(;GM[1]FF[4]CA[UTF-8]AP[CGoban:3]ST[2]
RU[Japanese]SZ[19]KM[0.00]
AW[bo][cp][dp][ep][fp][gp][hp][aq][bq][hq][hr][jr]AB[lp][cq][dq][fq][gq][ar][br][dr][gr][as][bs][hs]KK[^Bestiary^Xuanxuan Qijing]
(;W[fs]
(;B[eq]
(;W[es]
;B[gs]
(;W[ds]
(;B[er]
(;W[cr]
(;B[cs]
;W[cr]
;B[br]
(;W[bs]C[Here appears the thematic two-step ko]
;B[cs]
;W[ar]
;B[as]
(;W[ir]C[This incredible move is not even solid enough to prevent Black from excaping]
;B[fr]
(;W[bs]
;B[is]C[Threat of a ko threat]
(;W[cr]
;B[js]
(;W[kr]
;B[br]
;W[es]
;B[as]
;W[ds]C[Intrinsic threat]
;B[fs]
;W[bs]
;B[ks]
;W[lr]
(;B[as]C[The classic continuation ; Black will end captured on the next corner I still show all the variations I studied, because I dont want this work to be lost :-)]
;W[ds]C[Last white threat]
;B[es]
;W[bs]
;B[ls]
;W[cr]
(;B[mr]C[This  (the classical variation) is perhaps not fast enough]
;W[ds]
;B[ms]
(;W[mq]
;B[nr]
(;W[oq]
(;B[or]
(;W[pq]C[White cannot block]
;B[pr]
;W[qq]
;B[qr]
;W[rr]
;B[qs]
;W[os]
(;B[nq]
;W[np]
;B[mp]
;W[lq]
;B[op]
;W[no]
;B[rq]C[Up to that point,  no other way to exploit the weaknesses]
;W[rp]
;B[sq]TW[br][as]C[Two-stones edge squeeze]
;W[sr]
;B[qp]
;W[sp]
;B[rq]
;W[sq]
;B[pp]
;W[rq]C[Now, Black has many possible moves, but none seem to work (I almost never show White failures)]
(;B[qn]
;W[rn]C[Here again , more possibilities that would appear at first sight]
(;B[on]
(;W[nn]C[White must first prevent the geta, while getting some counter-attack]
(;B[ro]C[Perhaps the hardest move to refute]
;W[so]
;B[rm]
;W[qo]
;B[po]
;W[qm]
;B[ro]
;W[sn]
(;B[nm]
;W[lo]
(;B[pm]
;W[ql]
;B[rl]
;W[rk]
;B[qk]
;W[pl]
;B[rj]
;W[qo]
;B[pn]
;W[sk]C[Last hard tesuji...]
;B[sj]
;W[rs]
;B[cs]
;W[br]
;B[sl]
;W[ns]
;B[sm]
;W[ds]
;B[ps]
;W[ns]
;B[cs]
;W[rk]C[Enabling this miraculous intrinsic threat]
;B[sk]
;W[ds])
(;B[rl]
;W[pm]
(;B[pn]
;W[om])
(;B[om]
;W[pn]))
(;B[ql]
;W[pm]
;B[rl]
;W[pn]))
(;B[rl]
;W[pm]
;B[om]
;W[pn]
;B[oo]
;W[qo]
;B[nm]
;W[lo])
(;B[ql]
;W[pm]
;B[om]
;W[pl]
;B[ol]
;W[pk]
;B[pn]
;W[rl]
;B[mm]
;W[lo]))
(;B[rm]
;W[ro]
(;B[qo]
(;W[rl]C[Only defense]
;B[qm]
;W[sn]
;B[rs]
;W[sm]
;B[qk]
;W[rk]
;B[qj]
;W[rj]
;B[ri]
;W[ps]
;B[cs]
;W[br]
;B[sj]
;W[ss]
;B[ql]
;W[ds]
;B[ns]
;W[ps]
;B[cs]
;W[sl]
;B[si]
;W[ds]C[Black has no more threat])
(;W[rs]C[This move fails]
;B[cs]
;W[br]
;B[sn]
;W[ns]
;B[sm]
;W[ds]
;B[ps]
;W[ns]
;B[cs]
;W[qm]
;B[so]C[Black is alive]))
(;B[qm]
;W[rs]
;B[cs]
;W[br]
;B[sn]
;W[ds]
;B[qo]
;W[ns]
;B[cs]
;W[sm]
;B[sl]
;W[ds]
;B[ps]
;W[ns]
;B[cs]
;W[om]
;B[sm]
;W[ds]C[Easy for White]))
(;B[om]
;W[qm]
(;B[mm]
;W[lo]C[No geta in this case])
(;B[ln]
