Making Good Shape

Problem 1  

A Black stone is in atari. How should Black play (to make good shape) ?

Problem 123  

How can Black make shape for his stones?

Validity

Adum: As this book was written by two amateur players, I thought it would be interesting to show it to a professional. I showed four problems to JiangMingjiu. Two were deemed correct. One (problem 158) he said there were several possibilities, and the given move was possible but probably not optimal. The final problem (problem 4) is simply wrong. The correct answer is kosumi from the 3-rd line stone.

In summary, read this book with a grain of salt. There are some good ideas, but most problems have multiple solutions, and some are just wrong.

Problem 4  

Black to play.

How can Black keep White's stones heavy?

Book Answer Diagram 1  

Black should jump to 1 in Dia. 1, threatening to capture the two white stones at the top. If White defends with 2, Black extends to 3, increasing his thickness and keeping the white stones heavy and under attack.

Leela Zero replies to Black 1  

Black can cut the marked stone off. Leela Zero does not care.

Book Answer Diagram 2  

If White defends with the diagonal move of 2 in Dia. 2, Black draws back to 3, threatening to play at A and linking up his stones.

Real book answer?  

This also has a kosumi from a third line stone. :)

is one suggestion by Leela Zero.

Leela Zero suggestion  

This is Leela Zero's other suggestion.

Mingjiu's threat?  

Is one reason for Mingjiu's move the threat of ?

counter-attack  

If white plays the way you suggested after Mingjui's kosumi, black might counterattack with the tesuji-combination of 1 and 3, making a and b miai. If Black dislikes the bad aji after white connects at b and black cuts at a, he can also cut at b before 3 and then, when white plays at the point below b, play 3. In that case, white get's better shape in the center and black has less aji as long as two stones are in atari. In any case, even if the resulting position, with black getting profit in gote and white getting good shape in the center, is uninteresting for black, he will leave this posibility for later on, and therefor white has bad aji if he plays the one-point-jump.

slightly better shape for white?  

Because of this, white might prefer to play kosumi at 2 in order to strengthen his connection, and this seems to be the best sequence for both. In order to analyse this in more detail, take a look at the following diagram.

white escapes neatly  

If black plays the move that is suggested in the book, white 2 is a solid answer. if you compare this diagram to the previous one, it's obvious that the black stone at 1 would be better positioned at "a". If after this, black presses at b, white can escape to the right side. The point is that the exchange of 1 for 2, although it makes white a bit heavy, doesn't give black as much territory as Mingjui's kosumi did.

cut?  

The cut of black 1 leaves very much bad aji. White can play a or b and aim at the corner, and even if white does nothing at all, c on the top is white's sente. D is also a good point if white wants influence on the right side.

follow-up  

This shows another possibility. White forces his way out up to 9, then connects above 6, and black needs to defend the corner. After this...

follow-up  

White can cut at 4 to make Sabaki. In any case, this is too much bad aji, so black's cut seems to be irregular.

slightly vulgar, but depends on the overall position  

White can also consider 2 after 1, but he must be prepared for the violent cut of black 3, and needless to say, this depends on the overall position.

In conclusion Mingjui's kosumi seems more stable to me as it takes profit while attacking. White's shape is already thin and in cases like this it's usually better to aim at the opponent's thinness from a distance.

Diagonal jump question

page 51, Diagram 5  

jeffguy: Black has just played the marked stone and white responded with the marked stone. On page 50, the author explains that this white marked stone is the exact response he'd hoped for. "Black continues the attack with 1 in Diagram 5. If White persists in escaping with 2 to 8, Black secures the lower left with 9. In the process he has built influence facing the center. The important thing to notice here is that White has been unable to make eye shape. By escaping, he has only helped Black. It seems as if White might be able to counterattack at 'a', but this would only help Black build a thicker position in the center."

But White's play seems odd. I'd have expected:

page 51, Diagram 5, jeffguy alternative  

jeffguy: At this point, if Black cuts at 'a', white defends, and if Black captures , Black captures two stones, will surely live, and may escape to the center via . But what alternative does black have to 'a'? Try to live small with his three stones? I don't understand why in the book White pulled back with b instead of hane at .

fractic: After the exchange of a for b Black does not need to capture directly. Instead Black can connect at c. In this variation is a waste, therefore connecting at b right away is better.