(;GM[1]FF[4]CA[UTF-8]AP[CGoban:3]ST[2]
RU[Japanese]SZ[19]KM[0.00]
PW[Chen Yaoye]PB[Park Junghwan]C[This opening comes from a 2010 game between Park Junghwan and Chen Yaoye.  An interesting hane comes up twice, in two corners.  But actually a second move, a solid connection instead of a tiger's mouth may be the key to this game. In both corners it changes the result significantly.]
;B[pd]
;W[dd]
;B[pq]
;W[dp]
;B[fq]
;W[cn]
;B[qk]
;W[jp]LB[eq:A]C[White can of course also choose to bump at A first and then pincer, both this move and A are fine choices.]
;B[dr]
;W[gq]LB[gp:C][hp:B][cq:A]TR[jp]C[When I do search I see this move showing up twice in 2000, then in 2005 it starts appearing regularly.  This attachment is the planned follow up to the triangled pincer.  A move a the 3-3(A) to defend the corner would be slack here, after black B black has a stable position, and the function of the pincer is not clear.  The classic black response to this attachment was at C, but actually professional consensus is this is a bit slow for black.  See the variation for a continuation from C.]
(;B[fp]
;W[fr]
;B[er]
;W[gr]LB[hr:A]TR[dp]C[Allowing this sequence appears to violate Go principals, as the triangle stone sits on the vital point of black's shape.  In recent games(3 examples in 2012) white plays A instead.  It loses a bit on the edge in the end game, but is thicker.  In this game Park used the weakness from this solid connection to turn the game around.]
;B[cp]C[Black must attach here.  Playing at the 3-3 and letting white make a solid block is not enough for black.]
;W[cq]C[Of course white will hane here.]
(;B[bq]LB[bp:A]TR[pd]C[And here is the first instance of the powerful hane.  It depends on a black ladder breaker around triangle.  If black does not have the ladder breaker black can only play A now(see variation).  I can only find this position actually played in pro games when black has this ladder.]
;W[bp]
;B[co]
;W[bo]
;B[do]
;W[br]
;B[dq]
;W[cr]
;B[dn]
;W[mq]
;B[cm]
;W[bn]
;B[po]
;W[dm]
;B[nc]
;W[fc]
;B[be]
;W[ce]LB[bd:A][cd:B]TR[dm]C[Often white plays A or B instead of this move.  However since white has cut at triangle, white should try and develop the right side.  These other joseki's would not be apropriate here aas black would settle on the right side, and the function of triangle would become unclear.]
;B[bd]
;W[bf]
;B[cf]
;W[cg]
;B[df]
(;W[bg]LB[bh:A]C[And here again white chooses to solid connection, instead of the tiger's mouth at A.  This tries for a bit more end game profit on the edge.  See the variation for sequences after the tiger's mouth. However...]
;B[dg]LB[cc:A]C[ White could play at A now to take the corner.  But it is not good.  See the variation.]
(;W[dh]
;B[eh]LB[bh:B][ei:A]C[Park can force here, and Chen cannot double hane at A to expand the right side.  If Chen had a stone at B he could play at A...]
;W[di]C[Now Park needs to look after his corner.]
;B[dc]
;W[cc]
;B[cb]TR[dg][dh][eh][di]C[This move is the second instance of the hane.  It is possible here because again black has the ladder, and also because black has gotten the triangled forcing moves.  If you go back to before these forces you can see a variation if black tries this directly.]
;W[cd]
;B[bc]
;W[db]
;B[ec]LB[bb:A]C[The white move at A does not work well now ( see variation).]
(;W[ed]
;B[eb]LB[fe:A][eg:B]C[Taking the corner at this time is not good for white (see variation).  White might play tiger's mouth at A to defend, and after black secures the corner, white can cut at B to take the 3 stones.  But Chen found a better sequence.]
(;W[eg]C[If black secures the corner now (see variation).]
(;B[ef]C[Black cannot allow white the solid shae they would get by playing here, and so must play this.  However..]
