100 Challenging Go Problems For 100 Days Of Study / Problem 1

Problem 1 (White to play)  

According to the book, this problem was solved by 12% of the respondents.

My choice: As a 2d (KGS) my eyes turn to the top side and the right side. In the top right, White can choose to reinforce at A or pincer at B. Given the white group in the lower right is not settled and can be attacked, reinforcing at C looks a proper move which also puts some pressure on the top right. D is probably too slow. So my choice goes to C but I could fathom any move between B and C.

The book's "correct answer"  

The book's answer: (my rewording)

Turning at forces the sequence up to . This provides a wall to extend from at which then also takes the ideal spot to pincer . KataGo "sees" this sequence too but favors another move

Why is forced?  

If takes the ideal point for himself, then White forces Black into a low position. This is KataGo's sequence. The book gives a different sequence but with a similar result.

KataGo's answer  

KataGo's answer: with 100K playouts and counting KataGo prefers to make a base for the lower right.

and C both get a W+3.3 valuation, compared to 2.6 for the book's solution. After two incidental forcing moves at and , Black pincers the white corner at .

This is almost what the book gives as a failure diagram. It says that after Black will play and this is too easygoing by White.

My appreciation: upon seeing the solution in the book, I could appreciate the straightforward and active sequence. The final move being a dual purpose move indeed appealed to me as an ideal move. Although KataGo confirms my initial choice, I agree with the book that it gives the initiative to Black, who can pincer the upper right corner.