EVENT
BOARDSIZE 19
SETUP W M16 R14 Q10 R6 B16 C14 C11 
SETUP B C17 D16 F16 K16 O16 Q16 Q4 O4 K4 D4 
MARK 1@M16
COM
Problem 55. Black to play.  

The invasion of White 1 often occurs in handicap games. How should
Black respond ? 
ENDCOM
B 1 L15
USER
CORRECT ANSWER
ENDUSER
COM
Correct Answer.  

The diagonal move of Black 1 is the strongest response.
ENDCOM
  VAR
  B 1 N15
  MARK A@L15
  USER
  CORRECT ANSWER
  ENDUSER
  COM
  Correct Answer.

  Playing the diagonal move of Black 2 from the right is also correct.
  It often transposes into the position of the Correct Answer starting
  with Black A.
  <=
  ENDCOM
  ENDVAR
  VAR
  B 1 K14
  USER
  CORRECT ANSWER
  ENDUSER
  COM
  Correct Answer.

  Jumping to 2 is also possible.
  ENDCOM
  W 2 M14
  COM
  After White 2, ...
  ENDCOM
  B 3 P13
  COM
  ... Black jumps to 3, attacking the white stones on both the
  right and left. If you are good at fighting, you can play this
  way.
  <=
  ENDCOM
  ENDVAR
  VAR
  B 1 K17
  COM
  Failure.

  Black 1 is overly defensive.
  ENDCOM
  W 2 M14
  COM
  After White jumps to 2, ...
  ENDCOM
    VAR
    W 2 M18
    MARK 1@K17
    COM
    Variation.

    White might respond to Black 1 by jumping to 2.
    ENDCOM
    B 3 N15
    COM
    In this case, Black will certainly play at 3.
    <=
    ENDCOM
    ENDVAR
  B 3 M17
  COM
  ... Black must defend again at 3. Black has enormous power at
  the top, so he must not play so submissively.
  <=
  ENDCOM
  ENDVAR
  VAR
  B 1 M15
  COM
  Failure.

  Attaching at 1 is not recommended.
  ENDCOM
  W 2 L15
  B 3 L16
  W 4 N15
  B 5 M17
  W 6 M14
  B 7 N17
  COM
  Black can take territory at the top, but White's ponnuki gives
  her the strategic advantage.
  <=
  ENDCOM
  ENDVAR
  VAR
  B 1 M17
  COM
  Failure.

  Attaching underneath with Black 1 is also bad.
  ENDCOM
  W 2 L17
  B 3 L16
    VAR
    B 3 N17
    MARK 1@M17
    COM
    Very bad.

    Drawing back with 3 after attaching at 1 is very bad.
    ENDCOM
    W 4 L16
    MARK \t@K16 A@R17
    COM
    White connects at 4 and the marked stone has lost much of its
    value. White also has the option of invading at A.
    <=
    ENDCOM
    ENDVAR
  W 4 N17
  B 5 M15
  W 6 M18
  B 7 N16
  W 8 K17
  COM
  White lives at the top with the moves to 8. Black has no territory
  and his thickness is not very effective.
  <=
  ENDCOM
  ENDVAR
W 2 M15
COM
Black confines White to the side with the moves from 2 ...
ENDCOM
B 3 M14
W 4 N14
B 5 N15
COM
... to 5. This is joseki.
ENDCOM
  VAR
  B 5 M13
  MARK B@N15 4@N14
  COM
  Failure.

  When White hanes with 4, Black must cut with B (5 in the Correct
  Answer). Playing 5 as here is timid.
  ENDCOM
  W 6 O15
  COM
  White gets a good result when she connects with 6.
  <=
  ENDCOM
  ENDVAR
W 6 M18
MARK B@P17 A@J17
COM
Continuation 1.

White jumps down to 6: she aims at either A or B.
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B 7 K18
COM
Black 8 is best, taking the larger territory on the left.
ENDCOM
  VAR
  B 7 O18
  COM
  Variation.

  Attacking from the right with Black 7 is also possible.
  ENDCOM
  W 8 J17
  COM
  White jumps to 8 and ...
  ENDCOM
  B 9 K17
  W 10 K18
  B 11 L17
  W 12 L18
  B 13 M17
  MARK 7@O18 A@K18 11@L17
  COM
  ... Black captures two stones with 11 and 13. Black's result
  is inferior to that beginning with Black A instead of 7.
  <=
  ENDCOM
  ENDVAR
W 8 P17
COM
With 8, White starts making two eyes at the top.
ENDCOM
B 9 P16
W 10 N16
B 11 O15
W 12 O17
B 13 Q17
W 14 Q18
B 15 R18
W 16 P19
COM
The moves to 16 are joseki and White's group at the top is alive.
Black is satisfied with his territory at the top left and his
thickness in the center.
<=
ENDCOM