(;AB[bp]AB[cp]AB[dp]AB[eq]AB[fr]AB[gr]AB[gq]AB[hp]AB[ho]AB[hn]AB[hm]AB[iq]AB[ir]AB[fl]AW[bo]AW[co]AW[do]AW[ep]AW[fq]AW[fp]AW[gp]AW[go]AW[gn]AW[fn]AW[en]AW[dm]AW[bl]C[Beware of ko...]AP[goproblems] (;W[dq];B[er] (;W[bq];B[cq] (;W[cr];B[ap] (;W[dr];B[br] (;W[ar];B[aq] (;W[bs];B[as]C[White now has to win a two stage ko.]) (;W[ao];B[as])) (;W[ao];B[aq]) (;W[bs];B[ar])) (;W[br];B[dr]) (;W[aq];B[dr]) (;W[ao];B[dr]) (;W[ar];B[dr]) (;W[bs];B[dr])) (;W[ap];B[cr]C[White can squeeze Black even tighter than this.]) (;W[dr];B[aq]) (;W[br];B[ap]) (;W[aq];B[ap]) (;W[ao];B[ap]) (;W[ar];B[ap])) (;W[cq];B[bq]) (;W[cr];B[cq] (;W[dr];B[br]) (;W[ap] (;B[dr]C[CHOICE] (;W[bq]C[White squeezes the corner away from Black.RIGHT]) (;W[br];B[aq]) (;W[aq];B[br]) (;W[ar];B[br]) (;W[ao];B[aq]) (;W[ds];B[aq]) (;W[cs];B[aq]) (;W[bs];B[aq]) (;W[as];B[aq])) (;B[bq]C[In the endgame this is the best way for Black to continue.CHOICE] (;W[br];B[dr] (;W[aq]C[];B[dq]C[This is what Black would play in the endgame. Next, C1 is a 5 point gote move for both.RIGHT] (;W[cs]C[White has secured 4 points and can get a further point per move by playing D1, E1 etc. until Black drops the lid on that.RIGHT]MA[ar]MA[as]MA[bs]MA[ao]TR[ds]) (;W[ds];B[ar] (;W[as];B[cs] (;W[bs];B[es] (;W[ao];B[cs];W[ar]C[No territory at all in the corner.]) (;W[ar];B[cs];W[ao]C[No territory at all in the corner.])) (;W[ao];B[es]) (;W[ar];B[es])) (;W[ao];B[bs]C[Ko]) (;W[cs];B[ao]) (;W[bs];B[ao]))) (;W[ar]MA[aq]MA[cs]C[White connects the stones, but this is gote and at least one point worse than wA3, bD3, wC1.]MA[dq]) (;W[as];B[aq]) (;W[bs];B[aq]) (;W[cs];B[aq]) (;W[ds];B[aq])) (;W[aq];B[br] (;W[ar];B[bs]) (;W[dr];B[ar] (;W[ao];B[ds]) (;W[bs];B[ao]) (;W[as];B[ao]) (;W[cs];B[ao]) (;W[ds];B[ao])) (;W[bs];B[dr] (;W[ar];B[cs]) (;W[cs];B[ar]) (;W[as];B[cs]) (;W[ao];B[ar])) (;W[ao];B[ar]) (;W[cs];B[ar] (;W[dr];B[ao]) (;W[ao];B[dr]) (;W[bs];B[ao]) (;W[as];B[ao]))) (;W[dr];B[br] (;W[aq];B[ar] (;W[ao];B[ds]) (;W[bs];B[ao]) (;W[as];B[ao]) (;W[cs];B[ao]) (;W[ds];B[ao])) (;W[ar];B[bs]) (;W[bs];B[ar])) (;W[ar];B[br] (;W[bs];B[dr] (;W[cs];B[ds] (;W[aq];B[as]) (;W[as];B[aq]) (;W[ao];B[as])) (;W[aq];B[cs]) (;W[as];B[cs]) (;W[ao];B[cs]) (;W[ds];B[cs]C[A