(;GM[1]FF[4]CA[UTF-8]AP[CGoban:3]ST[2]RU[AGA]SZ[19]KM[7.50]GN[R1 British Championship Title Match]PW[Yaoling Yang]PB[Ho-Yeung Woo]WR[7d]BR[6d]PC[https://online-go.com/review/1332425]RE[W+0.50];B[pd];W[dc];B[pp];W[dq];B[co];W[dl]
(;B[dn];W[fp];B[bq]
;W[ip]C[Move number 7 was a bit unusual. Up to here, it's considered as a favorable result for White.];B[ce];W[ch]
(;B[fd];W[de];B[dd];W[ed];B[cd];W[ec];B[ee];W[df];B[cc];W[fc]
;B[fe]
;W[hc]C[Move 13 was also unusual. So, up until now, I felt like I was seeing a 1960s game!];B[bg];W[cf];B[bf];W[eh];B[he];W[jd];B[gh];W[bh];B[je];W[ke]
;B[jf]
;W[ld]LB[ld:4][je:1][ke:2][jf:3]C[This exchange was a bit questionable. It strengthens Black's middle group but pays points on the top. Black could have skipped this exchange since Black's middle group was stable.];B[kq]
(;W[kf]
(;B[ek]
(;W[cb];B[bb]
;W[bc]LB[bb:4][cb:3][bc:5][kf:1][ek:2]C[However, White resisted and started this complicated ko.

It wasn't easy to determine the meaning of all three moves (moves 1, 2, and 3), and I still can't understand them.];B[bd];W[ab];B[ac];W[ba];B[aa];W[el]
(;B[gk];W[ab];B[fl];W[bc];B[hq];W[ad]
;B[go]C[Even though Black got an advantage on the lower side, White took so many points and cleared up the left side group's life-and-death issue that the game must be favorable for White.
However, handling the lower White's group isn't easy.]
(;W[gp];B[hp];W[ho];B[iq];W[gn];B[fo];W[eo];B[fn];W[en];B[fm]
;W[em]C[White has made a clear connection but made bad exchanges to make Black's outside big and strong.];B[cm];W[qf];B[qe];W[pf];B[oc]
(;W[qn];B[pn]
(;W[qo];B[qp];W[pm];B[on];W[om];B[nm];W[nl];B[qm]
(;W[rp]C[This White's move was a sensitive move. If White skips this move...]
(;B[po]
(;W[rq]C[Therefore Black couldn't resist and let White take the corner. However, White's 84 was a big mistake. ];B[rm];W[so];B[sn];W[ro];B[qr];W[pk];B[qj];W[qq];B[pq];W[rr]
;B[pr];W[rs];B[ml];W[mm];B[nn];W[mk];B[ll];W[nk]
;B[qh]C[Up until this, Black paid only the tiny corner, kept the lower side's potential, and took over the right side.];W[lk];B[kl];W[kk];B[jl];W[rf]
(;B[ri]C[At this point, both players seem aware of the game situation. Therefore, Black played passively, and White overacted, which created some mistakes. 
];W[rd];B[re];W[se];B[rc];W[qd];B[qc];W[pe];B[mc];W[pi];B[pj]
;W[oj];B[rk];W[lb];B[mb];W[od];B[pc]
(;W[hg];B[gg];W[jg];B[bk];W[gr];B[ep];W[cp];B[bp];W[eq];B[gq]
;W[fq];B[hr];W[hs];B[jr];W[fj];B[fk];W[er];B[do];W[dp];B[cr]
;W[dk];B[ej];W[bj];B[ck]
;W[dj]C[There were some ups and downs, but Black maintained a decent lead up to now. However, suddenly, White made many points in the middle. 
Now, look at the middle area. It's small, but it's a collision area, so Black should have played there first.]
(;B[cj];W[ei];B[gj];W[hi];B[hh];W[ih];B[hf];W[ik]
;B[il]C[Since White takes the middle and reduce Black's middle potential, White made a close game.];W[nd];B[ph];W[sc];B[rb];W[oh];B[lc];W[kb];B[kc];W[jc]
(;B[ig]LB[ij:A]C[And this capture was the losing move. It looks obvious sente exchange. However, it blocks another endgame A]
(;W[nc];B[nb];W[sb];B[pb];W[ql];B[rl];W[rn];B[sm];W[rg];B[rh]
;W[ii];B[ci];W[di];B[bi];W[ah];B[jk]
;W[jj]C[After White cleared up the middle like this, both players made a good endgame, and White saved this game by just a half point. ];B[md];W[me];B[kd];W[le];B[hd];W[id];B[la];W[ib];B[ka];W[jb]
;B[is];W[ie];B[if];W[oa];B[pa];W[cl];B[bl];W[hk];B[hj];W[ij]
;B[hl];W[gs];B[gi];W[jh];B[pg];W[og];B[ef];W[eg];B[ma];W[qs]
;B[ps];W[dm];B[bm];W[ai];B[aj];W[gd];B[ge];W[gc];B[ds];W[es]
;B[ja];W[cq];B[br];W[ia];B[dr];W[ra];B[qa];W[sh];B[si];W[sg]
;B[sa];W[sd];B[fi];W[fg];B[ff];W[oi];B[qi];W[pl];B[qk];W[ra]
;B[ne];W[oe];B[sa];W[ak];B[al];W[ra];B[ok];W[ol];B[sa];W[sj]
;B[sk];W[ra];B[sq];W[sr];B[sa];W[jp];B[jq];W[ra];B[cg];W[be]
;B[sa];W[js];B[ks];W[ra];B[fr];W[fs];B[sa];W[bo];B[cn];W[ra]
;B[dh];W[dg];B[sa];W[ob];B[na];W[ra];B[ag];W[af];B[sa];W[ob]
;B[oa];W[ra];B[fh];W[sa];B[qg];W[];B[];W[])
(;W[ii];B[jk];W[jj];B[hj]
;W[ij]C[Eventually, this reuslt came. However...]))
