(;CA[gb2312]AP[MultiGo:4.4.4]SZ[19]AW[pq][op][no][mo][lp][lq][mq][nr][pr]AB[qr][qq][qp][po][oo][nn][mn][lo][kp][kq][kr][ls]C[Black to play and kill]
(;B[np]C[This is the correct first play];W[mp]
;B[os]C[This is the key play of the solution]
(;W[or]C[This threatens to make to eyes but does not threaten the edge stone.];B[nq];W[ps];B[ns];W[ms];B[mr];W[oq];B[ns])
(;W[ms]C[The edge stone can escape and leave one eye false.];B[ps];W[nq];B[or];W[lr];B[oq])
(;W[nq]C[Again the edge stone can false the eye then escape.];B[or];W[ms];B[ps];W[lr];B[oq]))
(;B[os]C[Playing the key play first does not work as white can make good shape higher up.];W[np];B[or]
;W[oq]C[White lives]))
