(;
GM[1]
SZ[19]
AW[cc][cd][de][cg][ci][pp][qd]
AB[cb][dc][eb][fd][ef][dp][od]
C[Problem 165. Black to play.  

Taking into account Black's influence in the upper left, what is Black's strongest move ? ]
(;B[pf]
TE[2]
C[Correct Answer.  

Black should play 1, making outside influence and restricting White to the corner. ]
(;W[oc];B[nc];W[pc]
LB[oc:2]
C[Against White 2 and 4, ... ]
;B[nd]
LB[nc:3]
C[... Black maps out a moyo at the top with 3 and 5. <= ]
)
(;W[qf]
C[Variation.  

White could also attach on the right with 1. ]
;B[qg];W[pg];B[qe];W[rf];B[of]
(;W[re];B[ph]
C[The sequence to Black 9 is a joseki. Since the ladder favours Black, he is happy with this result. <= ]
)
(;W[qh]
C[If White 7 here, ... ]
;B[re]
C[... Black takes profit in the corner ... ]
;W[rg];B[pd]
C[... with the sequence to 11. <= ]
)))
(;B[jp]
C[Failure.  

Extending to Black 1 at the bottom is not good. ]
;W[pf]
TR[cg][ef]
C[White will play 2 and stake out a claim on the right side. White 2 also inhibits the development of a black moyo at the top, so now the exchange of the marked black and white stones in not good for Black. <= ]
)
(;B[qc]
C[Failure.  

]
;W[rc];B[pc];W[re]
C[The sequence to White 4 is a joseki, ... ]
(;B[ld]
TR[cg][ef]
C[... but the extension of Black 5 is unsatisfactory because it doesn't make an efficient moyo with respect to the marked black stone on the left. ]
;W[jp]
C[<= ]
)
(;B[of]
C[Black 5 here certainly makes a moyo on a grand scale, but Black's position at the top is too thin to support it, so White will have an easy time invading it. <= ]
))
)
