(;GM[1]FF[4]CA[UTF-8]AP[CGoban:3]ST[2]
RU[Japanese]SZ[19]KM[0.00]
AW[bp][cp][dp][ep][eq][dr][fr]AB[aq][bq][cq][dq][fq][gq][ar][er][gr][as]
(;B[fs]C[If Black takes the stone in atari immediately, White can capture or at least turn this in to a ko fight the life of the Black stones.]
;W[cr]
(;B[ds]C[In this line, White captures without ko.]
;W[bs]
(;B[br]
;W[ap])
(;B[es]
;W[ap])
(;B[cs]
;W[es]
(;B[fr]
;W[ap])
(;B[ds]C[(In case you are wondering, this recapture is legal in BGA rules: it repeats a position, but now it's White to play instead of Black.)]
;W[ap])))
(;B[br]C[Also in this line, White captures without ko.]
;W[ap]
;B[cs]
;W[bs])
(;B[cs]C[Black can make this a ko to rescue his stones, but will suffer a loss somewhere in ignoring a ko threat to do so.]
;W[ds]
(;B[bs]C[Just defending the stone doesn't work.]
;W[ap]
;B[es]
;W[br])
(;B[br]C[Here is the ko.]
;W[bs]C[White takes the ko.]
;B[ss]C[Black makes a ko threat somewhere.]
;W[rr]C[If White responds ...]
;B[cs]C[Black retakes the ko.]
;W[qq]C[White makes a ko threat.]
;B[es]C[Black can win the ko and rescue his stones, but only by sustaining a loss from ignoring White's threat.])))
(;B[es]C[This is the solution.]
(;W[cr]C[If White tries the same line as before ...]
;B[cs]
;W[ds]C[This time, White does not have enough liberties to play this]
;B[br])
(;W[ds]C[What if White tries to use this atari?]
;B[fs]
;W[cr]
;B[br]C[White runs out of liberties.]
(;W[ap]
;B[cs])
(;W[bs]C[Ko?]
;B[cs]C[There's no ko here!]))))
