EVENT
BOARDSIZE 19
SETUP W D16 D10 D4 K4 N4 
SETUP B P4 Q3 Q9 Q16 K16 
COM
Problem 70. Black to play.  

All the big points have been taken, with both sides staking out
their own moyos. Where should Black play next ? 
ENDCOM
B 1 Q14
MARK \t@Q9
USER
CORRECT ANSWER
ENDUSER
COM
Correct Answer.

Now is the time for Black to solidify his moyo. He should play
1 in the direction of the marked stone so as to strengthen the
thinnest part of his position.
<=
ENDCOM
  VAR
  B 1 F17
  COM
  Failure.

  Expanding his moyo with 1 is certainly a good point, but ...
  ENDCOM
  W 2 R14
  COM
  ... White will approach at 2.
  ENDCOM
  B 3 R15
  W 4 Q14
  B 5 O16
  W 6 R11
  MARK B@C16 A@C17
  COM
  With the sequence to White 6, Black's moyo has been erased. Black
  can aim at the invasion at A, but White would block at B and
  build a moyo along the left side.
  <=
  ENDCOM
  ENDVAR