(;GM[1]FF[4]CA[UTF-8]AP[CGoban:3]ST[2]RU[Japanese]SZ[19]KM[0.00]PW[Invasion]PB[Hoshi]AB[pp]LB[qm:B][pn:C][qn:A]C[The Secret Of Corner Invasion (Hoshi): last update: 17.01.15.](;B[qn]LB[pq:D][qq:A][or:C][pr:B]C[Black aim to take territory.B is the most common technique. In most cases isn't good for white to go at A directly but if he has a lot of ko threats he can.](;W[qq];B[pq]LB[qp:A][rp:B](;W[qp](;B[qo];W[pr];B[or]LB[lp:C][qr:B][rr:A]C[A is a ko, white can connect at B if he has a stone around C, so that black must connect.](;W[rr];B[ps];W[qs]C[Ko. Black can avoid the ko but white will live.];B[os];W[ro];B[rn];W[rp];B[qr];W[rs])(;W[qr]LB[lp:A];B[nq];W[ro];B[rn];W[rp]))(;B[qr]C[Black can hane if he doesn't want to fight for the ko.];W[rr];B[pr]LB[rn:A][qo:B][ro:C]C[A is the best move. B and C are bad.](;W[rn]C[Note that playing kosumi or nobi instead for white isn't good otherwise black will be thicker.];B[rm];W[ro];B[qm];W[rs]LB[oo:C][po:A][qo:B]C[Later white can cut with the sequence from A to C since B is gote for black.])(;W[qo];B[po];W[rn];B[rm];W[sn];B[qm]C[Black is thick and if white tenuki, black will make a ko.];W[](;B[sr]C[Tesuji.];W[rs];B[sp];W[rp];B[sm];W[ro];B[rq]C[Ko.])(;B[sp]C[This move doesn't work.];W[rp];B[sq];W[rq];B[sm];W[sr]LB[so:A][rs:B]C[A and B are miai, so white is alive.]))(;W[ro];B[rn];W[rs];B[qo]LB[po:A]C[This is a sente move so the weakness at A is less important.])))(;W[rp]LB[qj:A][rn:B]C[This move is good if white has a stone around A. Since B is sente for white, black must block.];B[ro];W[qp];B[qo];W[rr]C[White is alive.])(;W[pr];B[or];W[rr];B[ps];W[qs]C[Ko.]))(;W[pr]LB[oq:B][pq:A][nr:C](;B[pq];W[or];B[qr];W[rr]LB[qq:A][qs:B]C[A is correct and solid, B leaves a lot of aji.](;B[qq];W[lq]C[Joseki.])(;B[qs]LB[qj:B][rn:C][rp:A]C[Bad aji for black. A is sente. If white has a stone around B, white can play at C.];W[rn]LB[rm:A][ro:B](;B[rm];W[qo]LB[pn:B][ro:A](;B[ro];W[rp];B[sn];W[qq])(;B[pn];W[qq]))(;B[ro];W[rp];B[qp];W[so];B[qo];W[rq];B[qq];W[rm]LB[qj:A])))(;B[oq];W[or];B[nr];W[nq](;B[mq]C[Strong move.];W[np];B[lr];W[qp];B[qq]LB[pq:A][rq:B]C[If the ladder is good for white he can play at B otherwise, he can only play A.](;W[pq];B[rp];W[op];B[qo]C[Black is risky since he must attack because he hasn't gained a lot of territory. White has no eye.])(;W[rq]C[White can play here if he has a ladder breaker.](;B[rp];W[qo];B[ro])(;B[pq];W[qr](;B[rp];W[qo];B[rr];W[po];B[sq];W[op];B[rq];W[ro];B[qs];W[on]C[Black has a corner and white has a nice influence, this is good for white.])(;B[po];W[ro]C[White lives in the corner and black isn't thick, this is good for white.]))))(;B[mr];W[qp];B[qo];W[rp];B[rr]C[Good move.];W[qr];B[np];W[rs]C[Joseki.]))(;B[nr](;W[oq];B[qq]LB[op:B][nq:A](;W[nq];B[mq];W[mp];B[lq]C[White has no eye.])(;W[op];B[mp];W[on];B[pl]C[Black is still chasing white.]))(;W[qq];B[qp](;W[oq];B[pq];W[or];B[qr](;W[nq]LB[lq:A][mr:B]C[B is too heavy.](;B[lq]C[Good move.];W[mr];B[lr]C[White has only one eye and is heavy.])(;B[mr]))(;W[op];B[mp];W[on];B[pl]))(;W[rr]LB[rp:B][nq:A](;B[nq];W[rp];B[ro]C[Joseki. White can tenuki to make a ko or make a live.])(;B[rp];W[oq]C[White will be easy to settle.])))))(;W[or]LB[oq:A][pq:B][pr:C](;B[pq];W[lq]LB[pr:A][qr:B]C[Since white didn't make the A-B exchange, he can choose to jump directly at B later.])(;B[oq]LB[nr:B][pr:A]C[A is the only move, B gives a very strong shape to black.](;W[pr];B[nr];W[nq]LB[mq:A][mr:B];B[mq];W[np];B[lr])(;W[nr];B[pr]C[Black's too thick.]))(;B[pr]LB[oq:A][pq:B]C[B used to be played but not anymore because it gives to black too many points. But A also gives to black quite a big corner.](;W[oq];B[pq];W[kq]C[Black's corner is big.])(;W[pq]LB[oq:A][qq:B]C[B is bad.](;B[oq];W[qq];B[qr];W[op];B[nq];W[qp];B[po](;W[nr];B[rr];W[mq];B[np];W[mo];B[no];W[nn];B[mp];W[lp];B[oo]LB[lo:A][lq:B][lr:C]C[Ancien joseki, because black has too much points. White has to reinforce at A, B or C according to the situation.])(;W[rr];B[nr];W[qs];B[os];W[sq]LB[rn:A]C[The corner is too small and A is black sente.]))(;B[qq];W[oq];B[qr];W[op];B[po]C[Black's corner is reduced.]))))