EVENT
BOARDSIZE 19
SETUP W D4 F4 P3 R4 R18 R17 Q16 Q15 P17 P14 
SETUP B D17 C15 D10 C6 Q13 Q14 R12 R15 R16 S17 L17 
COM
Problem 160. Black to play.  

There are a lot of point where you can invade, but any invasion
you make should take into account White's thickness on the right.
ENDCOM
W 1 H16
MARK A@H18
USER
CORRECT ANSWER
ENDUSER
COM
Correct Answer.

Playing on the fourth line with White 1 is the best move. With
a high move, escaping will be easy. For Black to try to link
up at A would be submissive, so it is out of the question.
ENDCOM
  VAR
  W 1 J17
  COM
  Failure.
   A deep invasion with White 1 is dubious.
  ENDCOM
  B 2 J15
    VAR
    B 2 G17
    MARK 1@J17
    COM
    Variation.

    Another way for Black to refute White 1 is to play 2 in response.
    This is a good move because it is in the right direction from
    the corner enclosure.
    <=
    ENDCOM
    ENDVAR
  W 3 K16
  B 4 O16
  MARK 2@J15
  COM
  After Black 2 and 4, which hit White at her vital points, you
  will probably agree that the momentum of the game is in Black's
  favour.
  ENDCOM
  W 5 O15
  MARK 4@O16
  COM
  For example, if White answers 4 with 5, ...
  ENDCOM
  B 6 O17
  W 7 P18
  B 8 N15
  COM
  ... the sequence will continue up to 8. Black clearly has the
  advantage.
  <=
  ENDCOM
  ENDVAR
  VAR
  W 1 E15
  COM
  Failure.

  White 1 here is also a bad move, ...
  ENDCOM
  B 2 F16
  COM
  ... because Black can answer with the knight move at 2, eliminating
  his thinness on the upper side.
  <=
  ENDCOM
  ENDVAR
B 2 L15
COM
Black's best course is to jump out with 2.
ENDCOM
  VAR
  B 2 H14
  COM
  Variation.

  Black might cap with 2 intending to build a moyo at the top.
  ENDCOM
  W 3 K16
  COM
  However, White replies with the shoulder hit at 3 and ...
  ENDCOM
  B 4 L16
  W 5 K15
  B 6 L15
  W 7 K14
  B 8 M13
  W 9 K12
  MARK 2@H14 8@M13 6@L15 4@L16
  COM
  ... escapes into the center with the moves to 9. Black's wall
  of 4, 6, and 8 is now neutralised by White's wall on the right
  and, with White's thickness in the center, Black 2 has failed
  to increase the size of his moyo on the left.
  <=
  ENDCOM
  ENDVAR
W 3 H14
COM
However, White also jumps into the center with 3 ...
ENDCOM
B 4 L13
W 5 H12
COM
... and 5, and Black's moyo is erased.
<=
ENDCOM