(;AB[cd]AB[dd]AB[fc]AB[ic]AB[ib]AB[ee]AB[ef]AB[df]AB[eg]AB[eh]AB[ei]AW[fd]AW[de]AW[ce]AW[cf]AW[cg]AW[dg]AW[di]AW[dj]AW[fk]AW[gi]AW[ih]AW[if]AW[id]AW[jc]LB[fd:1]AB[gc]AW[ed]LB[gc:2]LB[ed:3]C[Black holds a small lead and most of the board is already settled. In a feat of desperation, white attaches at F16. Seeing black's calm reply at G17, white immediately cuts at E16 but it is an overplay.Black to play and punish white!]AW[lc]AP[goproblems]
(;B[ge];W[ec]
(;B[db];W[eb]
(;B[dc];W[fe]
(;B[gf];W[ff]
(;B[gg];W[fg];B[fh]C[White cannot save her 7 stones! Well done!RIGHT]TR[eb]TR[ec]TR[ed]TR[fd]TR[fe]TR[ff]TR[fg])
(;B[fg];W[gd];B[hd];W[he])
(;B[gh];W[fg]
(;B[gg];W[fh];B[fi];W[fj])
(;B[fh];W[gg];B[hg];W[hh];B[hf];W[fi])))
(;B[ff];W[gd]C[])
(;B[gg];W[gd]))
(;B[cb]C[Black needs to remove white's liberty while protecting the corner.]TR[dc]))
(;B[dc];W[db]C[Black's corner is too tight on liberties to fight effectively with white.];B[cb];W[bd];B[cc];W[fb]C[White pushes through with G16 or captures the corner next, and the overplay was successful.];B[da]
(;W[ea]C[White can make Ko like this too, but it's not as good as E18.])
(;W[eb]C[];B[bc];W[be]
(;B[gb];W[ba]C[The corner is captured.])
(;B[ba];W[ab]
(;B[gb];W[ac]C[The corner is captured.])
(;B[ac];W[ea]C[White gets a favourable Ko.CHOICE]))))
(;B[eb];W[db]))
(;B[gd]
(;W[ec]C[CHOICE]
(;B[fe];W[db]C[This position might as well as be a problem of its own. Please comment if I've missed anything!]
(;B[eb];W[dc]C[This exchange isn't helpful.])
(;B[dc];W[eb]C[Black's corner is too tight on liberties to fight on.])
(;B[cb];W[cc];B[bd];W[bb];B[dc];W[eb]
(;B[ca];W[bc])
(;B[bc];W[ca]C[White gets a favourable Ko.]))
(;B[cc];W[cb]C[];B[bb];W[fb]
(;B[be];W[gb]
(;B[ba];W[hc]
(;B[hd];W[hb];B[jb];W[jd]TR[ge]TR[kb])
(;B[hb];W[hd];B[ge];W[jb]))
(;B[hb];W[ge]
(;B[gf];W[he])
(;B[he];W[gf]
(;B[hd];W[ie])
(;B[ie];W[hd];B[hc];W[jd]))
(;B[hc];W[jb]))
(;B[hc];W[ba]))
(;B[ba];W[gb])
(;B[gb];W[ba]
(;B[bc];W[be];B[fa];W[eb];B[ca];W[da];B[ga];W[bd];B[ea];W[ab];B[ac];W[ad]C[Ko.])
(;B[ac];W[bd])
(;B[bd];W[ab]
(;B[ac]C[Ko.])
(;B[bc];W[be]))
(;B[ab];W[bd])))
(;B[bc];W[cc];B[bd];W[bb];B[dc];W[eb];B[cb];W[ca]C[White gets a favourable Ko.])
(;B[bb]
(;W[bd];B[cc];W[bc];B[cb]C[];W[fb]
(;B[ab];W[gb]
(;B[hb];W[ge])
(;B[hc];W[ca];B[ea];W[eb];B[da];W[ba];B[aa];W[ca];B[ba];W[be];B[hb];W[fa]
(;B[ca];W[ac])
(;B[ha];W[ca];B[da])))
(;B[be];W[gb]
(;B[bf];W[hc]
(;B[hd];W[hb];B[jb];W[jd]TR[ge]TR[kb])
(;B[hb];W[hd];B[ge];W[jb]))
(;B[ad];W[hc])
(;B[ac];W[hc])
(;B[hb];W[ge]
(;B[hc];W[jb];B[he];W[gf];B[hf];W[gg];B[hd];W[ie])
(;B[he];W[gf];B[hd];W[ie])
(;B[jb];W[he];B[hc]))
(;B[hc];W[bf]))
(;B[gb];W[ab];B[fa]C[White gives up some stones but reduces the corner in sente.]))
(;W[fb];B[gb]
(;W[bc])
(;W[cc];B[bd];W[bc];B[dc];W[cb];B[eb];W[ba]))
(;W[cc];B[bd];W[bc]
(;B[ac];W[dc])
(;B[dc];W[cb];B[eb];W[ad]
(;B[ae];W[ac])
(;B[ab];W[be]))))
(;B[bd];W[bb];B[cb];W[cc];B[dc];W[eb]
(;B[ca];W[bc])
(;B[bc];W[ca]C[White gets a favourable Ko.])))
(;B[db];W[eb];B[dc];W[fe]
(;B[ge];W[ff]
(;B[gg];W[gf];B[hf];W[hg])
(;B[gf];W[fg]
(;B[gh];W[gg];B[hg];W[hh])
(;B[gg];W[fh])))
(;B[gf];W[ge];B[he];W[hf];B[hd];W[ff];B[gg];W[fg])
(;B[gg];W[ge];B[he];W[hf]))
(;B[eb];W[dc]C[];B[cc];W[fe]C[See variation from blackG16 - whiteF15 for continuations.]))
(;W[fe]C[This is a much simpler refutation compared to white playing at E17]
(;B[ge];W[ff]
(;B[gg];W[gf];B[hf];W[hg])
(;B[gf];W[fg]
(;B[gg];W[fh])
(;B[gh]
(;W[gg];B[hg];W[fh])
(;W[fh];B[fi];W[gg]))))
(;B[gf];W[ec]
(;B[eb];W[db])
(;B[db];W[eb];B[dc];W[ge];B[he];W[hf];B[hd];W[ff];B[gg];W[fg]))))
(;B[he];W[ec];B[db];W[eb];B[dc];W[ge]
(;B[hd];W[gf];B[hf];W[gg]C[White's stones at the top are hurt, but black needs another move to protect the corner and gives up 6 stones himself.])
(;B[gf];W[hd];B[gd];W[fe]
(;B[ff];W[hf])
(;B[hf];W[hc]TR[fc]TR[gc]TR[gd]C[Black's stones are captured.])))
(;B[fe];W[gd])
(;B[ec];W[gd])
(;B[gf];W[gd])
(;B[hd];W[ge]))