(;B[ci];W[di];B[bi];W[ah]
;B[ij]LB[ah:4][bi:3][ci:1][di:2][ij:5]C[First, Black should exchange 1-4. And then had to play this clamp first before capturing. ];W[jj];B[ig]
;W[ii]LB[ig:7][ah:4][jh:A][bi:3][ci:1][di:2][ii:8][ji:10][hj:9][ij:5]
[jj:6][jk:B]C[When White needs to block at 6, Black captures at 7. After 8, can you see the difference between this and the former diagram?
Since 5,6 are exchanged, Black can connect at 9 to look for an A cut. So when White removes A with 10, Black has a B cutting point! That's a huge difference, and it turns into a game difference!]))
(;B[ii];W[jj]
;B[ij]C[Like this.]))
(;W[cl]C[This was the biggest point move.]))
(;B[pj]LB[ol:A]C[Black can push here to aim the A weakness to quickly settle the right side group while reducing White's potential in the middle.]))
(;W[rm];B[ql];W[mm];B[nn];W[rl];B[ol];W[qk];B[pl]
;W[rq]LB[nl:A][mm:B]SQ[om][pm]C[It's very challenging to imagine, but if White sacrifices the two stones in the middle and smoothly takes over the corner while keeping the left side, it is profitable. Instead, it looks like Black can expand the potential as Black took two stones in the middle, but since White's A and B are still functioning, the potential is limited. Now, when we see this case with a clear view, the captured area doesn't look connected to Black's middle potential much.
In this case, White can keep the lead.]))
(;B[rq];W[ql];B[rm];W[rl];B[ml];W[nn];B[mm];W[po];B[oo];W[op]
;B[no]
;W[rn]LB[rp:A][rq:B]C[However, if White already has an A,B exchange, White can create more weaknesses in Black's shape, so Black must pay a lot more.]))
(;W[ql];B[rm];W[rl];B[ml];W[nn];B[mm];W[po];B[oo];W[op];B[no]
;W[rn]
;B[rp]C[When White tries to use Black's thinness on the lower right corner, Black can descend at S4 to clear up the case..]))
(;W[pm];B[on];W[qq];B[pq];W[qp];B[qm];W[po];B[oo];W[qo];B[pl]
;W[kj];B[om];W[jg];B[qr];W[rr];B[pr];W[rm];B[rl];W[sn];B[rs]
;W[sr];B[sl]
;W[sp]C[However, when the situation goes similarly, Black has a bunch of sente moves to strengthen the outside and get profit from threatening the lower right corner group.]))
(;W[pn]TR[pn][pp]C[I often recommend people not to approach high against a Star point. But this case was exceptional.];B[on];W[om];B[nn];W[qq];B[pq];W[qp];B[po];W[qo];B[pm];W[qn]
;B[ol];W[kj];B[nm]
;W[jg]LB[jg:15][kj:13][ol:12][nm:14][om:3][pm:10][nn:4][on:2][pn:1]
[qn:11][po:8][qo:9][qp:7][pq:6][qq:5]C[In this case, White doesn't have a burden to use a ladder breaker 13 to erase Black's potential because White's lower right corner group is fine.]))
(;W[en]
(;B[fm];W[fn];B[gn]
;W[em]LB[em:5][fm:2][en:1][fn:3][gn:4][iq:A]C[Instead, White's 1 was the correct move. Then White can still connect like the actual game without making bad exchanges. Later, White could still move White's one stone with A.])
(;B[eo];W[fo];B[fn];W[gn];B[em]
;W[gp]C[If Black resists, White can connect to another side, and Black wouldn't have enormous potential.])))
(;B[db];W[fk]
;B[nc]C[If I were Black, I would have cleared up the ko and quickly taken sente.];W[jg];B[ig];W[ih];B[jh];W[kg];B[ii];W[hh];B[hi];W[hg];B[gg]
;W[if];B[hf];W[ig]
;B[fi]C[If White tries to attack the middle group, sacrifice some stones but keep making connections to avoid complexity.]))
(;W[dk]C[If White responds calmly, it removes Black's invasion, so it can be a satisfactory result for White. ]))
(;B[di];W[dh];B[ck];W[cl]
;B[dk]C[Black can even enter like this to split White's groups. ]))
(;W[cm]C[This place is a guaranteed spot. White can stabilize the left side group and also threaten Black's base. However, both players focused more on the middle.]))
(;B[ed];W[ec];B[fd];W[gb];B[eh];W[cm];B[hc]))
(;B[ep];W[dp];B[do];W[eo];B[eq];W[er];B[fr];W[dr];B[en];W[fo]
;B[gp];W[go];B[hp];W[ho];B[ip]
;W[bp]C[Therefore, often Black covers at E4 and if White resists, a difficult pattern comes.]))
