(;GM[1]FF[4]CA[UTF-8]AP[CGoban:3]ST[2]
RU[Japanese]SZ[19]KM[0.00]
PB[Black to play]AW[np][nq][pq][nr][or][qr][rs]AB[no][oo][mp][pp][qp][mq][qq][mr][rr]C[Black to play and kill the group (ko is okay)?]
;B[ps]C[This is the killing move]
(;W[qs]
;B[pr]C[This looks suicidal but...]
;W[os]
;B[pr]C[...black throws back inside]
(;W[ps]
;B[op]C[This threatens to fals the eye.]
;W[rq]
;B[sr]C[There is only one eye here.]
(;W[oq]
;B[rp])
(;W[sq]
(;B[oq]C[If black plays here now white might escape along the edge
depending on what is above.])
(;B[rp]
;W[ss]
;B[oq]C[White is dead.])))
(;W[op]C[White should actually play here not take the stone.]
;B[oq]C[Now it is a ko.]
;W[rq]C[If white plays this as a ko threat....]
(;B[pq]
;W[sr]
;B[ps]C[... Black can give up the ko and swap half the
group for the corner.])
(;B[sr]
;W[pq]C[If black answers the threat then Black needs a ko
threat elsewhere.])))
(;W[os]C[If white blocks this side]
;B[qs]C[Then black plays here and the white group is dead.]
(;W[pr]
;B[qs]
;W[rq]
;B[ss]
;W[sq]
;B[rp]
;W[ps]
;B[sp]
;W[rs]
;B[sr])
(;W[op]
;B[ss]
;W[pr]
;B[rq]
;W[rs]
;B[qs]))
(;W[op]C[This doesn't help either]
;B[qs]
;W[os]
;B[ss]
;W[pr]
;B[rq]
;W[rs]
;B[qs])
(;W[rq]C[This isn't fast enough]
;B[sr]
(;W[pr]
;B[rp]
(;W[op]
;B[qs])
(;W[qs]
;B[op]))
(;W[sq]
;B[pr]
(;W[ss]
;B[rr])
(;W[oq]
;B[qs])
(;W[os]
;B[oq]))))
