L+1 group

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  Difficulty: Intermediate   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.

Table of contents Table of diagrams
First L+1 group
Black lives
White kills
First L+1 group, hane on one side
White cannot kill this way
White kills
Second L+1 group
Black lives
White kills
Second L+1-group, hane one side
White cannot kill this way
White kills
Problem
Problem
Second L+1 group


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 W1. This reduces the shape to the standard L group, which we already know is dead.


First L+1 group, hane on one side

[Diagram]

First L+1 group, hane on one side

The extra hane gives some degree of security.

[Diagram]

White cannot kill this way

The throw-in at W1 no longer works: B2 jumps and lives. If W3 makes a placement, B4 connects, and White cannot connect at a due to shortage of liberties, otherwise Black captures three to make an eye.

[Diagram]

White kills

However, White can kill by the hane at W1 followed by the placement at W3. B4 tries to live, but W5 forces B6, so W7 makes a throw in and kills. Note the importance of the WC stone.


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

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

[Diagram]

White kills

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


Second L+1-group, hane one side

[Diagram]

Second L+1-group, hane one side

The hane at BC may give some help in living.

[Diagram]

White cannot kill this way

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

[Diagram]

White kills

To kill, W1 can go straight to the 2-2 point. After W7, Black is dead. See the addendum of the rectangular six in the corner page. As before, the WC stone is important.


Second L+1-group, hane both sides

[Diagram]

Problem

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

[Diagram]

Problem

The attachment at W1 leads to ko.


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.


See also:


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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.
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