(;GM[1]FF[4]CA[UTF-8]AP[CGoban:3]ST[2]
RU[Japanese]SZ[19]KM[0.00]
PB[Black to play]AW[kq][nq][oq][pq][kr][mr][pr][ls][ms][ps]AB[mp][np][op][pp][qp][lq][mq][qq][lr][nr][qr]
(;B[ns]C[Black may try the atari]
;W[ks]
;B[qs]C[When Black blocks on the outside this is now a seki.]
(;W[or]
;B[os])
(;W[kp]
;B[or]
;W[os]
;B[nr]
;W[ns]))
(;B[qs]C[If Black plays here then White just plays atari on the white stone from the edge.]
;W[ns])
(;B[os]C[This is the correct move. White cannot atari without it
being self-atari.]
(;W[ns]
;B[ks])
(;W[or]
;B[qs])
(;W[ks]C[White must play here first...]
;B[qs]C[... but Black fills this liberty and White is soon captured.]
;W[ns]
;B[or])))
