(;C[This happened in a game of mine. Black played the triangled stone. Punish his mistake and win the game on the right side without a ko. There are other big moves (for example n16), but white can win by a significant amount with one tesuji.]AB[sl]AB[sm]AB[sn]AB[rl]AB[ql]AB[pk]AB[pm]AB[om]AB[on]AB[nn]AB[no]AB[mo]AB[ln]AB[lm]AB[ll]AB[lk]AB[kk]AB[kj]AB[mj]AB[ji]AB[jh]AB[jg]AB[jf]AB[kf]AB[ke]AB[le]AB[kd]AB[lc]AB[kb]AB[jb]AB[ib]AB[ic]AB[nr]AB[nq]AB[np]AB[gn]AB[dp]AB[cp]AB[co]AB[bn]AB[an]AB[cm]AB[dm]AB[el]AB[ek]AB[gm]AB[in]AB[im]AB[ik]AB[hk]AB[ho]AB[hp]AB[gp]AB[hq]AB[ir]AB[jr]AB[jq]AB[kq]AB[kp]AB[qj]AB[si]AB[dj]AB[di]AB[ei]AB[fi]AB[dh]AB[ch]AB[bh]AB[bi]AB[ab]AB[bb]AB[bc]AB[bd]AB[cd]AB[ce]AB[dd]AB[dc]AB[eb]AB[fb]AB[mf]AB[ne]AB[of]AB[pf]AB[qf]AB[qg]AB[rf]AW[nf]AW[ng]AW[og]AW[ph]AW[qh]AW[oe]AW[pd]AW[pe]AW[qe]AW[re]AW[nc]AW[je]AW[jd]AW[id]AW[hd]AW[jc]AW[kc]AW[ac]AW[ad]AW[ae]AW[be]AW[bf]AW[cf]AW[de]AW[ee]AW[ed]AW[ec]AW[gc]AW[gb]AW[dg]AW[eh]AW[fh]AW[gh]AW[jj]AW[ij]AW[ig]AW[if]AW[hi]AB[ih]AW[hh]AW[jk]AW[jl]AW[kl]AW[km]AW[kn]AW[ko]AW[kr]AW[lr]AW[mq]AW[mp]AW[lp]AW[lo]AW[al]AW[am]AW[bm]AW[cl]AW[dl]AW[dk]AW[bk]AW[bj]AW[cj]AW[ci]AW[cq]AW[dq]AW[fq]AW[fp]AW[fo]AW[go]AW[fn]AW[qm]AW[pl]AW[rm]AW[rn]AW[ro]AW[so]AW[pn]AW[po]AW[qp]AW[pq]AW[lj]AW[ki]AW[lh]TR[si]AP[goproblems] (;W[rh];B[sh] (;W[sg];B[rg] (;W[pg];B[sf] (;W[se];B[sg] (;W[rj];B[sj] (;W[sk];B[rk];W[ri]C[RIGHT] (;B[sk];W[qk]C[RIGHT]) (;B[qk];W[sk]C[RIGHT])) (;W[ri];B[sk];W[qk];B[ol];W[rk];B[pl]) (;W[rk];B[sk] (;W[ri];B[qk]) (;W[qk];B[ri]))) (;W[ri];B[sj];W[rj];B[sk];W[qk];B[ol];W[rk];B[pl]) (;W[sj];B[ri] (;W[qi];B[rj]) (;W[rj];B[qi])) (;W[rk];B[rj] (;W[ri];B[sj]) (;W[sj];B[ri])) (;W[sk];B[ri])) (;W[rj];B[sj];W[sk];B[rk];W[ri];B[sg];W[se] (;B[sk];W[qk]C[RIGHT]) (;B[qk];W[sk]C[RIGHT]) (;B[ol];W[sk]C[RIGHT])) (;W[sj];B[ri] (;W[qi];B[rj]) (;W[rj];B[qi]) (;W[se];B[sg] (;W[qi];B[rj]) (;W[rj];B[qi]))) (;W[ri];B[sj] (;W[rj];B[sk];W[se];B[sg];W[qk];B[ol];W[rk];B[pl]) (;W[rk];B[rj]) (;W[se];B[sg] (;W[rk];