Strange thing - I have seen many endgame problems where you have to invade and destroy the most points. But defense is as important part of the game as offense.
This position does not look very complicated. Can you find the most efficient endgame tesuji there?
(;AW[bc]AW[cc]AW[dc]AW[ec]AW[gc]AW[gb]AW[gd]AW[ed]AB[hb]AB[hc]AB[hd]AB[de]AB[dd]AB[cd]AB[bd]AW[ge]AW[gf]AW[ff]AW[ef]AB[df]AW[ee]AB[dg]AB[eg]AB[fg]AB[gg]AB[hg]AB[hf]AB[he]AB[bf]AB[ga]C[White to play the best endgame in the left corner. The rest of the board is not important.]AB[bg]AB[cf]AW[ce]AB[ld]AB[nc]AB[md]AB[oa]AB[pa]AB[oc]AB[kd]AW[qa]AW[qb]AW[pb]AB[ob]AW[pc]AW[pd]AW[od]AB[nd]AW[oe]AW[ne]AW[me]AW[le]AB[ke]AW[kf]AB[jf]AB[jg]AW[kg]AW[mg]AP[goproblems];W[fa];B[ha]
(;W[ab]
(;B[ad];W[ac]C[The best you could do!RIGHT])
(;B[fb]C[NOTTHIS];W[ea];B[eb];W[da];B[db];W[ca];B[cb];W[ba]C[Black has nothing here.RIGHT]))
(;W[bb];B[ac];W[ab];B[ad]C[One point worse than the solution.])
(;W[eb];B[ac];W[ab];B[ad]
(;W[bb]C[Two points worse than the solution.])
(;W[ba]C[Two points behind the solution.])
(;W[cb]C[Two points behind the solution.]))
(;W[fb];B[ac];W[ab];B[ad]
(;W[bb]C[Two points behind the solution.])
(;W[ba]C[Two points behind the solution.])
(;W[cb]C[Two points behind the solution.]))
(;W[ba];B[ac];W[ab];B[ad]C[One point behind the solution.])
(;W[cb];B[ac];W[ab];B[ad]C[One point behind the solution.])
(;W[fc];B[ac];W[ab];B[ad]
(;W[bb]C[You could do two points better.])
(;W[ba]C[Two points behind the solution.])
(;W[cb]C[Two points behind the solution.]))
(;W[ea];B[ac];W[ab];B[ad]
(;W[bb]C[Two points behind the solution.])
(;W[ba]C[Two points behind the solution.])
(;W[cb]C[Two points behind the solution.]))
(;W[da];B[ac];W[ab];B[ad]
(;W[bb]C[Two points behind the solution.])
(;W[cb]C[Two points behind the solution.])
(;W[ba]C[Two points behind the solution.]))
(;W[ca];B[ac];W[ab];B[ad]
(;W[bb]C[Two points behind the solution.])
(;W[ba]C[Two points behind the solution.])
(;W[cb]C[Two points behind the solution.]))
(;W[db];B[ac];W[ab];B[ad]
(;W[bb]C[Two points behind the solution.])
(;W[ba]C[Two points behind the solution.])
(;W[cb]C[Two points behind the solution.]))
(;W[ad];B[fb];W[eb];B[ea];W[da];B[ae];W[fa];B[ac]
(;W[ab];B[bb]C[Black makes double ko and white will lose something.])
(;W[fc];B[bb]C[White could do better.])
(;W[bb];B[ea]C[Even if white wins this ko this is worse than the solution.]))
(;W[ac];B[fb]C[Problem.]))