(;GM[1]FF[4]CA[UTF-8]AP[CGoban:3]ST[2]
RU[Japanese]SZ[19]KM[0.00]
PW[White]PB[Black]
;B[pd]
;W[dd]
;B[pp]
;W[dp]
;B[fq]
;W[hq]
;B[cq]
;W[dq]
;B[cp]
;W[do]
;B[dr]
;W[er]
;B[cr]
;W[eq]
;B[cn]LB[cl:C][em:B][bn:E][kq:A][nq:D]C[The sequence up to Black 15 in the lower left corner is a joseki that often appears in actual games. White can consider three continuations: A, B and C.
D is a bad move for White, and E a trick move. We are going to study how to handle these moves.
We are also going to look into how Black can play after the joseki in the lower left corner finished (after the joseki).]
(;W[kq]C[This move is famous because it is often played by Lee Changho 9P. It is slow but solid.]
(;B[qn]C[Black answers with a knight's enclosure.]
(;W[nc]C[White approaching on the upper side is an easy way to play.]
;B[qf]
;W[pb]
;B[qc]
;W[kc]
(;B[cf]
;W[fd]
;B[bd]
;W[cc]
;B[dh]LB[cn:A]C[Considering the balance of low and high moves, Black played on the fourth line. ("A is low, so black plays high on the 4th line here)]
(;W[em]C[This is a nice point.])
(;W[]C[If White doesn't play here,...]
;B[fo]
;W[gp]
;B[dn]LB[dn:3][en:A][fo:1][gp:2]C[Black will use the combination of Black 1 and Black 3 to flatten the lower white side and improve Black's framework.

White can't hane at A because...]
;W[]
;B[eo]LB[eo:A][fr:B]C[... Black A is sente anytime: if White plays elsewhere, Black will capture at B.  Since it is sente anytime, Black doesn't exchange Black A for White B. ]))
(;AW[cf]LB[cf:A]C[If there is a white stone at A, ...]
(;B[dn]C[This move is not good because it helps White to become stronger.]
;W[en]
;B[em]
;W[fn]LB[dm:A]C[White got strong, but Black still has to worry about his weak point at A.])
(;B[cm]LB[ch:A][fo:B]C[Black's best move is quietly reinforcing here.
Next Black can aim at A or B.])))
(;W[cl]LB[bo:A]C[White can also approach here aiming at A.]
(;B[dn]C[Playing here starts a little complicated variation.]
;W[en]
;B[em]C[White has two options to answer.]
(;W[fn]
;B[dl]
;W[dk]C[Now Black has to be careful.
]
(;B[ck]C[This is a mistake.]
;W[cj]
;B[bk]
;W[dj]
;B[bj]
;W[el]
;B[dm]
;W[fm]LB[co:1]C[Since blocking here becomes sente for White, Black failed.])
(;B[fm]C[That's why Black should push once more to prevent White's blockade.]
(;W[gn]C[If White extends, ...]
;B[ck]C[Black will cut to capture.])
(;W[gm]C[If White plays hane here, ...]
;B[fl]LB[ck:B][gn:A]C[Black will answer here. Even though it is an empty triangle, it's a good move here because A and B become miai.]
(;W[gn]
;B[ck])
(;W[cj]
;B[gn]
;W[fp]
;B[go]
;W[gp]
(;B[bn]TR[gn][go]C[It's not urgent for Black to save the two black stones.])
(;B[]
;W[bo]
;B[co]
;W[bn])))))
(;W[dm]
;B[bm]
;W[fn]
;B[el]
;W[cj]LB[cm:1][bn:2]C[White doesn't need to exchange White 1 for Black 2 because it is sente anytime.]
;B[dl]
;W[co]
;B[bo]
;W[cm]
;B[bn]
;W[dk]))
(;B[cm]C[This is a simple and clear move.]
;W[dl])))
(;B[]
;W[qn]C[This is a nice place for White too. If Black doesn't play here, White will play here.]
;B[nq]
;W[rp]
;B[qq]
;W[rq]C[White is happy.]
(;B[rr]
;W[pr]
;B[qr]
;W[oq]
;B[op]
;W[nr])
(;B[nn])))
(;W[nq]C[It's not good to approach from this side.
]
;B[qn]
(;W[pr]
;B[qq]
;W[lp]
;B[jq]C[Later Black can invade here and White won't be able to capture him.
]
;W[jp]
;B[fr]LB[jq:A]C[When there is a black stone at A, this place becomes a weak point in White's shape.