ko by which White has nothing to gain (Black can play E1 to end it); also Black has an internal ko threat at D3.]MA[es]MA[dq])) (;W[aq];B[bs]) (;W[dr];B[bs]) (;W[ao];B[bs]) (;W[cs];B[bs]) (;W[as];B[bs])))) (;W[br];B[dr] (;W[ap];B[aq]) (;W[bq];B[ao]) (;W[aq];B[ap]) (;W[ar];B[ao]) (;W[ao];B[ap])) (;W[bq];B[ap] (;W[dr];B[br] (;W[ar];B[aq] (;W[bs];B[as]C[White now has to win a two stage ko.]) (;W[ao];B[as])) (;W[ao];B[aq]) (;W[bs];B[ar])) (;W[br];B[dr]) (;W[aq];B[dr]) (;W[ao];B[dr]) (;W[ar];B[dr]) (;W[bs];B[dr])) (;W[aq];B[ap] (;W[dr];B[br] (;W[ao];B[bq];W[bs];B[ar]) (;W[bq];B[ar]) (;W[ar];B[cs]) (;W[bs];B[ds]) (;W[cs];B[bs]) (;W[ds];B[es])) (;W[bq];B[dr]) (;W[ao];B[dr]) (;W[br];B[dr])) (;W[ao];B[ap] (;W[dr];B[br] (;W[aq];B[bq];W[bs];B[ar]) (;W[bq];B[aq]) (;W[ar];B[cs]) (;W[bs];B[ds])) (;W[br];B[dr]) (;W[aq];B[dr]) (;W[bq];B[dr])) (;W[ar];B[aq] (;W[dr];B[br] (;W[bs];B[as]C[Two-stage ko.]) (;W[ap];B[ao];W[bs];B[as]C[Two stage ko, and White just wasted a ko threat.]) (;W[ao];B[cs])) (;W[br];B[dr]) (;W[ap];B[ao] (;W[dr];B[br];W[bs];B[as]C[Two stage ko, and White just wasted a ko threat.]) (;W[br];B[dr]) (;W[bq];B[br]) (;W[an];B[dr])) (;W[bq];B[br])) (;W[bs];B[dr]) (;W[cs];B[dr])) (;W[dr];B[br]C[Nice solid corner.]) (;W[br];B[cq]) (;W[ap];B[cr] (;W[br];B[cq]C[Nice, but you can squeeze Black even tighter.]) (;W[bq];B[cq]C[Nice, but you can squeeze Black even tighter.]) (;W[cq];B[bq] (;W[br];B[dr];W[aq]C[Not good enough.]) (;W[aq];B[br]) (;W[ar];B[br])) (;W[aq];B[br]) (;W[ar];B[br]) (;W[bs];B[bq]) (;W[dr];B[br])) (;W[aq];B[br]) (;W[ar];B[br] (;W[cr];B[bq]) (;W[dr];B[cr]) (;W[bq];B[cq]) (;W[cq];B[bq]) (;W[ap];B[bq]) (;W[aq];B[ap]) (;W[bs];B[aq] (;W[cr];B[as]C[Don't bother to find a ko threat; ko would be a success for