;W[mm]C[White escapes easily])))
(;W[rm]
;B[mn]
;W[rs]
;B[cs]
;W[br]
;B[nn]
;W[ds]
;B[oo]))
(;B[rm]C[This move must not be played first : Black is lost in a (short) ladder]
;W[qo]
;B[po]
;W[pn]
;B[ro]
;W[oo]
;B[qo]
;W[qm]
;B[sn]
;W[so]
;B[rn]
;W[rl])
(;B[pm]C[This move is quite tricky]
;W[rm]C[Forced]
;B[mn]
(;W[on]C[Only solution]
(;B[om]
;W[qo]
;B[po]
;W[pn]
;B[ro]
;W[oo]
;B[qo]
;W[qm]C[Another miracle])
(;B[pn]
;W[om]
(;B[ol]
;W[nm]C[Impossible to block]
(;B[cs]
;W[br]
(;B[ll]
;W[nl])
(;B[mk]
;W[mm]
;B[lm]
;W[ll]
;B[ml]
;W[ln]
;B[km]
;W[kp]
;B[lo]
;W[kn]
;B[ko]
;W[jn]
;B[jo]
;W[mo]
;B[oo]
;W[nn]
;B[nl]
;W[mn]
;B[in]
;W[jm]))
(;B[ql]
;W[rl]
;B[ll]
;W[nl]
;B[nk]
;W[ok]
;B[pl]
;W[mk]
;B[rk]C[White has too many liberties]
;W[rs]
;B[cs]
;W[br]
;B[ro]
;W[so]
;B[qo]
;W[ps]
;B[sl]
;W[ds]
;B[ns]
;W[ps]
;B[cs]
;W[sn]
;B[sk]
;W[ds]))
(;B[pl]
;W[nl]
(;B[rl]
;W[rs]
;B[cs]
;W[br]
;B[ro]
;W[so]
;B[qo]
;W[ps]
;B[qm]
;W[ds]
;B[ns]
;W[ps]
;B[cs]
;W[sn]
;B[sl]
;W[ds])
(;B[cs]
;W[br]
;B[rs]
;W[rk]
;B[ro]
;W[so]
;B[qo]
;W[sn]
;B[qj]
;W[rj])))
(;B[qm]
;W[om]
;B[ol]
(;W[nm]
;B[rl]
;W[qo]
;B[po]
;W[ro]
;B[pn]
;W[rs]
;B[cs]
;W[br]
;B[ll]
;W[nl]
;B[nk]
;W[pl])
(;W[qo]
;B[po]
;W[ro]
;B[pn]
;W[nm]
;B[rl]
;W[rs]
;B[cs]
;W[br]
;B[ll]
;W[nl])))
(;W[nn]C[One liberty missing]
;B[cs]
;W[br]
;B[mm]
;W[nm]
;B[nl]
;W[rs]
;B[om]
;W[ps]
;B[on]
;W[ds]
;B[ns]
;W[ps]
;B[cs]
;W[qo]
;B[oo]))
(;B[qm]C[Another hard one]
;W[qo]
;B[po]
;W[ro]
(;B[on]
;W[nn]
;B[nm]
;W[lo]
;B[rm]
;W[rs]
;B[cs]
;W[br]
;B[sn]
;W[ps]
;B[sm]
;W[ds]
;B[ns]
;W[ps]
;B[cs]
;W[pn]
;B[pm]
;W[ds])
(;B[pn]
;W[rm]
;B[mn]
;W[nn]
;B[mm]
;W[nm]
;B[nl]
;W[om]
;B[ol]
;W[ql]
(;B[pl]
;W[pm]
;B[mo]
;W[rl])
(;B[pm]
;W[pl])))
(;B[ro]C[Against the hanekomi, but Black loses one liberty]
;W[so]
;B[qo]
(;W[qm]
(;B[rm]
;W[sn]
;B[rl]
;W[pn]
;B[pm]
;W[ql]
;B[pl]
;W[qk]
;B[on]
;W[oo])
(;B[on]
;W[nn]
(;B[rm]
;W[sn]
;B[ql]
;W[pm]
;B[om]
;W[rl]
;B[ln]
;W[mm]
;B[pl]
;W[sm]
;B[rk]
;W[rs]
;B[cs]
;W[br]
;B[pn]
;W[ps]
;B[sk]
;W[ds]
;B[ns]
;W[ps]
;B[cs]
;W[sl]
;B[rm]
;W[qm]
;B[pm]
;W[ds])
(;B[nm]
;W[lo]
;B[rm]
;W[sn]
;B[rl]
;W[ql]
;B[qk])))
(;W[rm]
;B[qm]
;W[ql]
;B[pl]
;W[qk]
;B[mn]
;W[nn]
;B[mm]
;W[nm]
;B[nl]
;W[om]
(;B[ol]
;W[pm]C[Temporary seki])
(;B[pm]
;W[ol]
;B[ok]
;W[nk]
;B[ml]
;W[pk]
;B[oj]
;W[oo]))))
(;B[ro]
;W[qo]
;B[po]
;W[qn]
;B[pn]
;W[rn]
;B[mn]
;W[nn]
;B[nm]
;W[mo]
;B[lo]
;W[ln]
;B[mm]
;W[ko])
(;B[pn]
;W[rn]
(;B[qn]
;W[rm]
;B[mn]
;W[nn]
;B[mm]
;W[om]
;B[ql]
(;W[rl]C[Failure, but I show it too, as it is quite tricky, alors je le montre aussi]
;B[ol]
;W[pm]
;B[qm]
;W[pl]
;B[pk]
(;W[qo]C[Even this clever order of moves...]
