(;GM[1]FF[4]CA[UTF-8]AP[CGoban:3]ST[2]
RU[Japanese]SZ[19]KM[0.00]
PB[Black to play]AW[ln][mo][op][pp][rp][lq][mq][nq][qq][sq][or][qr][qs][rs]AB[po][qo][ro][kp][qp][kq][pq][lr][mr][nr][pr][rr][sr][ps]C[This is the problem position. Black to play]
(;B[ns]C[This is the correct move - it allows the three
black stones to connect out, leaving the white
corner group dead.]
(;W[os]
;B[oq])
(;W[oq]
;B[os]))
(;B[oq]C[This is self-atari!])
(;B[os]
;W[ns]C[This is a snap-back shape.]
(;B[oq]
;W[or])
(;B[ms]C[This capture fails too.]
;W[oq]
;B[ns]
;W[kr]C[This way black is short of liberties.]))
(;B[so]
;W[os]C[Trying to capture the corner stones is too slow.]
;B[sp]
;W[oq]
;B[rq]C[Half the white stones escape.]))
