(;
GM[1]
SZ[19]
AW[dd][jc][ri][qj][pj][pi][ni][ok][dp][fq][iq][jq][kq][mq][mp]
AB[pd][pg][ng][qh][pk][qk][qm][pq][op][mo][no][lp][kp][jp][ho]
TR[ho][jp][kp][lp][mo][no][ni][ok][pj][pi]
TR[qj][ri]
C[Problem 77. Black to play.  

Note the thick black wall (the marked stones) at the bottom. How should Black attack the marked white ones ? ]
(;B[lh]
TE[2]
C[Correct Answer.  

Black drives White into his thick wall at the bottom with the knight's moves of 1 ... ]
;W[lj];B[ji]
C[... and 3. ]
;W[ol];B[pm];W[jk]
C[After 6, White can probably live, but Black gets influence in the center, giving him a huge advantage at the top. ]
;B[hc]
C[Black now uses his advantage by invading at 7. ]
;W[je];B[he];W[mc]
C[White extends to 10, but ... ]
;B[nb]
C[... Black plays the vital point of 11, ... ]
;W[jg];B[if]
C[... then confines the white stones at the top with 13 ... ]
;W[jf];B[ih]
LB[df:A]
C[... and 15. White will live in gote, but, in the process, Black will be able to strengthen his corner. With this sente, Black will next play A. <= ]
)
(;B[li]
C[Failure.  

The cap of Black 1 drives the white stones in the wrong direction. ]
;W[mh];B[kg];W[mg]
C[After 4, White's stones should have no trouble making two eyes. <= ]
)
)