(;GM[1]FF[4]CA[UTF-8]AP[CGoban:3]ST[2]
RU[Japanese]SZ[19]KM[0.00]
PB[Black to play]AW[kn][mn][ko][mo][lp][mp][mq][oq][pq][mr]AB[kl][ll][ml][jm][nm][jn][nn][jo][lo][no][qo][kp][op][pp][jq][lq][qq][lr]C[This is the problem position. Black to play]
(;B[qr]C[The descent is the strongest way for black to
stop white making two edge eyes.]
(;W[os]C[This move often makes eyes.]
;B[ms]
;W[pr]
;B[nr]C[This stops two edge eyes.]
;W[ns]
;B[nq]
;W[np]C[But now surely that is two eyes?]
;B[ln]C[Here's the clever sacrifice.]
;W[lm]C[White has to take as he was in atari.]
;B[ln]C[Now the trow in leaves white with a false 
eye or worse short of liberties.]
;W[lo]
;B[mm]C[White cannot back a real eye here through shortage of liberties.]
;W[km]
;B[ln])
(;W[pr]C[If white playes here]
;B[ps]
;W[os]
;B[nq]
;W[qs]
;B[nr]
;W[np]
;B[ln]
;W[lm]
;B[ln]C[Still miai to kill one of the eyes]
(;W[mm]
;B[km]
;W[lo]
;B[ms]C[Atari])
(;W[rr]
;B[rq]C[White cannot get an eye in the corner.])))
(;B[nr]C[If black starts here then white can still make an edge
eye but without the liberty shortage on the top eye.]
;W[nq]
(;B[ms]
;W[os]
;B[ns]
;W[or]
;B[ls]
;W[qr]C[Lot's of eyes])
(;B[qr]
;W[or]C[One edge eye - but with lots of liberties.])))
