Shapes Related To The Carpenters Square / Version 20090527

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.

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.

Var 1: hane  

After , a and b are miai for the kill:

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 , Black gets at least seki by playing there

Variation 1.b  

Less intuitive perhaps is this variation. 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 pyramid four killing shape.

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.

Var 2.b: descent  

If here falsens the eye.^[1]

Var 2.c: descent  

If here, 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 pyramid four shape.

Var 3: placement  

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

Var 3.b: mistake  

If White connects with , makes it a seki.

Var 3.c: mistake  

If here, Black makes it ko.

Var 3.d: mistake  

again leads to seki.

Var 2.b: descent  

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

Var 1: Alive  

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

Var 2 : life  

Same thing

Var 3: ko  

If here, now sets up a ko.

Var 4: placement  

The placement too works.

Var 5: placement  

As with this seki.

Shape 2  

This one looks alive. Any attempts ?

Failed attempt 2  

Charles Matthews I believe ko is the correct answer.

Shape 2  

unkx80: How about and ?

If black has outside liberties, white can still get a ko  

pitimp?: if black playes 4 at "a", white 5 at "b" is still ko