(;GM[1]FF[4]CA[UTF-8]AP[CGoban:3]ST[2]
RU[Japanese]SZ[19]KM[0.00]
PB[Black to play and win the capturing race]
AW[pn][rn][qo][so][qp][rp][nq][oq][pq][or][qr][os]
AB[no][po][np][pp][sp][mq][qq][rq][sq][mr][pr][sr][qs]
C[This is from the Nihon Ki-in playing cards]
(;B[rr]C[Black can try taking the stone]
;W[ps]
;B[nr]
;W[qr]C[Black needs a big ko threat]
;B[qm]C[Say this is one (it probably isn't)]
;W[qn]
;B[pr]
;W[ss]
;B[ns]
;W[qr]C[And he now needs a second one])
(;B[nr]C[If black fills an outside liberty...]
(;W[ps]C[... then this must be wrong for white]
;B[rs]
;W[pr]
;B[ns])
(;W[rs]C[This must be better foe white]
;B[rr]
;W[ps]
;B[ss]
;W[qr]C[And black needs a ko threat again, and it is two
stage for him.]))
(;B[rs]C[As seen before this is the shape that causes white to fail.]
;W[ps]
;B[nr]
;W[pr]
;B[ns]C[Now white cannot atari black because of his eye in the corner.]))
