(;LB[br:0]LB[cr:1]C[Please choose a number: 0 or 1.FORCE]AB[ao]AB[bo]AB[co]AB[do]AB[eo]AB[go]AB[fo]AB[ho]AB[hp]AB[hq]AB[hr]AB[hs]AP[goproblems] (;B[br]C[]AB[ar]AB[cr]AB[dr]AB[gq]AB[gp]AW[aq]AW[bq]AW[cq]AW[dq]AW[er]AW[fs]AW[gs]AW[gr]AW[fq]AW[fp]AW[ep]AB[dp]AB[cp]AW[bp];W[ds]C[White has no ko threats. How should you play?] (;B[bs]C[Only seki. You could have killed white.]) (;B[cs];W[bs] (;B[as];W[bs]C[:O]) (;B[es]C[White has no ko threats - you win.RIGHT]MA[ds];W[eq];B[fr]C[RIGHT])) (;B[as];W[cs]C[:(]) (;B[ap]C[NOTTHIS];W[eq] (;B[bs]C[Only seki. You could have killed white.]) (;B[cs];W[bs];B[es]MA[ds]C[White has no ko threats - you win.RIGHT];W[in]C[(Ko fight: please play at K)FORCE]LB[io:K];B[io];W[ds]MA[es]C[Playing at A4 first forced white to use a big ko threat ... but it's a ko fight nonetheless.]))) (;B[cr]AB[ar]AB[br]AB[dr]AB[gq]AB[gp]AB[cp]AB[dp]AW[gs]AW[gr]AW[fs]AW[er]AW[fq]AW[fp]AW[ep]AW[dq]AW[cq]AW[bq]AW[aq]AW[bp];W[ds]C[White has one good ko threat. How should you play?] (;B[cs];W[bs] (;B[as];W[bs]C[:O]) (;B[es];W[in]LB[io:K]C[(Ko fight: please play at K)FORCE];B[io];W[ds]MA[es]C[:(])) (;B[as];W[cs]C[:(]) (;B[bs]C[Seki. You live in the corner, and have a ko threat at A4.RIGHT]) (;B[ap];W[eq] (;B[cs];W[bs];B[es];W[in]C[(Ko fight: please play at K)FORCE]LB[io:K];B[io];W[ds]MA[es]C[Playing at A4 first forced white to use a big ko threat ... but it's a ko fight nonetheless.]) (;B[bs]C[Seki ... but you wasted a ko threat at A4.]))))