(;AB[ab]AB[bb]AB[cc]AB[cd]AB[dd]AB[dc]AB[db]AB[eb]AB[ec]AB[de]AW[cb]AW[ba]AW[ac]AW[bc]AW[bd]AW[ad]AW[ce]AW[df]AW[ef]AW[ee]AW[ed]AW[fe]AB[fd]AB[gd]AB[ge]AB[ff]AB[fg]AW[eg]AW[dg]AW[cg]AW[bg]AW[ag]AW[af]AB[dh]AB[ch]AB[bh]AB[eh]AB[gh]AB[gb]C[Can black kill white unconditionally? Play ALIVE (G19) if you think White is alive no matter what. Play at KO (G17) if you think he can only kill with ko. If you think it's possible to kill unconditionally then do it.FORCE]LB[gc:KO]LB[ga:ALIVE]AP[goproblems]
(;B[be];W[bf]
(;B[ae];W[bd]C[ko])
(;B[cf]C[ko])
(;B[ca];W[ae]))
(;B[cf];W[be])
(;B[bf];W[aa]
(;B[be];W[ae]
(;B[cf];W[ce])
(;B[da];W[ca])
(;B[bb];W[ca]))
(;B[da];W[ca])
(;B[bb];W[ca]))
(;B[ca];W[be])
(;B[gc]C[];W[be]AB[ba]AW[ab]AW[bb]AB[cb]AW[db]AW[eb]AW[gb]AB[ac]AB[bc]AW[cc]AW[dc]AW[ec]AW[gc]AB[ad]AB[bd]AW[cd]AW[dd]AB[ed]AW[fd]AW[gd]AB[ce]AW[de]AB[ee]AB[fe]AW[ge]AB[af]AB[df]AB[ef]AW[ff]AB[ag]AB[bg]AB[cg]AB[dg]AB[eg]AW[fg]AW[bh]AW[ch]AW[dh]AW[eh]AW[gh]C[You think it is a ko. So the sides are swapped and now White tries to kill Black unconditionally; prove it cannot be done.]
(;B[bf];W[cf]C[Ko or not? Play at KO (F18) to simulate a ko threat, if you think you need one.]LB[fb:KO]
(;B[fb];W[fc]C[White has answered your threat, obviously.]
(;B[ae];W[ah])
(;B[aa];W[ce])
(;B[ce];W[ae]
(;B[bd];W[cf]C[Ko for life, so there is no unconditional kill. Well done.RIGHT])
(;B[ad];W[bd])
(;B[cf];W[ah]))
(;B[ca];W[ae]))
(;B[ae];W[ah])
(;B[aa];W[ce]C[One eye.])
(;B[ca];W[ae]))
(;B[ae];W[cf]MA[ab]MA[bb]C[You can get one eye, that's all.])
(;B[cf];W[ae])
(;B[aa];W[cf]C[One eye, unconditional death.])
(;B[ca];W[ae]))
(;B[ga]C[Sorry, Black can get a ko for life. See the KO variation.]))