(;W[pq]LB[oq:B][qq:A](;B[qq];W[oq];B[qr];W[op];B[po]LB[kp:A][kq:B][lq:C]C[White can extend at A, B or C.])(;B[oq](;W[or](;B[op];W[pr];B[nr];W[qp];B[qo];W[rp]C[Black's influence isn't very thick but white isn't solid either.])(;B[pr];W[qq];B[qr];W[op];B[nq];W[qp];B[po];W[nr];B[rr];W[mq];B[np];W[mo];B[no];W[nn];B[mp];W[lp];B[oo]LB[lo:A][lq:B][lr:C]C[Ancien joseki. Black is better. White has to reinforce at A, B or C.])(;B[qq];W[pr]LB[op:B][nq:A](;B[nq];W[nr];B[mq];W[rq]LB[qp:B][qr:A]C[Black can play A to make territory.](;B[qr];W[qp];B[rp];W[qo];B[rr];W[po];B[op];W[ro];B[sq];W[oo]C[White gets influence.])(;B[qp];W[qr];B[rp];W[rr]C[Black has a strong influence.]))(;B[op];W[qr];B[rq];W[mq]C[White is comforable and black is solid.])))(;W[qp](;B[po];W[qr];B[or];W[ro]LB[rn:A][rq:B]C[If black is very thick outside can play B but in most cases black plays A.](;B[rn];W[rq]C[Black has a good influence in sente but this is playable for white.])(;B[rq]))(;B[qq];W[pr];B[or]LB[po:A][rq:B]C[B is the right move, A gives to black a too strong shape.](;W[po];B[op];W[qo];B[rq]C[Black's shape is too good.])(;W[rq];B[qr];W[po];B[ps];W[qo];B[pn];W[oo];B[on]C[Black is chasing white. Fighting style.])))))(;W[ql];B[](;W[or];B[pr];W[po]LB[oo:A][qo:B]C[Trick move.Counter-attacking at A is good, whereas B is passive.](;B[qo];W[pq]LB[oq:A][qq:B]C[If black wants influence he can play at A.](;B[qq];W[oq](;B[qr];W[op];B[qp];W[om]C[This is unacceptable for black.])(;B[op];W[qr];B[rr];W[ps];B[rq];W[np];B[oo]C[White is comfortable in sente.]))(;B[oq];W[qq];B[op];W[qr];B[nr];W[ps];B[mq]C[Black gets a good influence.]))(;B[oo];W[pq];B[qq];W[oq];B[qr](;W[op];B[qp];W[no];B[on]C[Black has a good shape, it's good for black.])(;W[qp];B[op];W[qo];B[pn];W[rn]C[Black's next move is critical. There's a tesuji.](;B[rm];W[rq];B[rr];W[on]LB[pm:B][no:A]C[A and B are miai.])(;B[so]C[Tesuji];W[rq](;B[rr])(;B[sp]C[Tesuji again.](;W[rr];B[rp])(;W[ro];B[rm]))))))(;W[nq];B[];W[rp]LB[rn:B][pq:A]C[A and B are miai for white.];B[qp]C[This is the proper answer.];W[ro];B[qm];W[qq];B[pq];W[qr](;B[pl];W[pr];B[qk]C[Black is very thick.])(;B[pr]C[Black cannot play here.];W[rl]LB[sn:A][rr:B]C[White can connect or live at B.])))(;W[]LB[oq:A]C[Tenuki.];B[oq]LB[qq:A]C[There's still aji in the corner.](;W[qq]LB[qp:A][or:B][pr:C]C[This move can be a probe.](;B[qp]LB[nq:B][or:A]C[B is a good move when black has a moyo that white wants to invade.](;W[or]LB[nr:A][pr:B]C[A is a strong move, but it only works if black is solid outside. B is ok.](;B[pr];W[nr]C[Equal result.])(;B[nr]LB[nq:B][pr:A](;W[pr](;B[rp];W[rq];B[os];W[ps];B[sq];W[sr];B[rs]LB[jq:C][nq:B][mr:A]C[White can cut at B if he's strong around C.](;W[mr];B[nq];W[ns]C[White might escape.])(;W[nq]))(;B[rq]LB[nq:A][pq:B]C[This is a wrong move. A is better for white since it leaves aji.](;W[nq];B[mr];W[pq];B[op];W[rr];B[rp];W[sr]C[White is alive.])(;W[pq];B[nq];W[rr];B[rp];W[sr])))(;W[nq];B[mq];W[pq];B[np];W[rp];B[ro]LB[rr:A][os:B]C[B doesn't work.](;W[rr]C[Ko, but black is very thick, so white can only play this way in very specific cases.])(;W[os];B[rr];W[rq];B[qs];W[qr];B[rs];W[sr];B[ns];W[pr];B[sp]))))(;W[nq];B[or];W[mo]))(;B[or]LB[qk:A][rn:B][ro:C]C[This move isn't possible if white has a stone around A, then white will play at C. Otherwise, white will choose B.](;W[ro];B[rn];W[qo];B[po];W[qp];B[rs];W[qr];B[qs];W[rr];B[pr];W[pn]LB[qk:A]C[If there's a white stone at A black won't get a good result.])(;W[rn](;B[rm];W[ro];B[qm];W[rr]C[White is alive easily.])(;B[ro];W[rm];B[qo];W[qj])))(;B[pr]LB[rn:B][nr:A];W[nr]LB[or:B][qr:A]C[B isn't good.](;B[]C[Tenuki.];W[or];B[qp];W[qr])(;B[qp];W[or];B[qr])(;B[or]LB[rn:A]C[The result is already good for white, moreover he can still play at A.];W[rn])(;B[qr])))(;W[ql];B[]C[Tenuki.];W[mq];B[]LB[jq:B][qq:A]C[Tenuki.](;W[qq]LB[qp:A][pr:B]C[Black A is defensive, B is very dangerous.](;B[qp]LB[rp:A][pr:B](;W[or](;B[pr];W[nr];B[qr]C[White gets some profit in sente.])(;B[nr];W[pr];B[nq];W[rp];B[ro];W[rr];B[sp];W[rq]C[White is alive.]))(;W[rp]LB[ro:A][qr:B]C[Agressive move.](;B[ro];W[pr]LB[rq:B][or:A]C[Black can only block if he can win the ko, otherwise he must play at B.](;B[or];W[rr];B[sp];W[sq]C[Ko.];B[];W[so]C[White will be solid so, not only white got the corner but he'll have a chance to attack black.])