Long L group

The long L group  

The black shape in this corner is the long L group. It controls more corner space than the L group, and this greatly improves its chances for survival.

This shape is also sometimes referred to as The L group with 1 arm.

a strange ko  

This is White's best attack. She produces a somewhat strange ko in the corner. This is known as a ten thousand year ko.

Black should not play at a because it results in a direct ko. The ten thousand year ko is much better for Black. Refer to that page for more detail.

The long L group with hane one side  

When the hane stone is on this side, nothing changes. The sequence above still applies.

The long L group with hane one side  

When the hane stone is on the other side, things get a bit more interesting.

Ten-thousand year ko  

White can still get a ten-thousand year ko, but the sequence is now different.

Black lives  

The usual clamp at does not work. Thanks to the stone, lives, and White cannot bridge under at a.

Long L group with an extra liberty  

This diagram is a modified one with extra liberty at a for the black group. Note that Black is unconditionally alive.

Black can answer at 4  

The attack by and fails. Black has an excellent way to live - is the key move to remember, aiming to play at a...

Variation 1: seki  

If White answers at , Black will play at . The result is a gote seki for Black - the same as living unconditionally when considered in terms of life and death.

Variation 2: still alive  

( at 6)

The strongest attempt for White (if White must kill) is to play atari at in this diagram. But Black sacrifies yet another stone at , and takes back with . . .

Variation 2a: oiotoshi  

If White plays at , will cause White to be caught in a connect-and-die (a kind of shortage of liberties).

Variation 2b: big capture  

here won't start a ko either. After , White at a, Black at b, it will be obvious that Black is unconditionally alive. The extra liberty comes in very handy here.

Descent outside (1)  

White has descended to the edge with . If Black doesn't answer, he dies unconditionally.

Descent outside (1)  

Black's attempt at a ko lacks liberties instead.

Note that can also be played at .

Hane outside  

Gokyo Shumyo, Section 1, Problem 18 / Solution includes this variation. creates a defect: now is atari, making the previous diagram fail.

Hane outside  

( at )

Subsequently, if White plays at , Black lives with and .

Descent outside (2)  

White descends the other way. It is still the case that White to play can kill Black unconditionally.

Descent outside (2)  

This is also shortage of liberties. Black can't play at a after .