(;GM[1]FF[4]CA[UTF-8]AP[CGoban:3]ST[2]
RU[Japanese]SZ[19]KM[0.00]
PB[Black to play]C[Just play through the moves to move 30 which is the problem position. These do not represent a game sequence!]
;B[br]
;W[cr]
;B[bq]
;W[cq]
;B[bp]
;W[cp]
;B[bo]
;W[dp]
;B[cn]
;W[do]
;B[dn]
;W[eo]
;B[en]
;W[fo]
;B[fn]
;W[fp]
;B[gn]
;W[fq]
;B[go]
;W[er]
;B[gq]
;W[fs]
;B[gr]
;W[]
;B[fr]
;W[]
;B[hr]
;W[]
;B[ep]
;W[]C[This is the problem position. Black to play.]
(;B[ds]C[This looks like a place to falisfy white's eye on the edge.]
;W[cs]
;B[es]
;W[dr]C[However white has 2 ways to make a second eye.]
(;B[eq]
;W[es])
(;B[es]
;W[eq]))
(;B[es]
;W[ds]C[This doesn't work as white's shape is alive.])
(;B[dq]
;W[eq]
;B[ds]
;W[dr]C[This way is too easy.])
(;B[eq]C[This is correct: sacrificing a second stone]
(;W[dq]
;B[ds]C[Now this move really does stop the eye on the
edge and there can only be 1 eye above.])
(;W[es]C[If white connects here]
;B[cs]
;W[ds]
;B[dq]C[Then the hane followed by sacrificing a third
stone leaves the white group with dead shape.])
(;W[cs]C[If white drops to the edge]
;B[es]C[Then this throw-in is the killing move.]
(;W[ds]
;B[dq])
(;W[dq]
;B[ds]
;W[dr]
;B[es]))))