(;B[rq];W[rr];B[sp];W[or]C[Black is thick but white gained a lot of territory.]))(;B[qr];W[rr];B[pr];W[rn];B[rm];W[qo];B[po];W[ro];B[qm];W[rs];B[sn];W[so];B[sq];W[rq];B[sr]C[Locally white is dead, but black has a lot of weaknesses.];W[pn]C[Dangerous fight for black.]))(;W[pr];B[or];W[rp](;B[ro];W[rr])(;B[rr];W[rq];B[ro];W[sr];B[rs];W[os];B[ns]LB[sp:1][lq:B][mq:A][pq:3][mr:C][qr:2][ps:4]C[If the white stone A was at B, this hane wouldn't be good. Because the white stone wouldn't be damaged as much as it will be when it's placed at A. So instead of blocking here, black should play at C if the white stone A was at B. Then there would be a ko with 1-4.];W[ps];B[mr];W[sp];B[lq];W[]C[Tenuki.];B[so];W[qr];B[pq]C[Seki.])))(;B[pr];W[ro];B[rn];W[qr]LB[qo:B][rp:A](;B[rp];W[qp];B[qo];W[rq];B[so];W[pq];B[or];W[op];B[po];W[nq];B[sq];W[rs];B[sr];W[nr]C[Black is dead.])(;B[qo];W[rp];B[so];W[sp];B[qs];W[rs];B[sr]C[White is dead locally but black has many weaknesses.];W[pq];B[or];W[op])))(;W[jq];B[]C[Tenuki.];W[ol];B[]LB[rp:B][qq:A]C[Tenuki.](;W[qq];B[qp];W[or];B[pr];W[nr];B[qr]C[Black is comfortable.])(;W[rp]LB[ro:B][qp:A]C[A is the proper move.](;B[ro];W[pr];B[or];W[qp](;B[po];W[rr]C[Black's shape isn't solid.])(;B[qo];W[pq]C[Black must answer.]))(;B[qp];W[ro];B[rq];W[rn];B[nr]C[Black still have the corner and white got profit in sente. It's acceptable for both side.]))))(;W[jq];B[];W[qi](;B[]LB[ql:B][mq:A][qq:C]C[When white cannot choose what is the best extension, it's good to play at C to decide.];W[qq]C[Probe.](;B[qp]LB[mq:A]C[In this case, A is good.];W[mq]LB[or:A]C[Then white will have A to get some extra profit.])(;B[or]LB[ql:A];W[ql]LB[ro:A]C[This extension is good since white will have A.]))(;B[lq];W[qq];B[qp]C[This is the right move.])(;B[qk];W[qq];B[pr]C[This is the right move to kill white.])))(;W[nq];B[pr]C[The value of this move is about 25 points and there's no aji in the corner. The shape is very strong.](;AW[ol][ql][nm][no][nr]C[Even like this black's corner is safe.])(;AW[ol][ql][nm][np];W[or]LB[on:C][oq:B][qq:A]C[Black must reinforce with A or B. In most cases it's better for black to reinforce with B. C is a mistake.](;B[qq])(;B[oq];W[nr];B[on]C[White cannot invade the corner because of this move.];W[qr];B[ps];W[qq];B[pq](;W[ro];B[rn];W[qo];B[po]LB[on:A]C[A protects the cutting point.];W[qp](;B[sp]C[Tesuji.];W[so];B[qs];W[rs];B[rr];W[sr];B[rq]C[White is dead.])(;B[qs]C[This move is a mistake.];W[rs];B[rr];W[rq];B[sr];W[sn];B[rm];W[sq]))(;W[qp];B[qo];W[ro];B[rn];W[so];B[rs];W[qs];B[rp];W[rq];B[sq]C[Tesuji.];W[sp];B[sr]C[White is dead.]))(;B[on];W[qr];B[ps];W[rp](;B[qq];W[rn])(;B[qp];W[ro];B[rn];W[qq];B[pq];W[sr]C[White is alive.])))))(;B[qm]LB[qq:A]C[This move is faster than the keima but the corner is more open.White can invade at A easily.](;W[qq]LB[qp:B][pq:A](;B[pq];W[qp]LB[po:B][qo:A][qr:C](;B[qo];W[ro];B[rn];W[po];B[qn];W[pr];B[or]LB[qr:A][rr:B]C[B is possible when white has more ko threats.](;W[qr];B[nq];W[rp]LB[oo:A]C[Black can tenuki is there's other urgent points.];B[oo]C[Joseki. Black is very thick but white had the corner in sente.])(;W[rr](;B[ps];W[qs])(;B[nq]LB[oo:A]C[White has sente so he can tenuki so black cannot choose whether to capture at A or tenuki.])))(;B[po](;W[ro]LB[rn:A]C[Black can tenuki.](;B[rn];W[qo];B[qn];W[pr];B[or];W[qr];B[nq]C[White has a slightly better corner compared to the classical joseki.])(;B[];W[qn];B[pn];W[pm];B[ql];W[om];B[qr];W[rr];B[rq]C[Tesuji.];W[rp];B[rn];W[qo];B[rs];W[sq];B[or];W[rm];B[rl];W[sn]C[Black has the sente and he's strong.]))(;W[qo]LB[pi:C][qn:B][qr:A]C[Black B if white has a group in the C area.](;B[qr];W[rr];B[pr];W[qn];B[pn]LB[pm:A][rm:B]C[White A is an overplay.](;W[pm];B[pl];W[om];B[ol];W[nm];B[rl]LB[rm:C][rn:B][rs:A]C[Good move. A can make white live by ko, B as well but is worse. Atari at C is the only way to live.](;W[rs];B[rn];W[ro];B[sp];W[sn];B[sm]C[Ko.])(;W[rn];B[rs];W[sr];B[rp];W[sp];B[so];W[rq]C[Black can also kill white by ko.])