Basic living eye shapes

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The discussions on living eye shapes by default assume that the group surrounding the empty points is a single chain, i.e., there are no cutting points. In some cases, the status of a surrounded group with a particular eye shape alters if that group contains cutting points.

Four-point eye shapes

In general there are five different four-point eye-shapes. Three of them, the straight four, the bent four and the twisted four are living shapes (no further play necessary). The status of the pyramid four depends on sente and the squared four (tombstone) is dead as it stands. Bent four in the corner and twisted four in the corner are a special case, which may be dead or alive depending upon outside liberties.

[Diagram]

Straight four

In the straight four, B1 and W2 in the diagram are miai.


Five-point eye shapes

All five-point eye shapes are alive except the crossed five and the bulky five. Some examples:

[Diagram]

A five-point shape that is alive

[Diagram]

Another five-point shape that is alive


Six-point eye shapes

All six-point eye shapes (including rectangular six) are unconditionally alive except for the rabbitty six. An exception is rectangular six in the corner, whose status depends on the number of external liberties -- zero liberties is dead, one outside liberty results in ko, and two outside liberties is unconditionally alive.


Seven-points eye shapes

All eye shapes of seven points are alive.

[Diagram]

Seven lives

This shape (butterfly seven) is one that seems most likely to be killed, but after B1 the position is seki.


orangeblood?: How do we define "alive" here? There are seven-point shapes other than the bulky seven that can live only after a ko. An example is the Walkie Talkie Seven. [ext] http://senseis.xmp.net/?WalkieTalkieSeven

RobertJasiek: Why would you want to define "alive" differently from the [ext] general definitions?

Bass: "Alive" in the context of life and death analysis means "alive with points or alive in seki". Also, the rule of thumb ("a seven point eye lives") only applies to seven point eye shapes in the center, when there are no cutting points in the shape.

RobertJasiek: Both (general definitions and context of life + death analysis) are correct.

orangeblood?: This points to the confusion I'm talking about. Wondering if my 7-point shape was OK, I Googled and hit this page and saw that all 7-point shapes (excepting the one, which mine was not) are alive. Then, I find out that it's only alive if I win a ko battle. I'm not complaining at all, just saying this could be a bit clearer.

Eight-points eye shapes

All Eight-point eye shapes are unconditionally alive but for those that result in Ten Thousand Year Ko. There are at least two Ten Thousand Year Ko shapes.

[Diagram]

corner: after 1 and 2, W lives with TenThousandYearKo (Mannen Ko) -- see below

[Diagram]

The TenThousandYearKo (Mannen Ko) revealed

[Diagram]

Another TenThousandYearKo (Mannen Ko) -- The Long L Group


Damien Sullivan All this is good, but I've had interest in minimal living shapes which aren't fully surrounded yet and may be peeped at. Assumptions: group is trying to live in place, not run away; all cuts work for white.

[Diagram]

corner ponnuki lives

Black's ponnuki in the corner is alive, though it will have to respond to descents.

[Diagram]

offset corner ponnuki

is I think immune to attack.

[Diagram]

side life

On the side a ponnuki needs two more stones; peeps will cause it to form one of the 8-stone shapes.

[Diagram]

19x19 diagram

Black is alive with 7. The finished form will have 11 stones, not the 10 of a minimal form. The white group is not nearly as safe as my beginning intuition suggested, without a defensive stone at a.


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This is a copy of the living page "Basic living eye shapes" at Sensei's Library.
(OC) 2012 the Authors, published under the OpenContent License V1.0.
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