B[rj]) (;W[rj];B[sk];W[qk];B[ol];W[rk];B[pl]))) (;W[rk];B[ri]) (;W[sk];B[ri])) (;W[sf];B[se] (;W[sf];B[sg] (;W[rj];B[ri] (;W[qi];B[rk]) (;W[sj];B[qi])) (;W[ri];B[rj];W[sd];B[sf];W[pg];B[sj]) (;W[sj];B[ri] (;W[qi];B[rj]) (;W[rj];B[qi])) (;W[rk];B[qk] (;W[ri];B[rj]) (;W[rj];B[ri];W[qi];B[sj] (;W[sd];B[sf];W[pg];B[sk]) (;W[pg];B[rd])))) (;W[sg];B[sf];W[rj];B[ri];W[qi];B[sj] (;W[sd];B[rk];W[pg];B[sg]) (;W[pg];B[rd]))) (;W[se];B[sf];W[pg];B[sg];W[rj];B[sj] (;W[sk];B[rk];W[ri]C[RIGHT] (;B[sk];W[qk]C[RIGHT]) (;B[qk];W[sk]C[RIGHT])) (;W[ri];B[sk];W[qk]) (;W[rk];B[sk] (;W[ri];B[qk]) (;W[qk];B[ri]))) (;W[rj];B[sj] (;W[sk];B[rk];W[ri];B[qk];W[sk]C[RIGHT]) (;W[pg];B[sf];W[se];B[sg];W[sk];B[rk];W[ri]C[RIGHT] (;B[sk];W[qk]C[RIGHT]) (;B[qk];W[sk]C[RIGHT])) (;W[ri];B[sk] (;W[qk];B[ol]) (;W[pg];B[sf];W[se];B[sg];W[qk];B[ol];W[rk];B[pl])))) (;W[rg];B[sg];W[sf];B[se];W[pg];B[sf] (;W[sd];B[ri]) (;W[ri];B[rj];W[sd];B[sj]) (;W[rj];B[ri] (;W[qi];B[sj];W[sd];B[rk]) (;W[sj];B[qi]))) (;W[sf];B[sg] (;W[pg];B[rg];W[rj] (;B[ri];W[qi];B[se]) (;B[sj] (;W[sk];B[rk];W[ri];B[se];W[sd];B[sk];W[sf];B[qk]C[Not quite a ko]) (;W[qk];B[rk];W[ri];B[se];W[sd];B[sk];W[sf];B[qk]C[Not quite a ko]) (;W[rk];B[sk] (;W[ri];B[qk]) (;W[qk];B[ri])))) (;W[rg];B[se];W[pg];B[sf];W[rj];B[ri]) (;W[se];B[rg];W[rj];B[ri] (;W[qi];B[sj];W[pg];B[rk]) (;W[sj];B[qi]))) (;W[ri];B[sj] (;W[rg];B[sg] (;W[pg];B[sf] (;W[rj];B[sk]) (;W[se];B[rj])) (;W[sf];B[se] (;W[sd];B[sf] (;W[rj];B[sk]) (;W[rk];B[rj]) (;W[pg];B[rj])) (;W[pg];B[sf] (;W[sd];B[rj]) (;W[rj];B[sk])) (;W[rj];B[sk])) (;W[rj];B[sk])) (;W[rj];B[sk]) (;W[sg];B[rg] (;W[pg];B[sf] (;W[rj];B[sk];W[se];B[sg];W[qk];B[ol];W[rk];B[pl]) (;W[rk];B[rj]) (;W[se];B[sg] (;W[rk];B[rj]) (;W[rj];B[sk];W[qk];B[ol];W[rk];B[pl]))) (;W[sf];B[se]) (;W[rj];B[sk] (;W[qk];B[ol]) (;W[pg];B[sf];W[se];B[sg])) (;W[sk];B[rj])) (;W[sf];B[sg] (;W[se];B[rg] (;W[rj];B[sk]) (;W[rk];B[rj])) (;W[rg];B[se] (;W[sd];B[sf] (;W[rj];B[sk]) (;W[rk];B[rj]) (;W[pg];B[rj])) (;W[pg];B[sf