(;W[rm];B[ql]C[This exchange is very good for black tho.](;W[rs];B[rn]C[Black can capture in sente, black is very strong.];W[ro];B[sm])(;W[sm];B[sl]C[This move is sente, black is very strong.])))(;W[rm]LB[pg:D][ql:B][rl:C][jp:A]C[If black has a stone around A, he can nobi at B or hane at C to keep sente but he cannot choose this move if white has a group in the D area.](;B[ql];W[rl];B[qk]LB[jp:A]C[Black has a good influence.])(;B[rl];W[ql];B[pm];W[rk];B[pl];W[qk]LB[rn:A]C[Black is sente. Later A is a good move.];B[rn];W[sl];B[rq];W[rp];B[sr];W[sq];B[rs];W[];B[rq];W[];B[sp])))(;B[qn];W[pr];B[or];W[qr];B[nq]LB[sm:C][rn:A][sn:B]C[A-C are sente.])))(;B[qr]LB[qn:A][qo:C][rr:B]C[A is the right move, C is also possible. B is a mistake.](;W[qn];B[pn];W[po];B[oo];W[qo](;B[pm];W[rr];B[pr];W[rm];B[rl];W[sn];B[nn]C[Joseki. White is sente.])(;B[rm]C[An overplay.]))(;W[rr];B[pr](;W[qn];B[pn];W[po];B[oo];W[qo];B[rm]LB[pr:2][rr:1]C[Severe move. If 1-2 weren't exchanged black couldn't extend here.])(;W[qo];B[on];W[rs]C[White is gote and black is favorable.]))(;W[qo];B[po];W[rr];B[pr];W[qn];B[pn])))(;B[qp];W[pq];B[oq];W[or]LB[qm:C][nq:B][nr:A]C[B is bad since it makes the C stone inefficient.];B[nr](;W[nq];B[op];W[mr];B[pr];W[ns];B[qr]LB[qm:A]C[Black keeps the corner and white is sente. A isn't very well placed though.])(;W[pr];B[nq];W[rp];B[ro];W[rq]C[White can live but the corner is small.])))(;W[nq](;B[](;W[qk](;B[](;W[qq];B[pq];W[qp];B[po];W[pr];B[or];W[qr];B[oq];W[qo];B[qn];W[no];B[nn]C[A very important move.];W[mo];B[on]LB[rn:A][sn:B]C[A and B are sente.])(;W[pq];B[qq];W[qp]LB[po:A][qo:B]C[A is joseki.](;B[po];W[qr];B[rq]LB[or:A][pr:B]C[A leads to the joseki. B is a ticky play.](;W[or];B[rr];W[rs];B[qo]C[Joseki.])(;W[pr]LB[rp:A][rr:B]C[A is the correct move, B is a mistake.](;B[rr];W[rn]C[Tesuji.](;B[rm];W[rp]LB[qo:A][ro:B]C[A doesn't work and B makes a ko.](;B[qo];W[ro];B[rs];W[qs];B[sp];W[sr])(;B[ro];W[qo];B[qn];W[so];B[sr];W[rs];B[sp];W[sq]C[Bad for black.]))(;B[qn];W[ro];B[rp];W[rm];B[qo]C[White gets territory, it's bad for black.])(;B[qo];W[ro];B[rp];W[rm]C[It's also bad for black.])(;B[ro];W[qn];B[qo];W[pn]))(;B[rp])))(;B[qo];W[rp];B[oq];W[pr];B[op];W[or];B[rq];W[ro];B[rn];W[po]LB[qn:C][oo:A][sp:B]C[B captures white if the ladder if favorable. C is a mistake.](;B[sp];W[qn];B[so];W[qo];B[oo]C[Ladder.])(;B[oo];W[qn];B[pn];W[rr];B[qo];W[qr]C[White gets the corner in gote and black is very thick. Equal result.])(;B[qn];W[no];B[oo];W[on];B[pn];W[np];B[po];W[rr];B[so];W[qr];B[sp]C[Black's shape is horrible.]))))(;B[pq];W[nn];B[om]C[Honte move.];W[qn]LB[pm:C][pn:A][oo:B]C[Famous tricky play.A is the worst move, B is better but the right answer is C.](;B[pn];W[qo](;B[po];W[rm];B[pm];W[ql]C[White took away the territory.])(;B[rm]C[This is an overplay.]))(;B[oo](;W[no];B[rm])(;W[rm];B[mp]))(;B[pm]C[Right answer.];W[rm];B[rl];W[ro];B[sm];W[rn];B[ql];W[rq];B[oo];W[qr];B[pr];W[qp];B[mp]C[White is alive but he's splitted outside, so black is successful.])))(;W[no];B[]LB[qp:A](;W[qp]LB[po:A][qo:B]C[A is the right move.](;B[qo];W[po]LB[pn:B][pq:A][qq:C]C[B is a mistake.](;B[pn]LB[oo:B][pq:A]C[A is the proper move. B is a mistake, it gives to white the corner and black gets a bad shape.](;W[oo];B[qq];W[rp])(;W[pq];B[oo];W[op];B[po];W[rp]C[Black's shape is bad and white gets the corner.]))(;B[pq];W[qq];B[qr];W[rr](;B[pr];W[ro];B[qn];W[op];B[rs];W[sr](;B[nr];W[mr];B[ns];W[lq];B[rn];W[oq];B[or];W[qs];B[ps];W[rp];B[on];W[oo]C[Seki.];B[]C[Tenuki.];W[sn];B[sm];W[sp]C[Ko. Bad for black.])(;B[rn]C[This move doesn't work.];W[rq];B[sp];W[or]C[Black is dead.]))(;B[oo];W[pn];B[on];W[pm];B[om];W[pl]C[White will have a very large territory.]))(;B[qq];W[rp];B[pq];W[qn];B[pn];W[ro];B[oo]C[If white plays the ko this is huge.];W[qo];B[on];W[rm];B[np];W[mp];B[op];W[ql];B[mq];W[lq];B[mr];W[lp];B[lr];W[kr];B[nr]C[Good for black since he's a alive and white's shape is bad.]))(;B[po];W[pq];B[qq];W[qo];B[oq];W[pr];B[or];W[pn];B[op];W[qn];B[qr]C[This is the right way to play.]))(;W[po];B[qo];W[qp]))(;W[qp];B[pq];W[qn];B[pn];W[po];B[oo];W[qo]LB[np:A][qq:B]C[A gives to white a lot of territory.](;B[np];W[qq];B[qr];W[rr];B[pr];W[pm];B[on];W[ql]C[White gets a lot of territory.])