EVENT
BOARDSIZE 19
SETUP W C17 D14 D3 D2 E2 F2 F3 G4 H3 D7 C8 E7 C6 C5 C4 Q18 O17 L17 
SETUP B G3 E3 E4 F4 D4 D5 D6 C7 B7 B4 B3 C3 O3 Q4 R5 Q16 R17 R14 
MARK 1@D14
COM
Problem 153. Black to play.  

White makes a large moyo with 1. Black has taken a lot of territory
in the three corners, so all he needs to do is to break up this
moyo. Should Black play a light erasing move or attack at the
base of White's moyo ? 
ENDCOM
B 1 K16
USER
CORRECT ANSWER
ENDUSER
COM
Correct Answer.

Erase with a shoulder hit.
Black is sated with solid territory, so he doesn't need to fight
for more. It is sufficient just to erase White's moyo with the
shoulder hit of 1. Remember the proverb: 'When you want to erase,
hit at the shoulder !'
ENDCOM
  VAR
  B 1 D17
  COM
  The attachment doesn't work.

  Attaching at 1 might also be considered.
  ENDCOM
  W 2 D16
  B 3 E16
  COM
  Black hopes to make sabaki with 3, but ...
  ENDCOM
    VAR
    B 3 E17
    COM
    Black's stones are heavy.

    Drawing back with 3 is also bad.
    ENDCOM
    W 4 C18
    B 5 E16
    W 6 D15
    B 7 J17
    COM
    After 7, ...
    ENDCOM
    W 8 G17
    COM
    ... White invades at 8, and ...
    ENDCOM
    B 9 G16
    W 10 H17
    B 11 H16
    W 12 J18
    B 13 J16
    W 14 K17
    COM
    ... the black stones are again heavy after the moves to 14. There
    is a proverb that says, 'when you want to make sabaki, attach
    !' In this case, the proverb does not apply.
    <=
    ENDCOM
    ENDVAR
  W 4 E17
  B 5 D18
  W 6 E18
  B 7 D15
  W 8 C16
  B 9 F16
  W 10 C15
  B 11 F18
  W 12 C18
  B 13 F17
  W 14 D19
  MARK \t@L17
  COM
  ... up to 14, Black's stones have no eyes and are blocked from
  extending by the marked stone. These4 stones have become a burden
  on Black.
  <=
  ENDCOM
  ENDVAR
  VAR
  B 1 J17
  COM
  An ideal result for White.

  If Black invades at 1, ...
  ENDCOM
  W 2 G17
  COM
  ... White will attach with 2.
  ENDCOM
  B 3 J15
  COM
  All Black can do is to run away into the center with 3, ...
  ENDCOM
  W 4 L15
  COM
  ... but White continues the chase with 4. By attacking theses
black stones, White will be able to make territory. This is an
  ideal result for White.
  <=
  ENDCOM
  ENDVAR
  VAR
  B 1 Q10
  MARK \t@R14 \t@R5
  COM
  Good shape, but ...

  Black 1 is a slow and deliberate way of playing and makes an
  ideal shape with Black's two marked stones.
  ENDCOM
  W 2 H16
  MARK A@K16
  COM
  On the other hand, White 2 is also a good point, The result here
  must be considered even. Clearly, it is better to disrupt White's
  moyo by playing the moves beginning with the shoulder hit at
  A.
  <=
  ENDCOM
  ENDVAR
W 2 K17
  VAR
  W 2 L16
  COM
  A successful erasure.

  White could also push up with 2 ...
  ENDCOM
  B 3 K15
  W 4 L15
  COM
  ... and 4, ...
  ENDCOM
  B 5 K14
  W 6 J18
  COM
  ... then slide to 6.
  ENDCOM
  B 7 L14
  COM
  But 7 is a thick move, giving Black influence throughout the
  board. Black has successfully erased White's moyo and his three
  corners are still intact.
  <=
  ENDCOM
  ENDVAR
B 3 J16
W 4 L16
B 5 K14
W 6 L15
B 7 H13
MARK A@M13
COM
The moves to 7 are joseki. After this, White will aim to play
at A to set up a base from which to attack the right side and
the top right corner.
<=
ENDCOM