] (;W[sd]) (;W[rj];B[sk])) (;W[rj];B[sk]))) (;W[pg];B[sg] (;W[rg];B[sf] (;W[rj];B[sk]) (;W[se];B[rj])) (;W[sf];B[se] (;W[rg];B[sf] (;W[sd]) (;W[rj];B[sk])) (;W[sd];B[rj] (;W[rg];B[sf]) (;W[sf];B[rg])) (;W[rj];B[sk])) (;W[rj];B[sk])))) (;W[rg];B[rh] (;W[sf];B[sg];W[pg];B[se] (;W[ri];B[rj]) (;W[sd];B[qi])) (;W[sg];B[sf] (;W[se];B[sh]) (;W[pg];B[sh]))) (;W[sf];B[sg] (;W[rh];B[sh] (;W[rg];B[se];W[pg];B[sf];W[rj];B[ri] (;W[qi];B[sj];W[sd];B[rk]) (;W[sj];B[qi])) (;W[pg];B[rg];W[rj] (;B[ri];W[qi];B[se]) (;B[sj];W[rk];B[sk];W[ri];B[qk]))) (;W[sh];B[rh];W[pg];B[se] (;W[ri];B[rj]) (;W[sd];B[qi]))) (;W[sg];B[rh] (;W[sf];B[rg] (;W[ri];B[rj];W[qi];B[sh];W[pg];B[se];W[sd];B[sf]) (;W[qi];B[ri])) (;W[ri];B[rg] (;W[qi];B[rj];W[sh];B[sf];W[sg];B[sj];W[se];B[sh]) (;W[sj];B[qi];W[sh];B[rj] (;W[sf];B[si]C[Nope, you can do better than a ko.]) (;W[si];B[sf];W[se];B[sk])) (;W[rj];B[sj] (;W[rk];B[sk] (;W[qk];B[qi]) (;W[qi];B[qk])) (;W[sf];B[sh] (;W[sk];B[rk];W[pg];B[se]) (;W[rk];B[sk] (;W[qk];B[qi]) (;W[qi];B[qk])))) (;W[sf];B[sh];W[rj];B[sj];W[rk];B[sk] (;W[qk];B[qi]) (;W[qi];B[qk])))) (;W[sh];B[rh];W[ri];B[sg];W[sj];B[qi];W[sh]C[Ko. You can do better!]) (;W[ri];B[rh] (;W[sj];B[qi];W[sh];B[sg] (;W[rg]C[Ko. White can live unconditionally.]) (;W[rj] (;B[si]) (;B[rk] (;W[si];B[sk]) (;W[rg]C[Ko. You can do better!])))) (;W[qi];B[rj]) (;W[rj];B[qi] (;W[sj];B[rk] (;W[sh];B[sg] (;W[si];B[sk]) (;W[rg]C[Ko. You can do better!])) (;W[rg];B[sg]) (;W[sf];B[sk] (;W[pg];B[rg]) (;W[rg];B[sg];W[pg];B[rg]))) (;W[sf];B[rk] (;W[sh];B[rg];W[pg];B[sj];W[sg];B[se]) (;W[sg];B[rg];W[pg];B[sj];W[sh];B[se])))) (;W[em];B[bq] (;W[br];B[ap] (;W[bo];B[dn]C[This is small compared to the upper right.]) (;W[dn];B[bo];W[cn]C[Small, white still loses the game.])) (;W[dn];B[ap] (;W[bo];B[br]) (;W[cn];B[br]C[This is small]))) (;W[md];B[me];W[ld];B[mc];W[nd] (;B[mh]C[This is a good exchange for white, but there is another, simpler tesuji that wins the game for white.]) (;B[li];W[mh];B[kh])))