(;B[qq]LB[rm:B][op:A](;W[op];B[pm];W[rm];B[rl];W[sn];B[qk];W[rq];B[rr];W[sq];B[nr];W[mr];B[or];W[no];B[on];W[sr];B[qr];W[ro];B[mq])(;W[rm];B[pm];W[rl];B[rp];W[ro];B[so];W[rn];B[rr]LB[qj:B][op:A]C[White A is an overplay.](;W[op];B[no]LB[qk:B][mq:A]C[A and B are miai for black.])(;W[qj];B[np]C[Good for black.])))))(;B[pq];W[qk];B[](;W[qn]LB[pn:A];B[pn];W[rm]LB[rn:B][qo:A](;B[qo];W[rn];B[pm];W[ro];B[rp];W[oo];B[po]C[Equal result.])(;B[rn];W[qo];B[ro];W[pm];B[ql]LB[rl:B][qp:A]C[B is not possible.](;W[qp]LB[rl:B][rp:A]C[B is not possible.](;B[rp];W[qq](;B[po];W[rl];B[pl];W[qr];B[pr];W[rq];B[om]C[Good for white. He gets a lot of territory with the corner in sente.])(;B[qr];W[rq];B[rr];W[po];B[sq];W[oo];B[rl];W[pl]C[White gets influence, it's good for white.]))(;B[rl]C[Black cannot play this way];W[po]))(;W[rl];B[pl];W[qp];B[rp];W[qq];B[qr];W[rq];B[rr];W[po];B[oo];W[on];B[sq];W[pn]C[A ladder appears.];B[nn])))(;W[qo]LB[po:A];B[po]LB[qn:A][ro:B](;W[qn]LB[pm:B][pn:A](;B[pn];W[rm];B[pm];W[ro]LB[rp:A];B[rp]C[Joseki.])(;B[pm]LB[pn:A][qr:B](;W[pn];B[on];W[rm];B[rl];W[rn];B[ql]LB[om:B][rq:A]C[B is an overplay even if black have to be careful.](;W[rq](;B[qr];W[rr];B[rs];W[om]C[White's group has a lot of liberties.])(;B[om]LB[qr:B][rr:A]C[If white tries to play at B to take sente, we will lives by ko or with only 2 points.](;W[rr]LB[no:A][jq:B]C[Next black will play A or B.])(;W[qr];B[pr];W[];B[qs](;W[rs];B[rp];W[qp];B[qq];W[rr];B[so];W[ro];B[sq]C[Ko.])(;W[rp];B[rr];W[so]C[White lives with 2 points.]))))(;W[om]LB[pk:A][ol:B]C[A is safer.](;B[pk];W[rq];B[nn];W[qr];B[pr];W[np];B[no];W[ol];B[qj];W[ml]LB[qs:A]C[Black still have A and white have to make his 2 groups live. So this result is good for black.])(;B[ol];W[nm]LB[qp:A][rp:B]C[A is better than B.](;B[rp];W[rk];B[sl];W[pk];B[pl];W[nk];B[ro];W[oo];B[nn];W[mn];B[no];W[mo];B[np];W[mp];B[op];W[nl];B[qp];W[ok];B[sn];W[sk];B[sm]C[White thickness is outstanding.])(;B[qp];W[rk];B[sm];W[pk];B[pl];W[nk]C[This is still good for white. Black cannot tenuki.];B[];W[oo];B[nn];W[mn];B[no];W[mo];B[np];W[mp];B[op];W[nl];B[ro];W[ok];B[sn]))))(;W[qr];B[pr];W[pn];B[on];W[rm];B[rl];W[rn];B[ql];W[rr]C[White can live this way.];B[om]LB[sl:B][ps:A]C[Black A and B are sente.];W[](;B[sl];W[];B[rp];W[qp];B[qq];W[rq];B[sm];W[sp];B[sn];W[ro];B[so])(;B[ps];W[];B[rp];W[qp];B[rs]C[Tesuji.];W[qs];B[qq];W[rq];B[sq];W[ss];B[so];W[ro];B[sp]))))(;W[ro];B[qn];W[qr];B[pr];W[rq];B[so]C[Tesuji.](;W[sp];B[qp];W[rp];B[sr];W[rn];B[rm];W[sn];B[rr];W[qq];B[qs];W[rs];B[ps];W[sq];B[sm];W[ss]C[White is completely enclosed.])(;W[rn];B[rm];W[sn];B[qq];W[qp];B[rr];W[sr];B[rs];W[sp]C[This is not good for white either.])))))(;W[](;B[jp]LB[pq:A][or:B][pr:C]C[A is the best move. B and C are bad.];W[pq]LB[oq:B][qq:A](;B[qq]LB[qp:B][oq:A][qr:C]C[A or B are possible.](;W[oq];B[qr]LB[no:B][op:A][lq:C]C[A is old-fashioned, B is slightly better but not good as well. Nowadays C is more common.](;W[op]LB[po:A][mp:B]C[A is an ancien joseki, and B is more severe.](;B[po];W[lq]C[Ancient joseki. Black wouldn't play this way now.])(;B[mp];W[po];B[qp]LB[on:B][no:A][mq:C]C[C is the best move but there's no good result for white whatever.](;W[no];B[on];W[oo];B[rn]C[Good for black.])(;W[on];B[no];W[oo];B[rn]C[Good for black.])(;W[mq];B[lq];W[mo];B[lp]C[White has a better shape than if he had played A or B.])))(;W[no]LB[po:B][mq:A]C[B is an ancien joseki.](;B[po];W[lq]C[Ancien joseki too.])(;B[mq];W[po];B[op];W[np];B[oo];W[on];B[qp];W[nq];B[nn]C[This isn't easy for white.]))(;W[lq](;B[kr];W[op]C[This move is sente.];B[po])(;B[op];W[jr]TR[oq][pq]C[The triangled stones are light.])(;B[kq];W[lp];B[op];W[kn]LB[no:2][np:1][nr:3]C[Modern joseki. White can escape. Later, 1-3 is a good sequence.];B[]C[Tenuki.];W[np];B[no];W[nr])))(;W[qp]LB[po:A][qo:B]C[A is the most common answer but B is also playable.](;B[qo];W[rp];B[rq];W[oq](;B[po];W[qr];B[rr];W[lq]LB[rs:A]C[Equal])(;B[ro];W[op];B[po];W[lq]C[Equal]))(;B[po];W[qr];B[rq];W[oq];B[rr];W[lq]C[Equal result];B[kr]C[Black can attack this way.]))(;W[qr];B[oq];W[pr]LB[qp:A][or:B](;B[qp];W[or];B[nq];W[nr];B[mr];W[rq];B[rp];W[rr]C[White's corner is small.])