(;GM[1]FF[4]CA[UTF-8]AP[CGoban:3]ST[2]
RU[Japanese]SZ[19]KM[0.00]
PB[Black to play]AW[pp][qp][rp][mq][nq][pq][rq][mr][or][pr][rr][ms]AB[po][qo][ro][lp][mp][np][op][sp][lq][oq][qq][sq][lr][qr][sr][ls][rs]C[Black to play and kill]
(;B[os]C[Often the play that threatens the snap-back is correct.]
;W[ps]C[But this reply stops the snap-back and traps two stones too.]
;B[ns]
;W[nr]
;B[ss]
;W[qs]C[White lives])
(;B[qs]C[Connecting here does not kill either]
;W[ps]
;B[ns]
;W[ss]
(;B[rs]
;W[nr])
(;B[nr]C[Capturing just four stones is not enough.]
;W[so]))
(;B[ps]C[This is sometimes a good shape.]
(;W[ns]C[If White plays here then it is dead.]
;B[qs])
(;W[os]
;B[nr]
;W[qs]
;B[ns]C[Again capturing four stones is not enough.]))
(;B[ns]C[This also does not work.]
;W[qs]
(;B[nr]
;W[os])
(;B[os]
;W[nr]))
(;B[nr]C[The self-atari is the play that kills.]
(;W[ns]
;B[ps]C[Now this stops the second eye]
;W[qs]
;B[qr])
(;W[os]
;B[qs])
(;W[qs]
;B[os]C[Now we get the snap-back]
;W[ns]
;B[nr])))