Black.] (;W[cs];B[cq] (;W[ao];B[ap]) (;W[ap];B[ao]) (;W[ar];B[dr])) (;W[bq];B[cs]) (;W[dr];B[ar];W[cq]) (;W[cq];B[cs]) (;W[ao];B[cs]) (;W[ap];B[cs]) (;W[ar]C[NOTTHIS])) (;W[cq];B[cr]) (;W[dr];B[cs]) (;W[cs];B[cq]) (;W[ao];B[cs]) (;W[ds];B[dr])) (;W[cs];B[aq])) (;W[bs];B[cq]) (;W[cs];B[cq]) (;W[ds];B[cq]) (;W[as];B[ap]) (;W[ao];B[cq])) (;W[er];B[dq]) (;W[dr];B[dq] (;W[ap];B[aq]) (;W[er];B[cr]) (;W[cr];B[er]) (;W[cq];B[er]) (;W[bq];B[ap])) (;W[bq];B[cq] (;W[cr];B[br] (;W[dr];B[er] (;W[dq];B[aq]) (;W[bs] (;B[aq]) (;B[ar] (;W[dq];B[aq]) (;W[ap];B[dq]))) (;W[aq];B[ap])) (;W[er];B[dq] (;W[dr];B[aq] (;W[ao]) (;W[bs];B[ar] (;W[ao];B[ap];W[cs];B[es]) (;W[cs];B[es]) (;W[es];B[cs]))) (;W[ap];B[aq];W[dr];B[ao])) (;W[ap];B[aq];W[er];B[dq];W[dr];B[ao])) (;W[dr];B[br] (;W[er];B[dq];W[cr];B[aq] (;W[ao]) (;W[bs];B[ar] (;W[ao];B[ap];W[cs];B[es]) (;W[cs];B[es]) (;W[es];B[cs]))) (;W[dq];B[er] (;W[ap];B[aq] (;W[cr];B[ao]) (;W[ao];B[cr])) (;W[cr];B[aq])) (;W[cr];B[er] (;W[dq];B[aq]) (;W[bs] (;B[aq]) (;B[ar] (;W[dq];B[aq]) (;W[ap];B[dq]))) (;W[aq];B[ap])) (;W[ap];B[aq];W[er];B[dq];W[cr];B[ao]) (;W[aq];B[ap] (;W[er];B[dq];W[cr];B[ar]) (;W[dq];B[er];W[cr];B[ar]))) (;W[ap];B[br] (;W[aq];B[ar] (;W[er];B[dq] (;W[cr];B[ao]) (;W[ao];B[dr])) (;W[cr];B[ao]) (;W[dr];B[er])) (;W[er];B[dq];W[cr];B[aq];W[dr];B[ao])) (;W[er];B[dq] (;W[ap];B[br];W[cr]) (;W[cr];B[br] (;W[dr];B[aq] (;W[ao]) (;W[bs];B[ar] (;W[ao];B[ap];W[cs];B[es]) (;W[cs];B[es]) (;W[es];B[cs]))) (;W[ap];B[aq];W[dr];B[ao])) (;W[dr];B[br];W[cr]))) (;W[cq];B[dq]) (;W[cr];B[dr]) (;W[br];B[dr]) (;W[ap];B[cq] (;W[bq];B[br] (;W[aq];B[ar] (;W[er];B[dq] (;W[cr];B[ao]) (;W[ao];B[dr])) (;W[cr];B[ao]) (;W[dr];B[er])) (;W[er];B[dq];W[cr])) (;W[dr];B[er] (;W[bq];B[br] (;W[cr];B[aq] (;W[dq];B[ao]) (;W[ao];B[dq])) (;W[dq];B[aq] (;W[cr];B[ao]) (;W[ao];B[cr])) (;W[aq];B[ar]) (;W[ar];B[aq]MA[cr]C[Black can either fight the ko or connect.];W[dq];B[ao]) (;W[bs];B[aq]) (;W[ao];B[aq])) (;W[cr];B[br] (;W[bq];B[aq] (;W[dq]) (;W[ao];B[dq])) (;W[aq];B[ar] (;W[dq];B[bq] (;W[ao];B[ds]) (;W[bs];B[ao]) (;W[as];B[ao]) (;W[cs];B[ao]) (;W[ds];B[ao])) (;W[ao];B[bq]) (;W[bs];B[dq])) (;W[ar];B[bs] (;W[dq];B[bq]) (;W[bq];B[aq]C[If Black cannot win the ko the connection at A is good enough. If White plays B instead of the ko then Black connects the ko; White A does not