(;
GM[1]
SZ[19]
AW[cc][dp][eq][er][fp][fo][fn][fl][fj][jq][lp][op]
AB[cq][cp][cn][hk][hm][go][gp][gq][fq][jo][qp][qn][qc]
C[Problem 167. White to play.  

In the lower left corner, Black and White both advanced into the center. However, White ended in sente. How should she play now so as take control of the game ? ]
(;W[cl]
LB[ck:B][bo:A]

TE[2]
C[Correct Answer.  

White 1 is a strong move that takes control of the left side and threatens the black stones with a peep at A. An extension to Black B would be a very big move. ]
;B[cm]
C[Black has to defend with 2, ... ]
(;W[dl]
LB[bl:A]
C[... forcing White to strengthen her stones with 3. Instead of 3, White could also descend to A. <= ]
)
(;W[bl]
LB[dl:@]
C[Black's bad aji.  

Descending with White 3 (suppose a White stone at @) is sente against the black stones in the corner. If Black ignores this move, ... ]
;B[jj]
C[(Black 4 is played to get 'White to move'.) ]
;W[br]
C[... White will play 5 ... ]
;B[cr];W[bo]
C[... and 7, and Black's stones are dead. <= ]
))
(;W[hi]
C[Failure.  

With respect to the black stones in the center, White 1 is certainly a big point, but Black will ignore it ... ]
;B[ck]
C[... and extend to 2. There is a big difference between this diagram and the Correct Answer. Here, Black has expended his territory on the left, leaving the white stones thin. <= ]
)
)