(;GM[1]FF[4]CA[UTF-8]AP[CGoban:3]ST[2]
RU[Japanese]SZ[19]KM[0.00]
PB[Black to play and kill]AW[qp][nq][oq][pq][qq][rq][or]AB[rn][po][qo][lp][np][op][rp][mq][lr][nr][pr]
(;B[os]C[It seems natural for black to connect out and is the correct first move.]
;W[ps]C[White normally throws in to gain speed.]
;B[qs]
(;W[qr]
;B[sr]C[Black has to play here to stop white taking the vital eye-making 2-1 point.]
;W[rs]
;B[sq]
;W[rr]
;B[ps]C[Black now makes a four-stone sacrifice.]
;W[ns]
;B[ps]C[But it is only one eye.]
;W[mr]C[This looks like a second eye...]
;B[ls]C[... but black calmly descends to the edge and despite capturing the stone this isn't an eye for white either.]
;W[ms]
;B[os])
(;W[rs]C[If white plays the 2-1 point...]
;B[sr]C[...then black must play the other.]
;W[sp]
;B[ns]
;W[ro]C[Again capturing this stone looks like an eye...]
;B[sn]C[... but again black calmly descends to the edge.]
;W[qr]
;B[ps]
;W[so]
;B[sq]C[White is still dead.]))
(;B[qr]C[If black tries this ]
;W[os]C[White calmly blocks]
;B[rr]
;W[sq]
;B[sr]
;W[rs]C[White will capture the four stones making two eyes.]
;B[ns]
;W[qs]
;B[pp]
;W[ps])
(;B[rr]C[This black is harder to read out.]
(;W[sq]C[This white might fail...]
;B[os]
;W[ps]
;B[qs]
;W[qr]
(;B[ps]
;W[rs]
;B[ss]
;W[sr]C[White will live this way.])
(;B[rs]
;W[ps]C[Or get a ko.]
;B[ns]
;W[sr]
;B[pr]))
(;W[sr]C[If white plays here it looks impossible for black.]
(;B[qr]
;W[rs]
;B[os]
;W[ps])
(;B[os]
;W[qr]
;B[rs]
;W[ps])))
(;B[qs]
;W[os]
;B[sr]
;W[sq]C[White has outside liberties so easily lives]))
