(;GM[1]FF[4]CA[UTF-8]AP[CGoban:3]ST[2]
RU[Japanese]SZ[19]KM[0.00]
GN[177dx]PB[Black to kill]AW[nn][no][po][mp][pp][nq][oq][mr][ms][os]AB[mm][nm][om][pm][qn][lo][qo][lp][op][qp][lq][mq][rq][lr][nr][qr]
(;B[pq]C[This looks like the vital point in White's shape.]
;W[pr]
;B[oo]
;W[qq]
;B[on]
;W[rr]C[But this ends in a ko, which is not best for Black.]
;B[pq])
(;B[oo]C[This is the move that forces White and avoids the ko.]
;W[on]
;B[pq]C[Now Black can play here with atari.]
;W[np]
;B[or]C[White dies.]))
