EVENT
BOARDSIZE 19
SETUP W D16 F16 L17 O17 Q18 Q12 R7 R4 P3 
SETUP B R17 Q16 Q14 R9 P9 D4 D10 C14 
MARK \t@Q12
COM
Problem 49. Black to play.  

The marked white stone has a lot of room to maneuver. How should
Black attack ? 
ENDCOM
B 1 P11
USER
CORRECT ANSWER
ENDUSER
COM
Correct Answer.

The shoulder hit of Black 1 is severe.
ENDCOM
  VAR
  B 1 O12
  COM
  Failure.

  Capping with Black 1 doesn't work ...
  ENDCOM
  W 2 Q10
  COM
  ... because White will peep with 2.
  ENDCOM
  B 3 Q9
  W 4 O11
  B 5 P11
  W 6 P12
  B 7 N11
  W 8 O13
  B 9 O10
  W 10 P14
  COM
  White now extricates her stones with the sequence to 10. White's
stones are safe, but the three black stones in the upper right
  corner are in trouble.
  <=
  ENDCOM
  ENDVAR
  VAR
  B 1 O13
  COM
  Failure.

  Attacking from above with Black 1 ...
  ENDCOM
  W 2 O12
  B 3 N12
  COM
  ... and 3 is out of the question.
  ENDCOM
  W 4 O11
  B 5 N13
  W 6 N11
  B 7 M11
  W 8 M10
  B 9 L11
  W 10 N9
  MARK \t@R9 \t@P9
  COM
  After White 10, the two marked stones are isolated and without
  a base.
  <=
  ENDCOM
  ENDVAR
W 2 P12
COM
If White 2, ...
ENDCOM
B 3 O12
COM
... Black presses with 3 and ...
ENDCOM
W 4 P13
COM
... White has to turn at 4.
ENDCOM
B 5 O16
COM
Black now leans on White's stones above with 5.
ENDCOM
W 6 O13
MARK 5@O16
COM
White might want to ignore Black 5 and turn at 6.
ENDCOM
  VAR
  W 6 N16
  COM
  If White defends the top with 6, ...
  ENDCOM
  B 7 N15
  COM
  ... Black keeps up the pressure with 7.
  ENDCOM
  W 8 M16
  COM
  After White 8, ...
  ENDCOM
    VAR
    W 8 O15
    COM
    If White plays at 8 here, ...
    ENDCOM
    B 9 O14
    COM
    ... Black ataris at 9 here. The white stones on the right are
    trapped.
    ENDCOM
    ENDVAR
  B 9 O13
  COM
  ... Black turns at 9 and the white stones on the right are trapped.
  <=
  ENDCOM
  ENDVAR
B 7 N17
COM
Black would the play 7 ...
ENDCOM
W 8 N18
  VAR
  W 8 M13
  B 9 N16
  COM
  ... and 9, taking a large profit at the top. Black is satisfied
  with this result.
  <=
  ENDCOM
  ENDVAR
B 9 N16
W 10 O18
COM
If White defends upon to 10, ...
ENDCOM
B 11 N13
W 12 N12
B 13 O11
W 14 N14
B 15 M13
W 16 O14
B 17 M14
COM
... Black traps White's stones on the right with the sequence
to 17.
<=
ENDCOM