EVENT
BOARDSIZE 19
SETUP W C17 D16 F16 L17 O17 Q18 K4 D4 F4 P9 
SETUP B R17 Q16 Q14 R9 Q3 M4 C6 C11 C14 B16 Q11 
MARK 2@Q11 1@P9
COM
Reference Diagram to Problem 165. White to play.  

Black 2 in answer to the white capping move of 1 is possible,
too. What should White do now ?
ENDCOM
W 1 R3
MARK \t@Q11
USER
CORERECT ANSWER
ENDUSER
COM
Correct Answer.

Responding the white cap with the marked black stone is also
possible, but now White 1 ...
ENDCOM
B 2 R4
W 3 Q4
COM
... and 3 become powerful moves.
ENDCOM
B 4 P3
COM
If Black plays 6, Black has fallen into White's trap.
ENDCOM
W 5 R8
B 6 Q8
W 7 Q9
B 8 R10
COM
The sequence continues up to Black 8, and then ...
ENDCOM
W 9 R7
B 10 P8
W 11 R5
B 12 S4
W 13 P4
B 14 R2
W 15 S5
B 16 S3
W 17 O8
MARK \t@R4 \t@Q8
COM
... the moves to White 17 follow. White has driven a wedge of
territory between the two marked black stones. This is a big
turnaround from before White invaded; it was Black who then dominated
this side of the board.
<=
ENDCOM