work..]LB[ao:B]LB[dq:A]) (;W[aq];B[bq])) (;W[bs] (;B[aq]) (;B[ar] (;W[dq];B[bq]) (;W[bq];B[dq]) (;W[aq];B[dq]))) (;W[dq];B[bq] (;W[aq]) (;W[ar];B[bs]) (;W[bs];B[ar]))) (;W[br];B[aq]) (;W[aq];B[br] (;W[bq];B[ar]) (;W[ar];B[bs]) (;W[cr];B[ar] (;W[dq];B[bq]) (;W[ao];B[bq]) (;W[bs];B[dq])) (;W[dq];B[ar]) (;W[cs];B[ar]) (;W[ds];B[ar]) (;W[bs];B[ar])) (;W[ar];B[br] (;W[cr];B[bs] (;W[dq];B[bq]) (;W[bq];B[aq]C[If Black cannot win the ko the connection at A is good enough. If White plays B instead of the ko then Black connects the ko; White A does not work..]LB[ao:B]LB[dq:A]) (;W[aq];B[bq])) (;W[bs];B[cs]) (;W[bq];B[aq]MA[cr]C[Black can either fight the ko or connect.];W[dq];B[ao]) (;W[dq];B[ds]) (;W[aq];B[bs]) (;W[cs];B[bs]) (;W[ds];B[bs])) (;W[dq];B[cr]) (;W[cs];B[aq]) (;W[ds];B[aq]) (;W[bs];B[aq])) (;W[er];B[dr] (;W[dq];B[aq] (;W[eq];B[br]) (;W[es];B[eq]C[Ko]) (;W[cr];B[eq]C[Ko]) (;W[ao];B[es]) (;W[ds];B[eq]C[Ko]) (;W[br];B[es])) (;W[bq];B[br];W[dq];B[aq]) (;W[br];B[aq] (;W[dq];B[es]) (;W[es];B[dq]) (;W[ao];B[bq] (;W[dq];B[es]) (;W[es];B[dq])) (;W[cr];B[es]) (;W[bq];B[ao] (;W[dq];B[es]) (;W[es];B[dq]) (;W[an];B[ap] (;W[dq];B[es]) (;W[es];B[dq]) (;W[cr];B[es])))) (;W[es];B[dq]MA[aq]C[Instead of connecting at D3 Black might well allow the ko fight by playing A3.]) (;W[aq];B[br] (;W[dq];B[es]) (;W[es];B[dq]) (;W[ar];B[es]) (;W[bq];B[ar])) (;W[ar];B[br] (;W[dq];B[es]) (;W[es];B[dq]) (;W[bs];B[cs] (;W[es];B[dq]) (;W[dq];B[as] (;W[es];B[aq]) (;W[eq];B[aq]) (;W[aq];B[es]) (;W[ds];B[es] (;W[bs];B[eq]) (;W[aq];B[eq]))) (;W[aq];B[es]) (;W[bq];B[as]TR[ar]TR[bq]C[The marked stones are captured with double ko.])) (;W[aq];B[es])) (;W[cr];B[br] (;W[dq];B[cs] (;W[es];B[aq]) (;W[eq];B[es]) (;W[aq];B[es])) (;W[cs];B[es]) (;W[es];B[aq] (;W[dq];B[cs]) (;W[cs];B[bs]) (;W[ds];B[cs]))) (;W[cs];B[aq] (;W[es];B[dq] (;W[ds];B[br] (;W[cr];B[ao]) (;W[bs];B[ar] (;W[cr];B[ao]) (;W[ao];B[fs])) (;W[ar];B[ao] (;W[an];B[bs]) (;W[cr];B[bs]) (;W[bs];B[cr])) (;W[ao];B[bs])) (;W[br];B[ds]) (;W[ao];B[ds]) (;W[ar];B[ao] (;W[ds];B[bs] (;W[br];B[cr]) (;W[cr];B[br]) (;W[an];B[br])) (;W[br];B[ds]) (;W[an];B[ds]))) (;W[ao];B[es]) (;W[dq];B[es]) (;W[cr];B[es]) (;W[ds];B[es]) (;W[br];B[es])) (;W[bs];B[aq] (;W[dq];B[es]) (;W[es];B[dq] (;W[ds];B[fs];W[cs];B[br]) (;W[ar];B[ao] (;W[ds];B[fs];W[cs];B[br]) (;W[br];B[ds]) (;W[cr];B[ds]) (;W[cs];B[ds]) (;W[an];B[ds])) (;W[ao];B[ds]) (;W[br];B[ds])) (;W[ao];B[es])) (;W[ds];B[es]MA[aq]C[Instead