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L+1 group
Path: LifeAndDeath   · Prev: LGroup   · Next: LongLGroup
    Keywords: Life & Death

An L+1 group is an L group with a leg. The leg can be at the short side or the long side of the L shape. In both cases the group lives or dies according to who has sente.


First L+1 Group

[Diagram]
First L+1 group

The first L+1 group lives or dies according to who has sente.


[Diagram]
Black lives

Black can live by playing on the 1-2 point as shown.


[Diagram]
White kills

White can kill by playing hane at 1. This reduces the shape to the standard L group, which we already know is dead.



Second L+1 Group

[Diagram]
Second L+1 group

If the leg is on the other side, again the position depends on who has sente.


[Diagram]
Black lives 1

Now the 2-2 point is the vital point for Black.


[Diagram]
Black lives 2

Erock: Can Black also live by playing the 1-2 point?


[Diagram]
Black gives white an extra ko threat

Answer to Erock: Jared Beck: In "Black lives 1" black lives, and white has 3 ko threats for a later time. In "Black lives 2" black also lives, but white has 4 ko threats.


[Diagram]
Or Black loses a couple points

Jared Beck: If Black chooses to give up a few points, he doesn't have to suffer the burden of a fourth ko threat.

Jared Beck: Please double-check this, I just looked at it briefly.


[Diagram]
White kills

Again, reducing Black to a basic L group by a hane, kills the corner.



Second L+1 Group, weak leg

[Diagram]
Second L+1 group

The second L+1 group with a weak leg is also unsettled. White can kill at a or Black can live by playing at a.


Second L+1-group, hane

[Diagram]
Problem

The extra hane gives some degree of security. The squared stone provides an outward escape.


[Diagram]
Problem

The throw-in at W1 doesn't work anymore. Black forces with B2 and lives with B4: White can not connect at a because Black can capture three to make an eye.

unkx80: Comment: The exchange of B2 and W3 is not neccessary.


[Diagram]
Problem

The attachment at W1 leads to ko.





Third L+1 Group?


[Diagram]
Third L+1 Group??

Hikaru79 Assuming it's White's play next, can this shape be killed?

No. Only if there are white stones at a and b, White can kill with Wc, Bd, We.


[Diagram]
B2 tenuki

Joonas Tyystjärvi: I'm quite probably missing something here, but I don't think white has even a ko threat here. After B10, a and b are miai for black, and this looks like fairly silly endgame.

ChrisSchack: I'd be more inclined to call this a J+1 group or something, take a look at the J Group...



Path: LifeAndDeath   · Prev: LGroup   · Next: LongLGroup
This is a copy of the living page "L+1 group" at Sensei's Library.
(OC) 2004 the Authors, published under the OpenContent License V1.0.