(;GM[1]FF[4]CA[UTF-8]AP[CGoban:3]ST[2]
RU[Japanese]SZ[19]KM[0.00]
PB[Black to play]AW[nn][on][mo][po][mp][np][pp][pq][or][qr][os][qs]AB[nm][om][pm][mn][qn][lo][qo][lp][qp][mq][qq][lr][nr][rr][ns][rs]C[This is the problem position. Black to play]
(;B[nq]C[If black just pushes in...]
;W[oq]C[... white makes two eyes.])
(;B[pr]C[If white tries this throw in....]
;W[oq]C[... then white simply connects threatening two eyes
without the two stones in atari.]
(;B[oo]
;W[ps]
;B[nq]
;W[pn]C[Alive])
(;B[ps]
;W[oo]C[Also alive,]))
(;B[oo]
;W[nq]C[Any inside move allows two easy eyes, apart 
from one move....])
(;B[oq]C[This is the killer move threatening a snapback shape.]
(;W[nq]
;B[pr]
(;W[op]
;B[ps]C[Dead])
(;W[ps]
;B[pr]C[Snapback.]))
(;W[pr]C[If white stops the snapback...]
;B[op]C[... then black plays another move inside 
and white cannot capture those two stones
and fails to make a second eye.]
(;W[oo]
;B[nq]C[False eye])
(;W[nq]C[Self-atari!]
;B[no]))
(;W[op]
;B[pr]C[Still a snapback shape.])))