of capturing at E1 Black could also allow the ko fight by playing A3])) (;W[br];B[aq] (;W[er];B[dr] (;W[dq];B[es]) (;W[es];B[dq]) (;W[ao];B[bq] (;W[dq];B[es]) (;W[es];B[dq])) (;W[cr];B[es]) (;W[bq];B[ao] (;W[dq];B[es]) (;W[es];B[dq]) (;W[an];B[ap] (;W[dq];B[es]) (;W[es];B[dq]) (;W[cr];B[es])))) (;W[dr];B[er]) (;W[cr];B[dr]) (;W[bq];B[ao] (;W[dr];B[er]) (;W[er];B[dr] (;W[dq];B[es]) (;W[es];B[dq]) (;W[an];B[ap] (;W[dq];B[es]) (;W[es];B[dq]) (;W[cr];B[es]))) (;W[cr];B[dr]) (;W[ar];B[ap] (;W[dr];B[er]) (;W[er];B[dr] (;W[es];B[dq]) (;W[an];B[es]) (;W[cr];B[es]) (;W[dq];B[es])) (;W[cr];B[dr]) (;W[an];B[dr]))) (;W[ar];B[ao] (;W[dr];B[er]) (;W[er];B[dr]) (;W[cr];B[dr]) (;W[an];B[ap] (;W[dr];B[er]) (;W[cr];B[dr]) (;W[er];B[dr] (;W[dq];B[es]) (;W[es];B[dq]) (;W[cr];B[es]))) (;W[bq];B[ap] (;W[dr];B[er]) (;W[er];B[dr] (;W[es];B[dq]) (;W[an];B[es]) (;W[cr];B[es]) (;W[dq];B[es])) (;W[cr];B[dr]) (;W[an];B[dr])))) (;W[cr];B[br] (;W[er];B[dr] (;W[dq];B[cs] (;W[es];B[aq]) (;W[eq];B[es]) (;W[aq];B[es])) (;W[cs];B[es]) (;W[es];B[aq] (;W[dq];B[cs]) (;W[cs];B[bs]) (;W[ds];B[cs]))) (;W[dr];B[er] (;W[bq]) (;W[aq];B[ar] (;W[dq];B[bq]) (;W[ao];B[bq]) (;W[bs];B[dq])) (;W[ar];B[bs] (;W[dq];B[bq]) (;W[bq];B[aq]C[If Black cannot win the ko the connection at A is good enough. If White plays B instead of the ko then Black connects the ko; White A does not work..]LB[ao:B]LB[dq:A]) (;W[aq];B[bq])) (;W[bs] (;B[aq]) (;B[ar] (;W[dq];B[bq]) (;W[bq]) (;W[aq]))) (;W[dq];B[bq])) (;W[ar];B[bs];W[er] (;B[dq] (;W[dr];B[bq]) (;W[bq];B[aq];W[dr];B[ao];W[an];B[bq])) (;B[dr];W[dq];B[cs];W[es];B[eq]MA[aq]C[Black can also live in double ko by playing at