 1

1. No outside liberties

[Diagram]
Shape 1

In addition, we will assume the marked stones, so as to give Black no escape routes to the outside. In this case, White can kill by playing the obvious placement at a.


[Diagram]
Killing placement

We will consider the following answers by Black: the hane of a, the descent of b and the perhaps less obvious placement of c.


[Diagram]
Var 1: hane

After W4, a and b are miai for the kill:


[Diagram]
Var 1.a

Black will eventually be forced to fill at a, after which his eyespace is almost filled with bent three. If White omits W2, Black gets at least seki by playing there


[Diagram]
Variation 1.b

Less intuitive perhaps is this variation. W2 makes an eye in the stomach. White will eventually be able to fill the inside liberties. If Black does so, his eyespace will become almost filled with a farmer's hat killing shape.


[Diagram]
Var 2.a: descent

In this variation, the outside liberties are important. Black puts up resistance, but White makes an eye in the stomach. She counts the inside liberties for a total of three. Black has only two outside liberties and falls short.


[Diagram]
Var 2.b: descent

If B3 here W4 falsens the eye.[1]


[Diagram]
Var 2.c: descent

If B3 here, W4 makes miai of a and b to either reduce Black's eyespace to three in a row or make an eye in the stomach with a farmer's hat shape.


[Diagram]
Var 3: placement

The cunning placement of B1 reverts to the above. W2 is again the key point.


[Diagram]
Var 3.b: mistake

If White connects with W4, B5 makes it a seki.


[Diagram]
Var 3.c: mistake

If W2 here, Black makes it ko.


[Diagram]
Var 3.d: mistake

W2 again leads to seki.



[1] Comments:

[Diagram]
Var 2.b: descent

Nope... after B7, a and 4 are miai.



2. Outside liberties

[Diagram]
Var 1: Alive

If Black has an extra liberty, this variation doesn't work anymore. Black lives through capturing a bent four.


[Diagram]
Var 2 : life

Same thing


[Diagram]
Var 3: ko

If B3 here, W4 now sets up a ko.


[Diagram]
Var 4: placement

The placement too works.


[Diagram]
Var 5: placement

As with this seki.



Shape 2

[Diagram]
Shape 2

This one looks alive. Any attempts ?



Matthew Woodcraft: I can't see a way to kill.

[Diagram]
Failed attempt 1

[Diagram]
Failed attempt 2

Charles Matthews I believe ko is the correct answer.


[Diagram]
Shape 2

unkx80: How about W1 and W3?



Authors



This is a copy of the living page "Shapes related to the carpenter's square" at Sensei's Library.
(OC) 2003 the Authors, published under the OpenContent License V1.0.