(;GM[1]FF[4]CA[UTF-8]AP[CGoban:3]ST[2]
RU[Japanese]SZ[19]KM[0.00]
C[The way to attack two space extention and answer ]
(;B[pd]
(;W[dd]
;B[qp]
;W[dp]
;B[op]
;W[qj]
;B[qh]
;W[qm]C[Black can tenuki, but in this opening, black normally attacks the white's two space extention. how?

There are normally five ways to attack. ]
(;B[rk]C[one possibility, but not good in this situation]
;W[rj]
;B[ql]
;W[pl]
;B[rm]
;W[qk]
;B[rl]
;W[qf]C[white can invade here, blacks choice of invasion was not good in this case.])
(;B[rl]C[other direction]
;W[ql]
;B[rk]
(;W[qk]
;B[rj]
;W[qi]
;B[ri]
;W[ph]
;B[pg]
;W[qg]
;B[rh]
;W[oh]C[too low for black])
(;W[qi]C[sometimes white can play this move]))
(;B[oi]C[second attack]
(;W[oj]
;B[nj]
;W[ok]
;B[ni]
;W[ml]C[white is safe, but blacks shape is strong])
(;W[ok]C[not a good answer]
;B[pl]C[vital point])
(;W[ol]C[good answer]
;B[pk]C[it doesn't work now]
;W[pj]
;B[ok]
;W[oj]
;B[nk]
(;W[nj]
;B[qk]
;W[mk]
;B[nl]
;W[rk]
;B[rl]
;W[rj]
;B[ql]
;W[qf]C[White can play this way])
(;W[qk]C[Blocking here is not good.]
;B[nj]
;W[pl]
;B[mm]C[This is good for black, its difficult for white to get out and he needs to create eyes.]))
(;W[om]C[not good]
;B[ok]LB[pl:A]C[this move aims to play at A ]
;W[pk]
;B[ol]
;W[pl]
;B[nm]))
(;B[oj]C[third one, but only good if black is stronger at the top]
;W[pi]C[The black's shape should be much stronger on the top to be able to play this])
(;B[pl]C[5th one,  normal and good move]
(;W[ql]
(;B[pj]C[block]
(;W[pi]C[not good]
;B[qi]
;W[pk]
;B[oj]
;W[ok]
;B[nj]
;W[nk]
;B[rj]
;W[qk]
;B[mj]C[good for black ])
(;W[qi]
;B[pi]
(;W[rh]
;B[rg]
;W[qg]
;B[ph]
;W[rf]
;B[qk]C[good for black])
(;W[pm]C[sometimes it is possible]
;B[ol]
;W[rh]
;B[rg]
;W[ri]
;B[qg]
;W[ro]))
(;W[pk]C[normal answer]
;B[ok]
;W[qk]
;B[pi]
;W[ol]
;B[nk]
(;W[om]C[normal answer]
;B[jc]C[easy opening for black])
(;W[jc]C[if tenuki]
;B[om]C[painful for white, but sometimes playable.]
(;W[pm]C[Don't capture this stone, it is a bad move. It loses aji: Aji-keshi]
;B[nm]
;W[ro]
;B[rp]
;W[ri]
;B[rn]
;W[rh]
;B[rg]
;W[rm]
;B[qo]
;W[rk]C[Very painful for white to live like this])
(;W[ro]LB[nl:A]C[White should play here. Keeping the aji of white A for later]
;B[rp]
;W[qo]
;B[po]
;W[ri])
(;W[nl]
;B[pm]
;W[ml]
;B[ro]
;W[rh]
;B[rg]
;W[ri]
;B[mk]
;W[nn]
;B[po]
;W[qg]
;B[qf]
;W[pg]
;B[re]
;W[ni]C[Very big fight. We attached some pro games with this opening.]))))
(;B[pk]C[in different position, this move possible]
(;W[pj]
;B[qk]
;W[rk]
;B[rl]C[fighting but not easy for black in this position]
;W[rj]
;B[rm]
;W[qg]C[In this case white can settle himself with this nice attachment. We attached some pro games in the bonus tabs for positions where this attack is good for black.])
(;W[pm]C[white can play this way]
;B[pj]
;W[qi]
;B[pi]
;W[rh]
;B[rg]
;W[ri]
;B[qg]
;W[nm])
(;W[ri]C[white can play this way too]
(;B[pj]
;W[qi]
;B[pi]
;W[rh]
;B[qg]
;W[rg]
;B[qf]
;W[jc])
(;B[rh]
;W[pj]
;B[oj]
;W[pm]))))
(;W[pm]C[White can think of fighting here]
;B[ql]C[cut]
;W[ol]
(;B[pk]C[bad shape]
;W[rl]
;B[rk]
;W[rn]
;B[sl]
;W[rm]
;B[pj]
;W[nn]LB[qj:A]C[Black didn't get much.]
;W[qf]
;B[]
;W[rj]
;B[qk]
;W[rh])
(;B[rm]C[Black can fight this way]
;W[rn]
;B[rk]))))
(;W[dc]C[another game