(;B[or];W[qp];B[rq];W[qo];B[rr];W[pn];B[oo];W[pm]C[Black's corner is big and white isn't thick.])))(;B[oq]LB[qp:C][qq:B][or:A]C[B and C are bad.](;W[or]LB[op:A][qq:B][pr:C]C[A is the best move since it allows him to choose between 2 sequences, whereas B leads to 1 sequence only. C is bad.](;B[qq];W[pr];B[op];W[qr];B[rq];W[mq]C[White isn't alive.];B[lr];W[mr];B[lq];W[mp]C[Equal result.])(;B[op]LB[pr:A][qr:B]C[If black hasn't a ladder breaker white can kosumi at B.](;W[pr]LB[qq:B][nr:A]C[Black can play A or B.](;B[qq];W[qr];B[rq];W[mq];B[lr];W[mr];B[lq];W[mp]C[Equal result.])(;B[nr];W[qp];B[qo];W[rp];B[mq]C[There's is still aji in the corner.];W[];B[rr];W[qr];B[rq];W[rs];B[sr]LB[sp:B][qq:A](;W[qq]C[The only move.];B[sp];W[ro];B[rn];W[so];B[os]C[Ko.])(;W[sp];B[os];W[ps];B[qq];W[ns]C[White is dead.])))(;W[qr]LB[qq:B][nr:A](;B[nr];W[qp];B[os](;W[pr];B[qo]LB[ro:A][rp:B](;W[ro];B[rp];W[qq](;B[qn];W[rq];B[rn];W[sp]C[Equal.])(;B[rn];W[po];B[so];W[nq];B[mr];W[mq];B[lq];W[oo];B[np];W[mp];B[no];W[lp]LB[nn:B][kq:A];B[lo]C[Tesuji];W[mo];B[nn];W[lr];B[mn];W[kq];B[kp];W[lq];B[jq];W[jr];B[ir];W[ms]C[Black is not very thick so it's an equal result.]))(;W[rp];B[ro];W[rr]LB[qr:2][os:1]C[Bad for white.]))(;W[qo];B[pr];W[qq];B[rn]C[Good for black.]))(;B[qq];W[pr];B[rq];W[mq]))))(;W[qq];B[or];W[ro];B[pn];W[rr]C[White's corner is small.])))(;B[oq];W[qk];B[](;W[qq];B[qp](;W[rp];B[ro];W[pr];B[rq];W[rr];B[sp];W[or];B[mq]C[White can live but black is too thick.])(;W[pr]LB[rq:A][or:B](;B[rq];W[or];B[nr];W[nq];B[mr];W[pq];B[op];W[rr];B[rp];W[sr]C[White is alive.])(;B[or];W[rp](;B[rr];W[rq];B[ro];W[os];B[mr];W[sr]LB[sp:B][rs:A])(;B[ro];W[rr];B[sp];W[sq]C[Ko. Normal sequence.]))))(;W[mq];B[]LB[qn:B][qo:D][ro:C][qq:A]C[A isn't a good choice. C and D are the best moves according to the situation.](;W[qq]LB[qp:B][pr:A](;B[pr];W[ro];B[qo];W[rn];B[rm];W[qn];B[pn];W[qp];B[po];W[qr]C[Black's shape has too many weaknesses.])(;B[qp]LB[or:A][pr:B]C[B is not good.](;W[pr];B[or];W[rp](;B[ro];W[rr]C[The ko is very heavy for black.];B[sp];W[sq])(;B[rr];W[rq];B[ro];W[os];B[mr];W[sr];B[rs];W[sp];B[ns];W[ps];B[lq]LB[so:A]C[This is good for black, if he plays at A later, he can make a seki in the corner.]))(;W[or]LB[nr:A][pr:B](;B[nr];W[pr];B[nq];W[mr];B[ns];W[rp];B[ro];W[rr];B[sp];W[rq]C[White is alive easily.])(;B[pr];W[nr];B[qr]C[White gets some profit but the corner is solid now. It's not good for white.]))))(;W[qn]LB[pm:A][pn:B][qo:C](;B[pm];W[rm];B[rl];W[ro];B[sm];W[rn];B[ql];W[pn];B[on];W[qp];B[qq];W[rq]C[White is alive easily.])(;B[pn];W[qo];B[po];W[rm];B[pm];W[ro]C[Good for white.])(;B[qo];W[rn];B[pn];W[ro];B[rp];W[rm]C[White gets some profit but it's still not good enough.]))(;W[ro]LB[qn:B][qo:A][rp:C]C[C is the safest move to save the corner.](;B[qo](;W[rn];B[rp];W[qn];B[pn];W[rm]C[White gets some profit but it's not good enough.])(;W[rp]LB[rn:A][qq:B](;B[rn];W[qq];B[pr];W[qr];B[so];W[pq];B[or];W[op]C[Black's shape is broken.])(;B[qq];W[rq](;B[rn];W[qr];B[pr];W[qp]C[The ko is heavy for black since his shape is thin.])(;B[qr];W[rn];B[rm];W[qn];B[pn];W[pm];B[pl];W[om];B[ql];W[rr]C[Black's shape is still bad he cannot kill white.]))))(;B[qn];W[qo];B[po](;W[qq];B[qp];W[rp];B[qr]C[White is dead.])(;W[qr];B[rq];W[qq];B[qp];W[rp];B[rr](;W[sr]C[Tesuji.];B[sq];W[rs];B[ss];W[qs];B[rn];W[sr]LB[nr:A][qs:B]C[White takes the ko first. Even if white cannot win the ko he can play at A to link the other stones thanks to B.])(;W[rs];B[sr];W[sq];B[sp];W[so]LB[nr:A][qs:B]C[Now if white loses the ko he cannot connect with A since he has no stone at B. So playing the tesuji is important.])))(;B[rp];W[qo];B[qp]LB[rm:B][pn:A]C[A or B according to the situation.]))(;W[qo]LB[po:A][qp:B](;B[po]LB[qn:B][qp:A]C[A gives to black a great influence.](;W[qp]LB[qn:B][qq:A](;B[qq];W[rq];B[qr];W[qn];B[pm];W[rm];B[rl];W[rn];B[ql];W[pn];B[on];W[rk];B[sl];W[rr];B[rs];W[sp]C[White is alive.];B[om]C[Black influence is great, this is good for black.])(;B[qn];W[qq]))(;W[qn]LB[pm:A][pn:B]C[A gives white the corner without black being thick.](;B[pm];W[pn];B[on];W[rm];B[rl];W[rn];B[ql];W[qq]C[Black is not thick, so this result is good for white.])