(;GM[1]FF[4]CA[UTF-8]AP[CGoban:2]ST[2] RU[Japanese]SZ[19]KM[0.00]TM[] PW[Weiß]PB[Schwarz]AW[qa][ac][cc][ec][fc][qc][dd][pd][qe][qf][cn][bo][do][go][io][jo][bp][pp][bq][nq][oq][qq][sq][cr][er][cs][ds]AB[gm][dn][en][hn][ho][cp][dp][cq][eq][ar][br][dr][bs]TR[cr][er][cs][ds]C[White to play and save the marked stones!]PL[W] ;W[dq]CR[dq] ;B[es]LB[aq:A]CR[es]C[Black has to prevent a white move at A] ;W[fs]CR[fs] ;B[dr]CR[dr] ;W[es]CR[es] ;B[fr]CR[fr]C[So black has no choice.....] (;W[gs]CR[gs] ;B[gr]CR[gr] ;W[hs]CR[hs] ;B[hr]CR[hr] ;W[is]CR[is] ;B[ir]CR[ir] ;W[js]CR[js] ;B[jr]CR[jr] ;W[ks]CR[ks] ;B[kr]CR[kr] ;W[ls]CR[ls] ;B[lr]CR[lr] ;W[ms]CR[ms] ;B[mr]CR[mr] ;W[ns]CR[ns] ;B[nr]CR[nr] ;W[os]CR[os] ;B[or]CR[or] ;W[ps]CR[ps] ;B[pr]CR[pr] ;W[qs]CR[qs] ;B[qr]CR[qr] ;W[rs]CR[rs] ;B[rr]CR[rr]C[U] ;W[dq]CR[dq] ;B[ss]CR[ss]C[Finally, white got a chance to take the ko, but black gives one more atari...] ;W[sr]CR[sr] ;B[dr]CR[dr]C[.. and retakes the ko. ] ;W[ss]CR[ss] ;B[rq]CR[rq] ;W[sp]CR[sp] ;B[rp]CR[rp] ;W[so]CR[so] ;B[ro]CR[ro] ;W[sn]CR[sn] ;B[rn]CR[rn] ;W[sm]CR[sm] ;B[rm]CR[rm] ;W[sl]CR[sl] ;B[rl]CR[rl] ;W[sk]CR[sk] ;B[rk]CR[rk] ;W[sj]CR[sj] ;B[rj]CR[rj] ;W[si]CR[si] ;B[ri]CR[ri] ;W[sh]CR[sh] ;B[rh]CR[rh] ;W[sg]CR[sg] ;B[rg]CR[rg] ;W[sf]CR[sf] ;B[rf]CR[rf] ;W[se]CR[se] ;B[re]CR[re] ;W[sd]CR[sd] ;B[rd]CR[rd] ;W[sc]CR[sc] ;B[rc]CR[rc] ;W[sb]CR[sb] ;B[rb]CR[rb] ;W[dq]CR[dq] ;B[sa]CR[sa]C[You already know this :)] ;W[ra]CR[ra] ;B[dr]CR[dr] ;W[sa]CR[sa] ;B[qb]CR[qb] ;W[pa]CR[pa] ;B[pb]CR[pb] ;W[oa]CR[oa] ;B[ob]CR[ob] ;W[na]CR[na] ;B[nb]CR[nb] ;W[ma]CR[ma] ;B[mb]CR[mb] ;W[la]CR[la] ;B[lb]CR[lb] ;W[ka]CR[ka] ;B[kb]CR[kb] ;W[ja]CR[ja] ;B[jb]CR[jb] ;W[ia]CR[ia] ;B[ib]CR[ib] ;W[ha]CR[ha] ;B[hb]CR[hb] ;W[ga]CR[ga] ;B[gb]CR[gb] ;W[fa]CR[fa] ;B[fb]CR[fb] ;W[ea]CR[ea] ;B[eb]CR[eb] ;W[da]CR[da] ;B[db]CR[db] ;W[ca]CR[ca] ;B[cb]CR[cb] ;W[ba]CR[ba] ;B[bb]CR[bb] ;W[dq]CR[dq] ;B[aa]CR[aa] ;W[ab]CR[ab] ;B[dr]CR[dr] ;W[aa]CR[aa] ;B[bc]CR[bc] ;W[ad]CR[ad] ;B[bd]CR[bd] ;W[ae]CR[ae] ;B[be]CR[be] ;W[af]CR[af] ;B[bf]CR[bf] ;W[ag]CR[ag] ;B[bg]CR[bg] ;W[ah]CR[ah] ;B[bh]CR[bh] ;W[ai]CR[ai] ;B[bi]CR[bi] ;W[aj]CR[aj] ;B[bj]CR[bj] ;W[ak]CR[ak] ;B[bk]CR[bk] ;W[al]CR[al] ;B[bl]CR[bl] ;W[am]CR[am] ;B[bm]CR[bm] ;W[an]CR[an] ;B[bn]CR[bn] ;W[ao]CR[ao] ;B[aq]LB[ap:B][as:A]CR[aq]C[Black plays this way in order to prevent a second eye. Now, if black can play A, white will be dead even if he captures the five black stones. Therefore he must gain a liberty and then play B. ] (;W[ep]CR[ep] (;B[fp]CR[fp] ;W[eo]CR[eo] (;B[dq]CR[dq] ;W[co]CR[co] ;B[fq]CR[fq] ;W[ap]CR[ap] ;B[fo]LB[as:A]CR[fo]C[White