b:Park Jin-sol
w:Yoo Chang-hyuk]
;B[pp]
;W[cp]
;B[eq]
;W[do]
;B[iq]
;W[cf]
;B[ic]
;W[nc]
;B[oc]
;W[nd]
;B[pf]
;W[kc]
;B[fc]C[How will white attack the black group?]
(;W[gd]C[White can think this move.]
;B[gc]
;W[id]
(;B[hd]
;W[he]
;B[hc]
;W[jd]
;B[ge]
;W[hf]
;B[fe]
;W[ed]
;B[fd]C[good for white])
(;B[fd]C[good answer]
;W[hd]
;B[jc]
;W[jd]
;B[dd]
;W[cd]
;B[cc]
;W[db]
;B[ce]
;W[bd]
;B[de]
;W[be]
;B[df]
;W[cg]
(;B[cb]
;W[bb]
;B[eb]
;W[bc]
(;B[kb]
;W[lb]
;B[jb]
;W[ld]
;B[ke]
;W[kd]C[black has sente]
;B[qi])
(;B[ec]))
(;B[eb]
;W[cb]
;B[ec])))
(;W[je]C[good attack]
;B[ge]
;W[if]LB[hd:A]C[aims to play at A ]
;B[ee]
;W[cd]
;B[qj]
;W[ff]
;B[gf]
;W[hd]
;B[fg]
;W[ef]
;B[fe]
;W[eg]
;B[fh]
;W[hc]
;B[eh]
;W[ch]C[white's attack succeeded])))
(;B[qd]C[Let's see the professional game.

B:Rin Kaiho 9p
W:Lee chang-Ho 9p]
;W[dd]
;B[pq]
;W[oc]
;B[ld]
;W[dp]
;B[pc]
;W[qk]
;B[qi]
;W[qo]
;B[qm]
;W[oo]
;B[mq]
;W[pl]
;B[qp]
;W[ro]
;B[od]
;W[fc]
;B[cj]
;W[cl]
;B[cg]
;W[ce]
;B[fq]
;W[dq]
;B[ip]TR[cg][cj]C[how will you attack the marked stone?]
(;W[bi]C[not good]
;B[bj]
;W[ch]
;B[dh]
;W[bg]
;B[ci]
;W[bh]
;B[cn])
(;W[dh]LB[cn:A]C[White needs to defend against the black invasion at A.
This is a good move.]
;B[ch]
;W[dj]C[How will black answer? 

]
(;B[dk]C[not good]
;W[ck]
;B[di]
;W[ej]
;B[ei]
;W[fj]
;B[fi]
;W[bj]
;B[ci]
;W[gj])
(;B[di]
;W[ei]
;B[ci]
;W[dk]
;B[eh]
;W[fi]
;B[eg]TR[fc][dd][ce]C[normal, but the marked stones are too strong.])
(;B[ck]C[good answer]
;W[dk]
;B[dg]
;W[eh]
;B[bl]
;W[bm]
;B[bk]
;W[cm]
;B[bf]C[if white blocks, black lives in sente]))))