;W[fe]CR[gr]LB[da:A][fg:B][gm:C][iq:F][lr:D][mr:E]TR[ef]C[After  this tiger's mouth black cannot leave the corner any longer. They must take at A.  White then capture the 4 stones with a play at B. We can see that by forcing white to exchange triangle for B white benefited.

We'll leave the game here.  However just one more comment on the solid connection white made at circle.In the end game black made a ponnuki around C.  It wasn't worth so many points in the center as the position was fairly settled then.  However Park followed it up with a invasion at the bottom; white D, black E, then black F, capturing the 3 stones.  This was the winning sequence, and this result is perhaps why all the 2012 games play circle as a tiger's mouth.])
(;B[da]
;W[ef]LB[fe:A]C[.A white stone here is better than a tiger's mouth at A.  White is very solid, black is left with no forcing moves or aji.]))
(;W[bb]
;B[da]
;W[ab]LB[ac:A]TR[bc][bd][be]C[White would like to be able to play this at A to take away one liberty of the triangled stones, helpin in the center, but black would be left with a throw and ko in the corner.  So white would have to play here.  Then...]
;B[fd]
;W[fe]
;B[gd]
;W[ee]
;B[ge]
;W[fg]
;B[gf]
;W[eg]TR[ic][jc][kc][id][jd][kd]C[Black potential in the triangle area is too large, black has a great result from the sacrifice.]))
(;W[bb]
;B[eb]
;W[ca]
;B[ed]
;W[ee]
;B[de]
;W[cb]
;B[fe]TR[ee]C[And now the triangles stone is captured in a ladder.  White needs to add a move in the corner, and black has gotten large potential on the upper side.  White cannot play this way.]))
(;W[cc]
;B[bc]
;W[cb]
;B[ch]
;W[bh]
;B[ci]
;W[bi]
;B[cj]
;W[bj]LB[ck:A]
(;B[cl]LB[bk:A][ck:B]TR[dm])
(;B[ck]LB[cl:A]
;W[cl]
;B[bk]
;W[bb]
;B[em]
;W[dl]
;B[el]TR[bc][bd][be]C[White has to take the triangled stones off the board, so the corner is not large.  Black`s sente and center influence is better.])))
(;W[bh]
;B[dc]
;W[cc]
(;B[cd]LB[cb:A]C[The game move of black A is not working here.  See the variation for why.]
;W[db]
;B[de]
;W[ec]
;B[dg]
;W[dh]
;B[eh]C[You can find this sequence in many games.])
(;B[cb]
;W[cd]
;B[bc]
;W[db]
;B[ec]
;W[bb]
;B[eb]
;W[ca]
;B[ed]
;W[ee]
;B[de]
;W[cb]
;B[ab]LB[ef:A]C[white has a ladder at A.  However even if white did not have this ladder white is ok here.  The continuation is shown as if the ladder was broken.]
;W[ef]
;B[dg]
;W[eg]
;B[dh]
;W[fd]
;B[ba]C[Black can only start the ko]
;W[aa]
;B[ch]C[But this is the best threat black has...]
;W[ac]
;B[bg]TR[eb][dc][ec][ed]C[This is still good for white.  White has sente, a large capture of the triangle stones, and big potential on the upper side.  Black cannot play like this.])))
(;B[bp]
;W[dq]
;B[bq]
;W[cr]
;B[do]LB[co:A]C[white cannot cut at A (see variation).]
(;W[eo]
;B[dn]
;W[ep]
;B[cm]C[Commentary on Baduk TV said there was not yet a professional consensus on this.  Some pro's think white is too thick, while others thought black's position is adequate.  However I cannot find this position in a pro game database, which suggests to me no one actually wants to play it as black.])
(;W[co]
;B[dn]
;W[cm]
;B[br]TR[dp][cq][dq][cr]C[The triangle stones are trapped, white has collapsed])))
(;B[gp]
;W[hq]
;B[fr]
;W[cq]
;B[ep]
;W[eo]
;B[cr]
;W[br]
;B[dq]
;W[cp]C[Black is solid, but white has played on both sides.]))
