(;
GM[1]
SZ[19]
AW[cc][dc][ec][gc][hc][ic][oc][oj][ol][pn][po][pp][oq][np][eq][ip][ci][ei][gi]
AB[ce][fe][ed][hd][id][jd][ld][od][pc][qd][pq][qq][qp][qo][qm][ql][cp][do][ck][ek]
C[Problem 168. White to play.  

This is another after-the-fuseki problem. Where is the vital point for White to play ? ]
(;W[hk]
TE[2]
C[Correct Answer.  

The knight's move of White 1 is the vital point. With this move, White builds a moyo in the center and Black is now unable to use his thick wall above to attack White. ]
;B[fj]
C[If Black peeps at 2, ... ]
;W[ef]
C[... White defends by forcing with 3, ... ]
;B[dd];W[hh]
C[... then playing the diagonal move of 5. <= ]
)
(;W[gk]
LB[hk:@]
C[Failure.  

There is a big difference between White 1 and the knight's move at @ in the Correct Answer. ]
;B[fj]
TR[ck]
C[The double peep of Black 2, anchored by his marked stone, is now a strong move. ]
;W[ef];B[dd];W[hh]
LB[ef:3]
C[After White 3 and 5, ... ]
;B[gj]
C[... Black can cut through with Black 6 ... ]
;W[hj];B[hk]
C[... and Black 8. <= ]
)
(;W[fk]
C[Failure.  

Attaching with 1 only helps Black ... ]
;B[fl];W[gk];B[gl];W[hk];B[hl]
C[... to march into White's potential moyo with the sequence to 6. <= ]
)
(;W[fo]
C[Failure.  

Although White 1 is often a good move, in this case it is too small in scale. ]
;B[gk];W[ii];B[ik];W[ki];B[kk]
C[Black advances into White's sphere of influence with the sequence to 6 while using his thickness to maintain the pressure on White. <= ]
)
)