(;GM[1]FF[4]CA[UTF-8]AP[CGoban:3]ST[2]
RU[Japanese]SZ[19]KM[0.00]
GN[178ex]PB[Black to kill]AW[mo][no][lp][op][lq][mq][pq][nr][pr]AB[mn][nn][ko][lo][oo][po][kp][qp][kq][qq][kr][qr][ls]
(;B[os]C[Black cannot play here to stop two eyes.]
(;W[ps]
;B[ns]
;W[ms]
;B[mr]
;W[lr]
;B[np]
;W[ms]
;B[mp]
(;W[or]C[Most of the group survives.])
(;W[ks]C[Also alive.]))
(;W[np]C[White can try this too.]
;B[or]
;W[oq]
;B[ps]
;W[ll]C[White can play elsewhere now - it is already a live group.]
;B[mr]
;W[ns]
;B[qs]
;W[lr]))
(;B[ns]C[This is also no good.]
;W[os]
;B[np]
;W[mp])
(;B[np]C[Black will have to play on the inside.]
;W[mp]
;B[os]C[Now this play works.]
(;W[or]
;B[nq]C[Black has to play another stone inside to stop two eyes in the middle.]
;W[ps]
(;B[ns]C[This is also hard to see.]
;W[ms]
;B[mr]C[If White captures this stone then it is a snap-back.]
(;W[oq]
;B[ns]C[Dead.])
(;W[lr]
;B[mr]))
(;B[mr]C[This play fails.]
;W[oq]
;B[ns]
;W[lr]))
(;W[ps]C[White can try here instead.]
(;B[ns]C[Black plays here and still kills.]
;W[or]
;B[nq]
;W[ms]
;B[mr]
;W[oq]
;B[ns])
(;B[nq]C[However this Black play fails to kill.]
;W[ns]))
(;W[ms]C[This also fails for White.]
;B[ps]
(;W[lr]
;B[oq])
(;W[or]
;B[nq])
(;W[nq]
;B[or]))))