(;B[pn];W[rm];B[pm]LB[rl:A][qp:B];W[rl];B[qp]C[Equal result. White gets profit in sente.])))(;B[qp]LB[qn:B][po:A]C[A is common mistake. B is the correct answer.](;W[po];B[oo];W[pn]C[White has a bad shape.];B[ro];W[rn];B[rp];W[qn];B[on];W[pm]C[This is very bad for white.])(;W[qn](;B[pm];W[rm];B[rl];W[oo]LB[on:A]C[Black cannot cut and A doesn't work.](;B[on];W[po];B[no];W[op];B[np];W[nq]LB[nn:A][pq:B])(;B[ql];W[on]C[Black is under attack.]))(;B[ql];W[on];B[pk]C[Fighting. Black has the corner but a floating group as well. White can be satisfied.]))))))))(;B[pn]LB[ql:A]C[The corner is weaker and white can play at A. But this move aims to the center.](;W[qq];B[pq](;W[rp]LB[rn:B][qr:A]C[Good move.](;B[qp];W[rr](;B[ro];W[pr];B[or];W[qs]C[Equal result.])(;B[qr];W[rq]LB[ro:B][pr:A]C[B is a mistake.](;B[ro];W[pr];B[or];W[qs]C[White is slightly better than if black hadn't atari.])(;B[pr];W[rn];B[rm];W[rs];B[qn];W[ro]C[Equal result.])))(;B[rn];W[pr];B[or];W[rr];B[ps];W[qr]C[Locally white isn't alive but black cannot kill.];B[sq];W[sr];B[sp];W[ro];B[so];W[qn];B[qm];W[qo];B[rl];W[po])(;B[ro];W[qo];B[rn];W[pr];B[or];W[rr];B[ps];W[qr]LB[qo:2][ro:1]C[1-2 is bad for black because of his weaknesses.]))(;W[pr];B[or];W[rr];B[ps];W[qs]C[If white has enough ko threats he can play this way.]))(;W[nq](;B[qj]LB[pm:B][qq:A]C[This is a common shape.](;W[qq];B[pq];W[pr];B[or];W[qr];B[oq];W[ro];B[rn];W[qo];B[qn]LB[po:A]C[It's better if white doesn't tenuki here.](;W[po];B[oo];W[qp]LB[on:B][np:A]C[Next black A or B.])(;W[]LB[po:A][so:B]C[A for thickness or B to kill white by ko.](;B[po](;W[];B[so];W[rp];B[ps]C[White is dead.])(;W[qp]C[If white connects here, black is very thick because he has no weaknesses at all. Black is in a good position.]))(;B[so];W[sp](;B[sr];W[qp];B[sn];W[ps];B[rp];W[rq];B[sq];W[rr]C[Ko. ])(;B[rp];W[qp];B[sq];W[sr];B[rr];W[rq];B[ss]C[Also a ko. If black wins the ko the result is almost the same but if white wins the ko, the result is different.]))))(;W[pm]LB[om:C][qm:A][on:B]C[Since black has more stones in this area, he must fight and not play too softly.](;B[qm];W[ql];B[pl];W[om];B[ol];W[qn];B[rm]LB[nm:A][po:B](;W[nm];B[rn];W[nl];B[oj]C[Joseki. Influence (in sente) vs territory.])(;W[po];B[on];W[oo];B[nm];W[qp]LB[rp:2][qq:1][nr:3]C[Good for black. Black is very thick and can still live in the corner with 1-3.];B[qq];W[rp];B[nr])(;W[qo];B[po];W[rl];B[nm];W[on];B[nn];W[oo];B[np];W[rn];B[op];W[sm];B[qm];W[rm];B[mq]C[White's terriory is too small, this is very good for black.]))(;B[on](;W[pk];B[pj](;W[ok];B[oj];W[nk];B[mi]C[Fighting style.])(;W[nk];B[oj];W[nm];B[nn];W[mm];B[lo]C[Fighting style. White destroyed some territory but black is strong than white. It's also an equal result.]))(;W[qm];B[ok];W[rp];B[qp];W[ro];B[rq];W[qk];B[pj]C[White can live with a very few points and black is thick. Good for black.]))(;B[om];W[pl]LB[on:A][qn:B](;B[on]LB[pj:B][ol:A](;W[ol];B[oj];W[ml]C[FIghting style.])(;W[pj];B[pi];W[oj];B[qk];W[ol];B[rm]C[Black is linked, and since he only has a floating group this is a bad result for white.]))(;B[qn];W[ol];B[nm];W[oj];B[ph];W[rm];B[pr]C[Fighting style.])))(;W[qh];B[];W[ql]LB[pk:A];B[pk];W[qo]LB[po:A][qp:B]C[B is bad.](;B[po];W[qp]LB[qn:B][qq:A]C[B is a mistake.](;B[qn];W[rn];B[rm];W[ro];B[qm];W[pr]C[Tesuji. Good for white.])(;B[qq];W[rq];B[rr];W[rp];B[pr];W[pl];B[ol];W[rj];B[ri];W[rk];B[qi];W[qn]C[White is alive];B[om]C[Equal result. Black has influence.]))(;B[qp];W[po];B[oo];W[qn];B[pm];W[op];B[pl];W[rp];B[rq];W[ro];B[pq];W[rr];B[sr];W[qr];B[qq];W[sp];B[sq];W[pr];B[oq];W[np];B[or];W[nr];B[ps];W[no];B[on](;W[rs]C[This move doesn't work.];B[qm];W[rm];B[sn]C[White is dead.])(;W[sn]C[The right move.];B[rs]C[White is alive. Good for white.];W[];B[rm]C[This move doesn't work.];W[qm];B[rl];W[rk];B[qk];W[sl];B[rj];W[sk]))))(;B[](;W[ql];B[];W[oo];B[po]LB[ol:B][om:A](;W[om]LB[on:A]C[Famous tricky play.];B[on];W[nn]LB[nm:A][pm:B]C[A is the right answer, B is a mistake.](;B[pm];W[pl];B[nm];W[ol];B[no];W[mn];B[np];W[mp];B[mo];W[lo];B[op];W[lp]C[Very good for white.])(;B[nm];W[ol];B[np];W[mp];B[mo]C[Good move.]))