EVENT
BOARDSIZE 19
SETUP W D17 C15 C6 C4 D3 E3 
SETUP B E4 F3 F4 K4 Q4 Q16 
COM
Problem 171. Black to play.  

White has made a corner enclosure in the upper left corner. Where
should Black now play ? 
ENDCOM
B 1 Q10
MARK \t@K4
USER
CORRECT ANSWER
ENDUSER
COM
Correct Answer.

Black should make a sanren-sei on the right side with 1. With
the marked stone at the bottom, this moyo is like an eagle, spreading
its great wings in flight.
<=
ENDCOM
  VAR
  B 1 R10
  COM
  Failure.

  Black 1 here is too low, as it would be open to a capping move.
  <=
  ENDCOM
  ENDVAR
  VAR
  B 1 K17
  COM
  Passive.

  Black plays 1 in order to neutralise the influence of White's
  corner enclosure in the upper left corner, but this move is dubious.
  ENDCOM
  W 2 R10
  COM
  White will play 2 ...
  ENDCOM
  B 3 R7
  W 4 R13
  COM
  ... and 4 to stake out a position on the right side. Of course,
  we can't say that Black's position is bad, but it is going to
  be a long, hard game for him.
  <=
  ENDCOM
  ENDVAR
W 2 O17
COM
Next, White will approach with 2, ...
ENDCOM
B 3 Q14
W 4 Q18
B 5 R17
W 6 L17
COM
... the continuation to White 1 is one possibility.
ENDCOM
B 7 Q6
COM
At this point, Black will strengthen his position in the lower
right with 7.
<=
ENDCOM