;B[po]
;W[ok]
(;B[rk]C[ ... fails]
;W[nl]
;B[ro]
;W[so]
;B[cs]
;W[br]
;B[rs]
;W[qo]
;B[sl]
;W[ss]
;B[ro])
(;B[nl]
;W[qk]
(;B[pj]
;W[on]
;B[ro]
;W[oo])
(;B[nm]
;W[pj])))
(;W[ok]C[Failure :]
;B[on]
;W[nm]
;B[nl]
;W[qk]
;B[pj]
;W[oo]
;B[mo]))
(;W[ol]
;B[rl]
;W[qo]
(;B[on]
;W[qm]
;B[po]
;W[pm]
;B[ro]
;W[oo])
(;B[po]
;W[ro]
(;B[rs]
;W[qm]
;B[pm]
;W[pl])
(;B[pl]
;W[rs]
;B[cs]
;W[br]
;B[ok]C[Too many white liberties]
;W[nl]
;B[mj]
;W[on]
;B[nk]
;W[ps]
;B[ml]
;W[ds]
;B[ns]
;W[cs]
;B[mo]
;W[qj]
;B[oo]
;W[os]))))
(;B[mn]
;W[nn]
;B[mm]
;W[nm]
;B[nl]
;W[pm]
;B[qn]
;W[qm]
;B[om]
;W[on]
;B[ol]
;W[qo]))
(;B[oo]
;W[on]
;B[nn]
;W[mo]
(;B[pn]
;W[om]
;B[nm]
;W[lo]
;B[ro]
;W[qo]
;B[po]
;W[qn]
;B[pm]
;W[rn])
(;B[qo]
;W[rn]
;B[nm]
;W[lo]
;B[pn]
;W[ro]))
(;B[qo]C[Strange, but even this move is hard to counter...]
;W[rn]
;B[qn]
;W[rm]
;B[qm]
;W[ql]
;B[pl]
;W[qk]
;B[mn]
;W[nn]
(;B[mm]
;W[nm]
;B[nl]
;W[om]
(;B[ol]
;W[pm]C[Another funny seki]
;B[oo]
;W[pn]
;B[mo]
;W[ro])
(;B[pm]
;W[ol]
;B[ok]
;W[pk]
;B[nk]
;W[oo]C[Seki or live]
(;B[mo]
;W[pn])
(;B[po]
;W[ro])
(;B[pn]
;W[ro]
;B[mo])))
(;B[nm]
;W[mo]
;B[lo]
;W[ln]
;B[mm]
;W[ko]))
(;B[on]C[Probably the worst move]
;W[oo]
(;B[pn]
;W[po]
;B[qo]
;W[qn])
(;B[qo]
;W[qn]
;B[ro]
;W[rn])))
(;B[cs]C[As it is absolute sente, Black must take the ko at the last possible moment ; I don't show it always in all the variations]
;W[br]
;B[nq]
;W[np]
;B[mp]C[Etc. (see main variation)]))
(;W[pr]
;B[nq]
;W[np]
;B[pq]
;W[op]
;B[qr]))
(;B[nq]C[This vaariation is almost as complicated]
;W[np]
;B[mp]
;W[lq]
;B[op]
;W[no]
(;B[pq]
;W[or]
;B[cs]
;W[pr]
;B[br]
;W[as]
;B[qq]
;W[qr]
;B[oo]
;W[nn]
;B[rr]
;W[rq]
;B[rp]
;W[pp]
;B[qp]
;W[po]
;B[on]
;W[qo]
(;B[nm]
;W[lo]
;B[ro]
;W[om]
;B[pn]
;W[qn]
;B[pm]
;W[rs]
;B[sq]
;W[cr]
;B[mn]
;W[mo]
;B[br]
;W[os]
;B[qs]
;W[cr]
;B[ko]
;W[kp]
;B[br]
;W[qm]
;B[pl]
;W[cr]
;B[ss]
;W[ds]C[Another example of how intricate it might become])
(;B[ro]
;W[om]
;B[pn]
;W[qn]
;B[pm]
;W[sr]
(;B[rs]
;W[rn]
(;B[qm]
;W[sp]
;B[sq]
;W[cr]
;B[so]
;W[ds]C[Another example of how intricate it might become])
