EVENT
BOARDSIZE 19
SETUP W P17 R16 
SETUP B K17 N17 R14 R11 
COM
Problem 105. Black to play.  

The small-knight enclosure secures the corner, but if Black has
built strong positions around it, an invasion is possible. Where
should Black invade ? 
ENDCOM
B 1 Q17
USER
CORRECT ANSWER
ENDUSER
COM
Correct Answer.

Black 1 is the point to gauge out White's base.
ENDCOM
  VAR
  B 1 PASS
  ENDVAR
W 2 Q16
B 3 R17
W 4 P16
  VAR
  W 4 Q18
  COM
  Failure.

  White might respond with 4 ...
  ENDCOM
  B 5 R18
  W 6 P18
  COM
  ... and 6 here.
  ENDCOM
  B 7 S16
  W 8 S15
  B 9 S17
  W 10 R15
  COM
  However, after she defends with 10, ...
  ENDCOM
  B 11 P16
  COM
  ... Black cuts with 11 and White's position collapses.
  <=
  ENDCOM
  ENDVAR
B 5 S16
W 6 S15
B 7 S17
W 8 R15
B 9 S14
W 10 T15
B 11 P18
W 12 O18
B 13 Q18
COM
Up to 13, Black lives in the corner.
ENDCOM
W 14 O17
B 15 N18
COM
After 15, however, White's group is eyeless and will become a
target of attack.
<=
ENDCOM