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KillingShape

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AlmostFill
LifeAndDeathTheBook
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UnsettledEyeshapes
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FarmerSHat
GuidedTours
AlmostAlmostFill
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Killing Shapes
Path: LifeAndDeath   · Prev: AlmostFill   · Next: SmallestGroupWithTwoEyes
PageType: Path     Keywords: Life & Death

Overview

[Diagram]
Killing shapes of stones



This board gives an overview of the basic killing shapes.

If the eyespace of a group is almost filled with one of the following shapes, it can be held to a single eye. If the surrounding stones are alive, it is dead.

Here they are again as spaces of marked points:

[Diagram]
Dead or killable eye shapes (1)



[Diagram]
Dead or killable eye shapes (2)



And this is how they will appear in games with a full border of black or white stones. If the border isn't complete the group has even less chance of life.

These are of course the same patterns three times over. The standard way to look at the shapes might be like this:

[Diagram]
Surrounded outside, too

Here it is completely clear what is meant: the vital point is at a and the black groups lives or dies according to whether Black can play there first.

The shapes, however, must be visualised in one or other way, to get answers about life and death questions. That may be long before the completed formations are in place on the board



Summary

[Diagram]
Basic dead shapes in a nutshell



This shape, a Greek cross, is the key killing shape, from which the others may be derived. The killing point to prevent two eyes (when these stones have been captured), is the center point WC. If you take away any other stone or stones from this shape you get another killing shape with the same killing point. In addition, if you add one stone to one of those shapes at a point (a) that is next to two of the arms of the cross, you also get a killing shape with the same killing point. (Some of these shapes have no unique killing point because the opponent cannot make two eyes with one move.)

You can learn more about these killing shapes at their separate pages:


Killing shapes

With these killing shapes, you can almost fill a wider range of killable eyeshapes.

Remarks

In the corner other killing shapes exist. The presence of cutting points also induces other killing shapes.


As per request on CoffeeMachine, I'll add a bit of information here for ease of reading. All of the above mentioned killing shapes have a vital point that can be exploited to kill any chance of two eyes. I will display them here. Many of these play out to be smaller shapes (for example, Five in a Cross often becomes Straight three or Bent three)

[Diagram]
Straight Three

[Diagram]
Bent Three

[Diagram]
Square Four

[Diagram]
Farmer's Hat

[Diagram]
Bulky Five

[Diagram]
Five in a Cross

[Diagram]
Rabbity Six


See also Nakade, Almost Fill and Eyespace.



Path: LifeAndDeath   · Prev: AlmostFill   · Next: SmallestGroupWithTwoEyes
This is a copy of the living page "Killing Shapes" at Sensei's Library.
(OC) 2003 the Authors, published under the OpenContent License V1.0.