(;B[sq]
(;W[os]
;B[pl]
;W[cr]
;B[nm]
;W[ds])
(;W[pl]C[Even there, one must be very careful]
;B[os]
;W[qm]
;B[qs]
;W[cr]
;B[ps]
;W[op]C[Black is already alive])))
(;B[sq]
;W[rs]
(;B[ss]
;W[cr]
;B[nm]
;W[ds])
(;B[os]
;W[rq]
;B[qm]
;W[sp]))))
(;B[or]C[Back to main variation])))
(;W[nq]C[Strange, but this move leaves more weaknesses]
;B[or]
;W[pq]
;B[pr]
;W[qq]
;B[qr]
;W[rr]
;B[qs]
;W[os]
;B[oq]
;W[op]
;B[np]
;W[mp]
;B[pp]
;W[no]
;B[qp]
;W[rq]
;B[rp]
;W[rs]
;B[sq]
;W[ns]
;B[cs]
;W[br]
;B[sr]))
(;AE[lp]C[In the original problem (without the marked stone), White might "simply" capture in geta]
;W[nq]
;B[mq]
;W[mp]
;B[lp]
(;W[np]
;B[or]
;W[nr]
;B[ns]
;W[pq]
;B[pr]
;W[qq]
;B[lq]
;W[lo]
;B[ko]
;W[kp]
;B[mo]
;W[ln]
;B[oq]
;W[op]
;B[qr]
;W[rq]
;B[rr]
;W[ro]
;B[sr]
;W[rs]
;B[os]
;W[qs])
(;W[mo]
;B[or]
;W[nr]
;B[oq]
;W[np]
;B[ns])))
(;B[nr]C[Black must come out as fast as possible ; this nex idea seems to work]
;W[ds]
;B[ms]
;W[mr]
;B[ns]C[even if black dont play the ko]
(;W[nq]C[Doesnt work; only the geta is left]
;B[or]
(;W[pq]
;B[pr]
;W[qq]
;B[qr]
;W[rq]
;B[rr]
;W[sr]
;B[rs]
;W[ps]
;B[oq]
;W[op]
;B[pp]
;W[oo]
;B[qo]
;W[ro]
;B[rp])
(;W[oq]
;B[pr]
;W[qq]
;B[qr]
;W[rq]
;B[rr]
;W[sr]
;B[rs]
;W[ps]
;B[pq]
;W[pp]
;B[qp]
;W[rp]
;B[qo]
;W[ro]
;B[qn]
;W[rn]
;B[qm]
(;W[cs]
;B[op]
;W[po]
;B[oo]
;W[pn]
;B[om])
(;W[op]
;B[rm]
;W[sq]
;B[sn]
;W[so]
;B[sm])))
(;W[oq]
;B[nq]
;W[op]
;B[np]C[even without the marked stone..])))
(;B[ls]C[Looks absurd, yet, this line, which seem to have been missed by almost everybody, let Black escapes.... if white follows suit ; but there is another possibility. I thought this ended the matter, but see move 36 of main variation]
(;W[mr]
;B[as]
;W[ds]
;B[es]
;W[bs]
;B[ms]
;W[cr]
;B[nr]
;W[ds]
;B[ns]
(;W[oq]C[Without the extra stone, this geta could perhaps work ;  I show one exemple]
;B[nq]
;W[op]
;B[np]
;W[no]
(;AE[lp]
;B[mo]
;W[nn]
;B[pr]
;W[or]
;B[os]
;W[qq]
;B[qr]
;W[rq]
;B[rr]
;W[qo]
;B[lp]
;W[ln]
;B[mn]
;W[mm]
;B[nm]
;W[lm]C[Here, Black is caught. But...])
