Long L group
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The standard 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.
The long L group without outside liberties
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 without outside liberties, with hane on one side
When the hane stone is on this side, nothing changes. The sequence above still applies.
When the hane stone is on the other side, things get a bit more interesting.
The usual clamp at does not work. Thanks to the
stone,
lives, and White cannot bridge under at a.
The long L group with an outside liberty
This diagram is a modified one with extra liberty at a for the black group. Note that Black is unconditionally alive.
The attack by and
fails. Black has an excellent way to live - by playing at
, aiming to play at a...
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.
( 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
. . .
If White plays at ,
will cause White to be caught in a connect-and-die (a kind of shortage of liberties).
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.
The long L group with a descent outside (1)
Gokyo Shumyo, Section 1, Problem 18 / Solution includes this variation. creates a defect: now
is atari, making the previous diagram fail.
The long L group with a descent outside (2)
White descends the other way. It is still the case that White to play can kill Black unconditionally.