(;GM[1]FF[4]CA[UTF-8]AP[CGoban:3]ST[2]
RU[Japanese]SZ[19]KM[0.00]
GN[177ex]PB[Black to kill]AW[pp][qp][rp][nq][rq][nr][or]AB[mn][on][pn][qn][ro][mp][np][mq][oq][mr][rr]
(;B[pq]C[Black can try this push.]
;W[pr]C[This is one of White's options.]
(;B[op]
;W[qr]C[But White safely seals off the corner.])
(;B[qr]C[If black tries this way he will lose the race.]
;W[op]
;B[qq]
;W[sr]
;B[rs]
;W[sq]))
(;B[qr]C[This also fails]
;W[pr]C[This is one of several possible responses.]
;B[pq]C[This is a shape already seen above.])
(;B[pr]C[This is the vital point in White's shape.]
(;W[pq]
(;B[ns]C[However Black should not play here as only three white stones die.]
;W[qr]
;B[os]
;W[qs]C[White lives in the corner.])
(;B[ps]C[This is the correct play to kill White.]
;W[qr]
;B[rs]C[Again Black plays the same shape as before and the four black stones cannot be captured by White.]
;W[op]
;B[ns]C[White is dead.]))
(;W[qr]C[If White tries this way...]
;B[pq]C[...Black must take this vital point. There is not enough room for White to live in the corner.])))