(;B[mo]C[With the stone in place, of course, it doesn't work]))
(;W[nq]
;B[or]
(;W[pq]
;B[pr]
;W[qq]
;B[qr]
;W[rq]
;B[rr]
;W[sr]
;B[rs]
;W[ps]
;B[oq]
;W[op]
;B[np]
;W[mq]
;B[pp]
;W[oo]
;B[qo]
;W[ro]
;B[rp]
;W[sp]
;B[qp]
;W[sq]
;B[ss])
(;W[oq]
;B[pr]
;W[qq]
;B[qr]
;W[rq]
;B[rr]
;W[sr]
;B[rs]
;W[ps]
;B[pq]
;W[pp]
;B[qp]
;W[rp]
;B[qo]
;W[ro]
;B[qn]
;W[rn]
;B[op]
;W[po]
;B[oo]
;W[pn]
;B[on]
;W[pm]
;B[mq]
;W[np]
;B[mp]
;W[no]
;B[nn]
;W[mo]
;B[lo]
;W[mn]
;B[mm]C[This sequence would succeed even without the extra stone])))
(;W[cr]C[This is possible too]
;B[mr]
;W[mq]
;B[br]
;W[oq]
;B[as]
;W[ds]
;B[es]
;W[bs]
;B[nr]
;W[cr]
;B[or]
;W[ds]
;B[ms]
;W[pq]C[We are back to main variation])))
(;W[ds]
;B[kr]
;W[kq]
;B[lr]
;W[lq]
;B[mq]))
(;W[js]
;B[as]
;W[ds]
;B[es]
;W[bs]
;B[cr]))
(;W[es]
;B[bs]))
(;W[is]C[Black would go through a faster block like a ghost]
;B[fr]
;W[bs]
;B[ir]
(;W[cr]
;B[iq]
;W[jq]
;B[br]
;W[es]
;B[js]
;W[ks]
;B[as]
;W[ds]
;B[is]
;W[bs]
;B[jp]C[No way to block]
;W[ip]
;B[kr]
;W[kq]
;B[lq]
;W[lr]
;B[kp]
;W[kr]
;B[mr])
(;W[iq]
;B[as]C[White has no threat])))
(;W[cs]
;B[bs]))
(;B[is]
;W[cs]))
(;W[is]
;B[cr]))
(;B[cr]
;W[er]))
(;W[cr]
;B[ds]
;W[cs]
;B[br]))
(;W[gs]
;B[es]
;W[cs]
;B[cr])
(;W[ds]C[Wrong order of moves]
;B[es]
;W[er]
;B[fr]
(;W[es]
;B[gs]
;W[cr]
;B[cs])
(;W[cs]
;B[gs])
(;W[cr]
;B[cs]
;W[cr]
;B[es]C[White has no ko threats
])))
(;B[gs]C[This simple variation is the only one given in the old collections !]
(;W[cs]
(;B[ds]C[Black looks alive, but this is a variant of thieves play]
;W[eq]
;B[er]
;W[is]
;B[fr]
;W[cr])
(;B[cr]C[Here, Black is dead (nakade)]
;W[er]
;B[eq]
;W[ds]
;B[es]
;W[ds]
(;B[is]
;W[kr]
;B[np]
;W[es]
;B[pp]
;W[fr])
(;B[fr]
;W[es]
;B[cs]
;W[es])))
(;W[ds]
;B[er]
;W[cr]
;B[es]
;W[cs]
;B[br])
(;W[er]
;B[eq]
;W[ds]
;B[fr]))
(;B[fr]
(;W[cs]
;B[ds]
;W[eq]
;B[er]
;W[gs])
(;W[ds]
;B[er]
;W[es])))
(;B[]
(;W[cs]C[Other attacks fail]
(;B[cr]
(;W[er]
;B[eq]
;W[fs]
;B[ds]
;W[gs]
;B[es])
(;W[eq]
;B[er]
;W[fs]
;B[gs]))
(;B[ds]
;W[fs]
(;B[gs]
;W[eq]
;B[er]
;W[is]
;B[fr]
;W[cr])
(;B[fr]
;W[eq])))
(;W[er]
;B[eq]
(;W[ds]
;B[fr]
(;W[cr]
;B[es])
(;W[es]
;B[fs]))
(;W[fs]
;B[fr]
;W[ds]
;B[gs]))
(;W[es]
;B[ds])))
