EVENT
BOARDSIZE 19
SETUP W C17 C16 D15 C13 C11 Q4 R16 
SETUP B C18 D17 E18 F16 E14 D4 P16 
COM
Problem 165. Black to play.  

Taking into account Black's influence in the upper left, what
is Black's strongest move ? 
ENDCOM
B 1 Q14
USER
CORRECT ANSWER
ENDUSER
COM
Correct Answer.

Black should play 1, making outside influence and restricting
White to the corner.
ENDCOM
  VAR
  B 1 K4
  COM
  Failure.

  Extending to Black 1 at the bottom is not good.
  ENDCOM
  W 2 Q14
  MARK \t@C13 \t@E14
  COM
  White will play 2 and stake out a claim on the right side. White
  2 also inhibits the development of a black moyo at the top, so
  now the exchange of the marked black and white stones in not
  good for Black.
  <=
  ENDCOM
  ENDVAR
  VAR
  B 1 R17
  COM
  Failure.

  ENDCOM
  W 2 S17
  B 3 Q17
  W 4 S15
  COM
  The sequence to White 4 is a joseki, ...
  ENDCOM
  B 5 M16
  MARK \t@C13 \t@E14
  COM
  ... but the extension of Black 5 is unsatisfactory because it
  doesn't make an efficient moyo with respect to the marked black
  stone on the left.
  ENDCOM
    VAR
    B 5 P14
    COM
    Black 5 here certainly makes a moyo on a grand scale, but Black's
    position at the top is too thin to support it, so White will
    have an easy time invading it.
    <=
    ENDCOM
    ENDVAR
  W 6 K4
  COM
  <=
  ENDCOM
  ENDVAR
W 2 P17
  VAR
  W 2 R14
  COM
  Variation.

  White could also attach on the right with 1.
  ENDCOM
  B 3 R13
  W 4 Q13
  B 5 R15
  W 6 S14
  B 7 P14
  W 8 S15
    VAR
    W 8 R12
    COM
    If White 7 here, ...
    ENDCOM
    B 9 S15
    COM
    ... Black takes profit in the corner ...
    ENDCOM
    W 10 S13
    B 11 Q16
    COM
    ... with the sequence to 11.
    <=
    ENDCOM
    ENDVAR
  B 9 Q12
  COM
  The sequence to Black 9 is a joseki. Since the ladder favours
  Black, he is happy with this result.
  <=
  ENDCOM
  ENDVAR
B 3 O17
W 4 Q17
MARK 2@P17
COM
Against White 2 and 4, ...
ENDCOM
B 5 O16
MARK 3@O17
COM
... Black maps out a moyo at the top with 3 and 5.
<=
ENDCOM