(;GM[1]FF[4]CA[UTF-8]AP[CGoban:3]ST[2]
RU[Japanese]SZ[19]KM[0.00]
PW[Piao Wenyao]PB[Kim Chi-seok]WR[9p]BR[7p]RE[B+0.50]
;B[pd]
;W[dq]
;B[qp]
;W[dd]
;B[do]
;W[co]
;B[cn]
;W[cp]
;B[dm]
;W[fq]
;B[cf]
;W[fc]
;B[di]
;W[qj]
;B[oq]
(;W[qf]
;B[nc]
;W[rd]
;B[qc]
;W[ph]
;B[cc]
;W[cd]
;B[bd]
;W[be]
;B[bc]
;W[ce]
;B[eb]
(;W[ec]C[This position is taken from a professional game, Piao Wenyao vs. Kim Chi-seok.
I had seen this game on the excellent Go Game Guru website, gogameguru.com .
The commentary (by Baek Seongho 9p) did not mention why White must
extend with 28 (as here) instead of blocking, (see variation) so I asked my teacher,
Li Ang 3p (*) , about it.

* Li Ang teaches on KGS and has a website at www.lweiqi.com.])
(;W[fb]C[After 27 an interesting position was reached. If White blocks to the right of 27, and Black pushes up and cuts with 29 and 31 , this normally creates
a life and death problem (see the variations after 32), and the swordsman dies in the corner.

However, in this case, due to the position of the stones on the outside, it might be possible to cut and live, therefore White has to play to avoid this.

I asked ‘Why can’t White block?’ and Li Ang answered by presenting this variation.

Some players, probably including me, would have blocked and not seen the impending doom.]
;B[ec]
;W[ed]
;B[fd]
;W[hc]
(;B[df]
;W[fe]
;B[gd]
;W[ef]
;B[hd]
;W[ic]
;B[id]
;W[jc]
;B[bf]
;W[ea]
;B[dc]
;W[ae]
;B[da]LB[fc:B][id:C][fe:A]C[After this sequence, the white group A etc. is particularly weak and the
black cutting stones C etc. will escape easily.

Li Ang commented that Black must win the game from this position.])
(;B[]
;AE[nc][qc][pd][rd][qf][ph][di][qj][dm][cn][co][do][cp][qp][dq][fq][oq]AW[df]TR[hc][df]C[Here is the life and death problem I had in mind. With the marked stones in place, White can kill.]
;W[ea]
(;B[ad]
;W[ab]
;B[ba])
(;B[ca]
;W[ad]
;B[ab]
;W[ba]
;B[bb]
;W[db]
;B[dc]
;W[da]
;B[cb]
;W[fa])
(;B[ab]
;W[ba]
;B[ad]
;W[dc]
;B[cb]
;W[ca]
;B[db]
;W[da])
(;B[ba]
(;W[ab]
(;B[da]
;W[dc]
;B[db]
;W[cb]
;B[ca]
;W[bb]
;B[fa])
(;B[db]
;W[da]
;B[ca]
;W[bb]
;B[fa]
;W[ea]))
(;W[ad]
;B[ab]
;W[cb]
(;B[db]
;W[dc])
(;B[ca]
;W[dc]))))))
(;W[bd]C[Lyonweiqi [3p\]: better play here]))
