4-4 point one-space low pincer invasion, block
After White's approach and Black's pincer , Black blocks the invasion of at if he has a stone near . The idea is to form a wall plus an extension at an ideal distance, a typical construction of a moyo, while White gets corner territory and sente.
and are natural, but then and used to complete the basic variation before AI brought new insights into the game. The idea is here for to protect against a placement at A while makes a loose connection with two keimas.
If the marked stone is not present, this variation has been evaluated as bad for Black. When White plays around herself, theinfluence of the black wall is reduced.
AI has improved upon the former, first by dropping to instead of in the previous diagram. This move aims to either destroy Black's left side territory, or require Black to spend another move. Next emphasizes the strength of the wall. and aim to break out of the corner into the right side, or again force Black to spend another move. Having obtained strength with his wall plus extension, Black then usually leaves the area. The focus is not so much on moyo building anymore.
Extending to was already known prior to AI but White would still drop back at . If focuses on the left side territory, White could cut like this later. The moves to White 11 (at a) are one possible continuation.
The old joseki in this cae was for Black to defend the cut directly with . The disadvantage of this move is that it leaves the large move of as aji. If Black blocks with at , White has a lot of aji here which might be used to invade Black's left-side moyo. But if Black draws back to instead, White can make a rather large reduction of his territory in sente. Instead of , white could also play at .
is another joseki move. The sequence to is forced, after that Black can choose to build thickness with a or fight immediately with b. a has been most common.
The Suzuki-Kitani Small Joseki Dictionary says that this joseki is good for Black.
After , this sequence is to be expected. White has sente, but Black's influence is large. However, note that there is a White invasion at A that is hard to deal with. For example:
In this line Black dies and the game is over. Instead the best Black can hope for (if they play on the outside) is ko:
If Black plays , he should not forget the important exchange of for . After , White is floating in the center, while Black is both strong and in a position to make territory on both sides. If White does not answer in the corner, Black can get a ko.
Black should not be afraid of this . Black can maintain his connection to the outside world, while White still has to come back in the corner.
White can also answer here. The Black stones on the left make inefficient shape. The circled stone on the star point ends up looking inefficent. White retains significant endgame aji at a. Black's stones on top are low. Although White's center is floating and can later be attacked, the stones are light, flexible, and efficient.