EVENT
BOARDSIZE 19
SETUP W D16 D14 D10 D4 H3 H5 K5 R4 R3 S3 T4 S5 S6 Q6 R6 T6 O7 S7 Q17 P18 
SETUP B K3 Q3 Q4 Q5 R5 P6 P7 P8 Q7 R7 R8 S8 Q16 P17 F17 K16 Q14 M4 
MARK A@P18
COM
Problem 98. Black to play.  

What should Black do when White hanes at A ? 
ENDCOM
B 1 P16
USER
CORRECT ANSWER
ENDUSER
COM
Correct Answer.

Connecting at Black 1 is the joseki move.
ENDCOM
  VAR
  B 1 Q18
  COM
  Failure.

  The atari of Black 1 is also a joseki move, but, ...
  ENDCOM
  W 2 R17
  B 3 R18
  W 4 P16
  B 5 O17
  W 6 O18
  B 7 S18
  W 8 R16
  B 9 Q15
  W 10 N17
  B 11 O16
  W 12 N15
  B 13 O15
  W 14 O14
  B 15 N16
  W 16 M16
  B 17 P15
  W 18 M15
  MARK A@M18
  COM
  ... after the sequence to White 18, Black's moyo has been drastically
  reduced. Instead of 18, White could also play A.
  ENDCOM
    VAR
    W 18 M18
    MARK @@M15
    COM
    If White chooses to defend at 18, instead of @, ...
    ENDCOM
    B 19 M15
    COM
    ... Black can increase the size of his moyo by cutting at 19.
    ENDCOM
    W 20 L15
    COM
    White will then atari at 20 ...
    ENDCOM
    B 21 M14
    W 22 L16
    MARK A@K17
    COM
    ... and connect at 22, aiming next to play A. Black gets a moyo,
    but at the expense of weakening his two stones at the top.
    <=
    ENDCOM
    ENDVAR
  B 19 M17
  COM
  The atari of Black 9 is small.
  ENDCOM
  W 20 L17
  B 21 N18
    VAR
    B 21 M18
    COM
    Black might be able to get more profit by descending to 21, ...
    ENDCOM
    W 22 L16
    B 23 N18
    COM
    ... then capture with 23, ...
    ENDCOM
    W 24 K15
    COM
    ... but the two black stones at the top left are even weaker
    than in the preceding diagram after White 24.
    <=:
    ENDCOM
    ENDVAR
  W 22 M18
  B 23 N17
  W 24 L16
  COM
  Moreover, Black's stones at the top left are weakened after White
  connects at 6.
  <=
  ENDCOM
  ENDVAR
W 2 R17
  VAR
  W 2 Q18
  COM
  Variation.

  Connecting at 2 is also a joseki move.
  ENDCOM
  B 3 O18
  W 4 R16
  B 5 R15
  W 6 S16
  B 7 N17
  MARK A@S18
  COM
After 7, Black's moyo is almost as large as in the Correct Answer.
  White has an opening into Black's moyo in the upper right, but
this is compensated for by the bad aji White has if Black plays
  at A. (See Get Strong at Life and Death, Problem 101.)
  <=
  ENDCOM
  ENDVAR
B 3 O18
W 4 S15
B 5 S14
W 6 R15
B 7 R14
W 8 Q18
COM
White lives in the corner with the sequence to 8, but ...
ENDCOM
B 9 N17
COM
... Black gets a massive moyo when he connects at 9.
<=
ENDCOM