wants to capture at A, but before that he needs at least a ko threat or two liberties. Black prevents this as long as possible!] ;W[cm]CR[cm] ;B[dm]CR[dm]C[From now on it's plain sailing again.] ;W[cl]CR[cl] ;B[dl]CR[dl] ;W[ck]CR[ck] ;B[dk]CR[dk] ;W[cj]CR[cj] ;B[dj]CR[dj] ;W[ci]CR[ci] ;B[di]CR[di] ;W[ch]CR[ch] ;B[dh]CR[dh] ;W[cg]CR[cg] ;B[dg]CR[dg] ;W[cf]CR[cf] ;B[df]CR[df] ;W[ce]CR[ce] ;B[de]CR[de] ;W[cd]CR[cd] ;B[ed]CR[ed] ;W[dc]CR[dc] ;B[fd]CR[fd] ;W[gc]CR[gc] ;B[gd]CR[gd] ;W[hc]CR[hc] ;B[hd]CR[hd] ;W[ic]CR[ic] ;B[id]CR[id] ;W[jc]CR[jc] ;B[jd]CR[jd] ;W[kc]CR[kc] ;B[kd]CR[kd] ;W[lc]CR[lc] ;B[ld]CR[ld] ;W[mc]CR[mc] ;B[md]CR[md] ;W[nc]CR[nc] ;B[nd]CR[nd] ;W[oc]CR[oc] ;B[od]CR[od] ;W[pc]CR[pc] ;B[pe]CR[pe] ;W[qd]CR[qd] ;B[pf]CR[pf] ;W[qg]CR[qg] ;B[pg]CR[pg] ;W[qh]CR[qh] ;B[ph]CR[ph] ;W[qi]CR[qi] ;B[pi]CR[pi] ;W[qj]CR[qj] ;B[pj]CR[pj] ;W[qk]CR[qk] ;B[pk]CR[pk] ;W[ql]CR[ql] ;B[pl]CR[pl] ;W[qm]CR[qm] ;B[pm]CR[pm] ;W[qn]CR[qn] ;B[pn]CR[pn] ;W[qo]CR[qo] ;B[po]CR[po] ;W[qp]CR[qp] ;B[op]CR[op] ;W[pq]CR[pq] ;B[np]CR[np] ;W[mq]CR[mq] ;B[mp]CR[mp] ;W[lq]CR[lq] ;B[lp]CR[lp] ;W[kq]CR[kq] ;B[kp]CR[kp] ;W[jq]CR[jq] ;B[jp]CR[jp] ;W[iq]CR[iq] ;B[ip]CR[ip] ;W[hq]CR[hq] ;B[hp]CR[hp] ;W[as]CR[as] ;B[ar]CR[ar] ;W[br]CR[br] ;B[bs]LB[aq:A]CR[bs]C[Black successfully prevented white from getting two liberties (in which case white would be able to atari at A), but in the process white has gained a ko threat!] (;W[fn]CR[fn] ;B[gp]CR[gp] ;W[as]LB[aq:A]CR[as]C[Eventually, white will capture at A and live. RIGHT CHOICE]) (;W[gp]CR[gp] ;B[fn]CR[fn] ;W[as]LB[aq:A]CR[as]C[Eventually, white will capture at A and live. RIGHT])) (;B[fq]LB[dq:A]CR[fq]C[This is a mistake by black, A is the only move!] ;W[dq]CR[dq]C[White lives. RIGHT CHOICE])) (;B[eo]CR[eo] ;W[fp]CR[fp] ;B[co]CR[co] ;W[dq]CR[dq] ;B[do]CR[do] ;W[fq]TR[eo]CR[fq]C[ White is alive, but only because black made a mistake: he can't atari with the marked stone! RIGHT CHOICE])) (;W[dq]CR[dq] ;B[ep]CR[ep] (;W[ap]CR[ap] ;B[co]CR[co] ;W[as]CR[as] ;B[ar]CR[ar] ;W[br]CR[br] ;B[bs]LB[as:A]TR[dq]CR[bs]C[Since there is no ko threat, white is dead - black will connect at A with his next move. Taking the ko (the marked stone) was a mistake! ]) (;W[co]CR[co] ;B[as]CR[as]C[There is only one eye in the corner, and it's impossible to gain another in the center - white is dead. Taking the ko (the marked stone) was a mistake! ]))) (;W[dq]CR[dq] ;B[gs]CR[gs]C[Obviously, white can't take the ko. That is, for the moment!]))