]
;W[fs]
;B[kq]
;W[kp]
;B[iq]
;W[ip]
;B[hr])
(;W[no]C[This move looks strong, but it is too slack.]
;B[pr]C[This move is urgent, it prevents white from invading at 3-3.]
(;W[or]
;B[oq]
;W[nr]
;B[ip]C[The shoulder hit is the vital point regarding the joseki in the lower left corner.]
;W[iq]
;B[jp]
;W[hp]
;B[in]
;W[ho]
;B[km]C[After Black got the lower right corner, he also succeeded in reducing White's framework.
])
(;W[jp]C[Now  defending ...]
;B[nr]C[... gives Black a big endgame move here. White's territory is not that big.]
;W[mr]
;B[oq])
(;W[]
;B[jq]LB[jo:A][lq:B][fr:C]C[If White doesn't defend, Black will invade giving White a hard time. Black can continue at A, B or C to handle this situation. White has the thinner shape.])))
(;W[qn]C[White can also approach from this side.]
;B[nq]
;W[rp]
(;B[jq]C[This is a big point. Lee Changho 9P chose the two-space extension to avoid this scenario.]
;W[qq]C[Black has two ways to answer.]
(;B[fp]C[In this situation this is a nice move.]
;W[gr]
;B[hp]
;W[iq]
;B[ip]
;W[jr]
;B[kq]
;W[kr]
;B[lq]C[Up to here Black gained thickness and influence.]
(;W[dn]C[For White it's good to play here.]
;B[cm]
;W[fn])
(;W[]C[If he doesn't play here,... ]
;B[fr]
;W[fs]
;B[dn]C[... this black move will become sente, (white needs to live) and give Black major influence. This is too good for Black.]))
(;AB[pj][cm]LB[pj:A][cm:B]C[If there is a stone at A and B....]
;B[fr]C[... playing here will be forceful too]
;W[fp]
;B[gp]
;W[gq]
;B[es]LB[pj:A]TR[gp]C[White can't capture the marked stone thanks to the ladder breaker at A.])
(;B[fr]
;W[fp]
;B[gp]
;W[gq]
;B[fo]
(;W[ep]C[This move causes big trouble for White.]
;B[es])
(;W[fs]C[But White can play here.]
;B[ep]
;W[gr]C[Since there wasn't big territory for White, Black didn't gain much here.])))
(;B[qq]LB[qk:A][lq:B]C[Black can also answer here. However it gives White the chance to choose between the normal joseki move (extension at A) and the approach on the bottom at B.]
(;W[qk])
(;W[lq])))
(;AW[kp][np][pp]TR[np][pp]C[ If there is a nice shape on the lower side, ...]
;W[em]C[This is an excellent move to expand White's framework.]
(;B[cm]C[After Black calmly answers, ]
;W[]
;B[gm]C[...he can later aim at this point, the weak point of White's shape.])
(;B[]
(;W[cm]C[If Black plays elsewhere, White can utilize with this move in sente.]
;B[bn])
(;W[cl]C[This move has both merits and demerits. It is gote but aims at a nice follow up.]
;B[]
;W[bo]
;B[co]
;W[bn]
;B[bp]
;W[cm]
;B[ar])))
(;AW[np][pp]
;W[cl]TR[np][pp]C[When White's shape is good, ...]
(;
;B[dn]C[Playing this way will make White's territory more solid.]
;W[en]
;B[em]
;W[fn])
(;B[cm]C[It's better to play here to take sente.]
;W[dl]
;B[ip]C[Regarding the joseki in the lower left corner, this is the vital point for reducing White's shape ]
;W[iq]
;B[jp]
;W[hp]
;B[in]
;W[ho]
;B[km]))
(;W[bn]C[This is a trick move. Be careful not to fall into the trap!]
(;B[cm]C[Oh, no! This is just what White dreamt of!]
;W[co]C[Black is in big trouble because White cuts Black.])
(;B[bm]C[This move looks forceful, but...]
;W[cm]C[White will cut to utilize Black's weaknesses.]
(;B[co]
;W[bl]
;B[dn]
;W[fp]C[White is solid on both sides. White's trick move succeeded.])
(;B[bo]
;W[dn]
;B[an]
;W[cl]C[Good for white, black is flattened]))
(;B[co]C[This is the correct move to properly handle White's trick play.]
;W[cm]
;B[dn]
;W[fp]LB[cl:A][dn:B]C[White gained a little profit on the left side (compared to White's usual approach at A) but Black pushing out at B is painful for White. It makes White weaker because it reduces White's liberties. Furthermore the two white stones on the left are vulnerable to attack.])))