(;W[ol];B[nm](;W[nl];B[mm];W[mo];B[on];W[ml];B[lm]C[This is the right play for black, he still have the corner and he's escaping to the center.])(;W[om];B[on];W[nn];B[np]LB[mn:B][no:A]C[Tesuji. White cannot play A, he has too many weaknesses, he must play B.](;W[no];B[op];W[mp];B[mo]C[White collapses.])(;W[mn];B[oq];W[ml];B[lq]C[Good for black.]))))(;W[pr];B[qq];W[no];B[];W[ql];B[];W[ol];B[qr];W[qo]LB[rn:B][po:A]C[B is the best answer.](;B[po];W[qn];B[pm];W[rk]C[Good move.];B[or])(;B[rn](;W[po];B[ro];W[oo];B[qn])(;W[qn];B[ro]C[Black is comfortable.])))(;W[qj](;B[];W[ro]LB[qm:B][rp:A][qq:C](;B[rp]LB[qo:B][qq:A](;W[qq];B[qp];W[pq];B[ql]C[Equal result.])(;W[qo];B[qp];W[qm];B[oq];W[np]C[Equal result.]))(;B[qm];W[pq])(;B[qq];W[qm]C[White is comfortable.]))(;B[ql];W[kp];B[]LB[rn:A];W[rn](;B[qn];W[qq];B[pq];W[rp]C[White is alive easily.])(;B[qk](;W[pj];B[qq]C[White's stone is dead.])(;W[qq];B[pq];W[qp];B[pj]C[White gets the corner but black attacks the white stone.])))))(;B[pd];W[ql]LB[qi:A][oq:B]C[A is correct whereas B is too soft.](;B[oq];W[np];B[qn]C[Black gets the corner but playing this way is too soft.])(;B[qi]C[This is the right move, black doesn't have to be afraid.];W[ol];B[nn]C[White has 2 unsettled groups and black 3 stones are strong.]))(;B[oq];W[np]LB[qj:B][jp:A](;B[jp];W[];B[qj];W[qq]LB[qp:A][or:C][pr:B](;B[qp];W[or](;B[pq];W[lp]LB[qr:A]C[Later white A is good.])(;B[pr];W[pq];B[qr];W[op];B[rq]C[White's shape is strong.]))(;B[pr];W[qo];B[po];W[qn];B[qm];W[rm];B[ql];W[rr];B[nr];W[lq]C[Black gave up the corner but he can attack white very severly now.])(;B[or];W[qo];B[po];W[qn];B[qm];W[rm];B[qp];W[rp];B[rq];W[ro];B[qr];W[sq];B[rr];W[ql];B[pm]C[White's groups aren't alive yet. Good for black.]))(;B[qj]LB[kq:A];W[kq];B[]LB[ko:A];W[ko];B[]LB[ql:B][qq:A]C[Invading at B is better than A, otherwise black will keep the corner while making white overconcentrated.](;W[qq]LB[qp:C][or:A][pr:B]C[A is bad, B is even worse since the white's group is already alive and not attackable. C is the best move.](;B[or];W[qo];B[po];W[qn];B[qp];W[rp];B[qm];W[rr];B[rm];W[so]LB[pm:A][iq:B]C[Good for white. White is alive and black has a cutting point at A. But with a stone at B, black can still attack white's group.])(;B[pr];W[qo];B[po];W[qn];B[qm];W[rm];B[ql];W[rr];B[nr];W[mr]LB[iq:A]C[Black cannot attack white's group even with a stone at A, because he's too strong. So black's stones are useless.])(;B[qp];W[or]LB[pq:A][pr:B]C[A leaves some aji in the corner, B is better.](;B[pq];W[pr];B[qr]LB[rq:A][rr:B]C[There's still aji.](;W[rq];B[rr];W[qn]C[Example 1.])(;W[rr];B[rq];W[qs]C[Example 2.]))(;B[pr];W[pq];B[qr];W[op];B[rq]C[This is the best result for black. Black has the corner, white is thick but the white's group was already alive, white is even overconcentrated.])))(;W[ql];B[pk];W[qo];B[po]LB[qn:A][qp:B]C[A is better.](;W[qn];B[qp];W[pl];B[ol];W[rj];B[ri];W[rk];B[qi];W[rm]LB[ro:A]C[If black plays at A, he will be gote.];B[ro];W[rn];B[rp])(;W[qp];B[qq];W[qn]LB[pm:B][rp:A]C[A is the correct move.](;B[rp];W[ro];B[rq];W[pl];B[ol];W[rj];B[ri];W[rk];B[qi];W[rm]C[White is alive in gote, this is not the best sequence for him.])(;B[pm];W[rq]C[This is painful for black.]))))))(;W[];B[qk];W[];B[ok];W[](;B[kp];W[pq]LB[oq:B][qq:A]C[A is the correct answer. B is a mistake, white can live in the corner.](;B[oq];W[qq];B[or];W[ro](;B[qp];W[rp];B[rr];W[rq];B[qr];W[pr];B[ps];W[qn];B[pm];W[rm];B[rl];W[sn]C[White is alive. Good for white.])(;B[rn];W[qo];B[qn];W[po];B[oo];W[qp];B[op];W[pr]C[White is alive. Black is overconcentrated.]))(;B[qq]LB[oq:A][qr:B](;W[qr];B[qp];W[oq];B[rr];W[mq];B[lq];W[lo];B[ko];W[ln];B[kn];W[lm]C[Equal result, black can chase white even if white has destroyed some territory.])(;W[oq];B[qr];W[op];B[po];W[mq];B[lq];W[lo];B[ko];W[ln];B[kn];W[lm]C[Equal result as well.])))(;B[lp];W[];B[ln];W[qq];B[pq];W[qp]LB[qo:B][ro:A]C[Since black is very strong outside he must play A, B is bad since it leads to a ko.](;B[ro]C[Severe move.];W[qo];B[qn];W[rp];B[rr];W[qr];B[rn];W[pr];B[or];W[oq];B[nr];W[po];B[op];W[oo];B[np];W[no];B[mp];W[om];B[nm];W[on];B[ol];W[pm];B[ql]C[White is dead.])(;B[qo];W[pr];B[or];W[rr];B[ps];W[qs]C[Ko.])))))