A3.]))) (;W[aq];B[br] (;W[er];B[dq]) (;W[dr];B[er] (;W[bq]) (;W[ar];B[bs]) (;W[cr];B[ar]) (;W[dq];B[ar]) (;W[cs];B[ar]) (;W[ds];B[ar]) (;W[bs];B[ar])) (;W[cr];B[dr]) (;W[ar];B[bs] (;W[er];B[dq]) (;W[bq];B[dr]) (;W[dr];B[er])) (;W[bq];B[ar] (;W[er];B[dq] (;W[cr];B[ao]) (;W[ao];B[dr])) (;W[cr];B[ao]) (;W[dr];B[er]))) (;W[ar];B[br] (;W[dr];B[er] (;W[cr]) (;W[bs];B[cs]) (;W[bq]) (;W[dq];B[ds]) (;W[aq]) (;W[cs];B[bs]) (;W[ds];B[bs])) (;W[er];B[dr] (;W[dq];B[es]) (;W[es];B[dq]) (;W[bs];B[cs] (;W[es];B[dq]) (;W[dq];B[as] (;W[es];B[aq]) (;W[eq];B[aq]) (;W[aq];B[es]) (;W[ds];B[es] (;W[bs];B[eq]) (;W[aq];B[eq]))) (;W[aq];B[es]) (;W[bq];B[as]TR[ar]TR[bq]C[The marked stones are captured with double ko.])) (;W[aq];B[es])) (;W[cr];B[bs];W[er] (;B[dq] (;W[dr];B[bq]) (;W[bq];B[aq];W[dr];B[ao];W[an];B[bq])) (;B[dr];W[dq];B[cs];W[es];B[eq]MA[aq]C[Black can also live in double ko by playing at A3.])) (;W[bs];B[cs] (;W[er];B[dr] (;W[es];B[dq]) (;W[dq];B[as] (;W[es];B[aq]) (;W[eq];B[aq]) (;W[aq];B[es]) (;W[ds];B[es] (;W[bs];B[eq]) (;W[aq];B[eq]))) (;W[aq];B[es]) (;W[bq];B[as]TR[ar]TR[bq]C[The marked stones are captured with double ko.])) (;W[dr];B[er]) (;W[bq];B[aq]C[Black lives with double ko]) (;W[aq];B[dr])) (;W[bq];B[cr]) (;W[cs];B[bs] (;W[dr];B[er]) (;W[er];B[dq]) (;W[cr];B[dr]))) (;W[cs];B[aq];W[er];B[dr] (;W[es];B[dq] (;W[ds];B[br] (;W[cr];B[ao]) (;W[bs];B[ar] (;W[cr];B[ao]) (;W[ao];B[fs])) (;W[ar];B[ao] (;W[an];B[bs]) (;W[cr];B[bs]) (;W[bs];B[cr])) (;W[ao];B[bs])) (;W[br];B[ds]) (;W[ao];B[ds]) (;W[ar];B[ao] (;W[ds];B[bs] (;W[br];B[cr]) (;W[cr];B[br]) (;W[an];B[br])) (;W[br];B[ds]) (;W[an];B[ds]))) (;W[ao];B[es]) (;W[dq];B[es]) (;W[cr];B[es]) (;W[ds];B[es]) (;W[br];B[es])) (;W[ds];B[aq] (;W[er];B[dq]) (;W[dr];B[er]) (;W[br];B[dr]) (;W[cr];B[dr]) (;W[ar];B[ao];W[er];B[dq];W[cs];B[dr];W[es];B[bs] (;W[br];B[cr]) (;W[cr];B[br]) (;W[an];B[br]))) (;W[bs];B[aq];W[er];B[dq];W[ds];B[dr];W[es];B[fs];W[cs];B[br]) (;W[ao];B[aq] (;W[br];B[bq] (;W[er];B[dr] (;W[dq];B[es]) (;W[es];B[dq])) (;W[dr];B[er])) (;W[er];B[dr];W[dq];B[es]) (;W[dr];B[er]))) (;W[aq];B[dr]) (;W[ar];B[dr]) (;W[cs];B[dr]) (;W[bs];B[dr]) (;W[ds];B[dr]) (;W[es];B[dr]) (;W[ao];B[dr] (;W[ap];B[br]) (;W[aq];B[ap]) (;W[bq];B[ap]) (;W[cq];B[bq]) (;W[ar];B[ap]) (;W[br];B[ap]) (;W[cr];B[ap])) (;W[as];B[dr]))