4-4 point low approach low extension, standard joseki
This is the standard joseki mentioned in 4-4 point low approach low extension.
This page aims to give a deeper discussion to this joseki.
Assuming there is some white stone or structure, say at . We will say that
and
are miai. In fact,
is very big and gives the black corner a base.
(The main alternative to is Black a in the centre. The use of this play is discussed at 4-4 point low approach low extension, standard joseki, pushing in the centre. See also [1] below.)
Losing the base in the corner
For black to tenuki when is played is not a good idea.
gains substantially in territory and sets up an attack.
or a is the correct play, but black has not gained much territory or influence in this move. For
to play at b is a dangerous choice.
After ,
,
, black's territory is all gone and black becomes eyeless. There is an important caveat here: we assume that the ladder is good for white. However, white can always choose to play a ladder breaker somewhere in the lower right, so the danger still lurks.
If the ladder is good for black, then and
is the tesuji to counter
. Further, if white a, then black b, and the two white stones gets captured.
This line of resistance is still not enough. After , if white a, then black b, then is reverts to the previous diagram, where white is captured.
The ladder which was mentioned earlier is this. followed by
is a strong move. The crucial question is whether the ladder at a works after
.
Finally, a hamete (joseki trick) by black if the ladder is not good for black. is a the joseki trick and
is the correct move, and black gains nothing.
must not be played at
, otherwise black will play
, capturing three white stones, and there is no ladder to talk about.
[1] Addendum
Later, it is possible to answer with
, securing the base. However, the exchange of
and
strengthens white, losing the possibility of any invasion in white's two space expansion on the top. Also, white gains significantly in the exchange of
and
(because if black plays at
, black can aim at a to capture a white stone). So the price to pay for the tenuki is considerable.
The good thing is, the invasion at is no longer possible. Black applies the
,
tesuji mentioned above but this time it works without the precondition of a working ladder. The reason is, with
, black can play at
, and white is finished.