EVENT
BOARDSIZE 19
SETUP W C16 B16 D16 D17 E18 F18 F17 C8 D6 D4 E3 R10 P15 H13 H14 H15 J15 K15 L15 M16 K17 J18 O18 O17 P18 O16 
SETUP B E17 E16 F16 G15 G17 H17 B15 C14 D13 F13 D10 E8 Q4 Q18 P17 P16 Q16 R16 Q14 M15 N15 O15 N13 L14 K14 J14 
COM
Problem 116. Black to play.  

How should Black play in this position ? 
ENDCOM
B 1 R8
USER
CORRECT ANSWER
ENDUSER
COM
Correct Answer.  

Black should drive White in the direction of his thickness above
with 1.  
ENDCOM
W 2 P10
COM
If White jumps to 2, ...  
ENDCOM
B 3 P8
COM
... Black reinforces his position in the lower right with 3.
ENDCOM
W 4 R13
COM
After White extends to 4, ...  
ENDCOM
B 5 Q11
  VAR
  B 5 R11
  MARK @@Q11
  COM
  If Black doesn't like the results of the variations after Black
  @, he can simply attach with 5 and ...
  ENDCOM
  W 6 S11
    VAR
    W 6 Q11
    COM
    If White presses with 6, ...
    ENDCOM
    B 7 R12
    W 8 Q12
    B 9 S13
    MARK 7@R12
    COM
    ... Black will play 7 and 9. Black's stones are secure, but White's
    are still without a base.
    <=
    ENDCOM
    ENDVAR
  B 7 Q11
  W 8 Q10
  B 9 S12
  W 10 S10
  B 11 R12
  COM
  take the territory in the upper right with the sequence to 11.
  <=
  ENDCOM
  ENDVAR
  VAR
  B 5 N9
  MARK A@R11 @@Q11
  COM
  Failure.

  Black 5 is not all that bad, but it is not as decisive as the
  two correct answers @ and A.
  ENDCOM
  W 6 S8
  B 7 S7
  W 8 S9
  B 9 R7
  W 10 R14
  MARK \t@P15
  COM
  White lives with the sequence to 10, while Black has secured
  the territory in the lower right. The aji of the marked stone
  will be a bit annoying for Black.
  <=
  ENDCOM
  ENDVAR
W 6 Q10
  VAR
  W 6 P11
  MARK 5@Q11
  COM
  When Black plays 5, White might block with 6.  
  ENDCOM
  B 7 Q12
  COM
  Black falls back with 7 and ...  
  ENDCOM
  W 8 Q10
  COM
  ... White must connect at 8.  
  ENDCOM
  B 9 S11
  COM
  Black next jumps to 9 and secures the territory in the upper
  right.  
  ENDCOM
  W 10 R11
  B 11 R12
  W 12 S10
  B 13 S12
  W 14 M10
  MARK B@N10 A@S8
  COM
  If White attaches at A, she can make only one eye, so she must
  run away with 9. White 9 is thin and there is a chance that Black
  might attach at B, but the ensuing fight could spill over Black's
  position below.  
  ENDCOM
  B 15 M8
  W 16 K10
  B 17 L11
  W 18 L10
  B 19 K8
  COM
  Therefore it is better for Black to chase the white stones toward
  his strong position on the left with 19. Black's result is too
  good, so White cannot play this way.  <= 
  ENDCOM
  ENDVAR
  VAR
  W 6 S8
  MARK @@Q10
  COM
  Instead of @ in the Correct Answer, White could attach with 6
  here. Black might be tempted to answer at @, but this is a bit
  loose.  
  ENDCOM
  B 7 S7
  COM
  Simply responding with 7 ...  
  ENDCOM
  W 8 R9
  B 9 Q8
  COM
  ... and 9 gives Black a strong position in the lower right. <=
  ENDCOM
  ENDVAR
  VAR
  W 6 R11
  COM
  White can also defend the side with 6.  
  ENDCOM
  B 7 Q10
  COM
  Black would then push trough with 7 ...  
  ENDCOM
  W 8 R9
  B 9 Q9
  COM
  ... and 9.  
  ENDCOM
  W 10 S8
  B 11 R7
  W 12 S7
  B 13 R6
  COM
  White lives on the right, but Black gets a thick wall in the
  center. This is a satisfactory result for Black.  <= 
  ENDCOM
  ENDVAR
B 7 S12
MARK 5@Q11
COM
... Black takes profit with 5 ...and 7.  
ENDCOM
W 8 S9
MARK 7@S12
COM
After Black 7, White might play 8, threatening Black's territory
below and to cut off the black stone on the second line.  
ENDCOM
  VAR
  W 8 R11
  MARK 7@S12
  COM
  White 8 is not a good answer to Black 7.  
  ENDCOM
  B 9 R12
  W 10 Q12
  B 11 S13
  MARK 9@R12 \t@Q11
  COM
  Black plays 9 and 11. White is left with the bad aji of the marked
  stone and her stones still lack eye shape. This result is unsatisfactory
  for her.  <= 
  ENDCOM
  ENDVAR
B 9 S8
COM
Black blocks at 9, and ...  
ENDCOM
W 10 R12
B 11 S11
W 12 R11
MARK 10@R12
COM
... White cuts through with 10 and 12.  
ENDCOM
B 13 S10
W 14 R9
B 15 T9
COM
But Black links up with 15. White's stones still don't have eyes.
<= 
ENDCOM