(;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[op][pp][qp][nr][or][qr][rr][sr]AB[rn][oo][po][qo][np][rp][lq][nq][rq][sq][mr][ms]
(;B[ps]C[This may look like the vital point for White's eye shape, but White easily lives.]
;W[pr]
;B[ns]
;W[os])
(;B[qq]C[This also fails and the three white stones are not in danger.]
;W[pr])
(;B[pr]C[This is a tricky move to defend against.]
;W[pq]C[White can capture it with two eyes this way.]
;B[ps]
(;W[qs]
;B[oq]
;W[qq]
;B[ns]
;W[os])
(;W[os]
;B[oq]
;W[qs]
;B[pr]
;W[qq]))
(;B[rs]C[This is a good move to destroy White's eye shape.]
(;W[ns]C[If White plays this defence...]
;B[pr]C[... now the wedge works.]
;W[pq]
;B[ps]
;W[qs]
;B[qq]
;W[os]
;B[pr]C[After this throw-in White is dead.])
(;W[qq]C[If White connects here...]
;B[oq]C[... this push reduces the eye space.]
;W[pr]
;B[ns])
(;W[qs]C[If White makes the corner eye... ]
;B[pr]C[... then the wedge kills again.]
;W[pq]
;B[qq]
;W[ps]
;B[ns]
(;W[os]
;B[oq])
(;W[oq]
;B[os]))
(;W[oq]C[If the connection is this side...]
;B[qq]C[... then again the push kills.]
;W[pq]
;B[os]
;W[ps]
;B[ns])
(;W[pq]C[If White threatens eye shape this way...]
;B[ns]C[.. then this edge push leaves the eye false.]
;W[os]
;B[qq]
;W[qs]
;B[pr]
;W[ps]
;B[oq])
(;W[ps]C[Also this move fails to live.]
(;B[ns]
(;W[oq]
;B[qq]
;W[pq]
;B[os])
(;W[os]
;B[oq]
;W[pq]
;B[qq]))
(;B[pq]
;W[ns]
;B[pr]))))
