(;GM[1]FF[4]CA[UTF-8]AP[CGoban:3]ST[2]
RU[Japanese]SZ[19]KM[0.00]
C[some endgames you don't know]
(;AW[ic][bd][cd][dd][de][he][ef][ff]AB[be][ce][cg][dg][eg][fg][gg][dj][cl]
;W[ae]C[How will black answer after this white's endgame?]
(;B[af]C[not good answer, right?]
;W[bf]
;B[ad]
;W[cf]
;B[ae]
;W[ag])
(;B[bf]C[almost everyone will answer this way])
(;B[ag]C[someone who studied the endgame book might answer this move ])
(;B[bg]C[this answer lost some point]
;W[ag])
(;
;B[af]C[this is the correct answer]
(;W[ad]C[if white connects, black makes one more point]
;B[cf]C[this is the correct sequence for both])
(;W[bf]C[why can't white cut?]
;B[ad]
;W[cf]
;B[bg]
;W[ae]
;B[be]C[now there are two ways to play for white 

If white does not have enough ko threats, he has to extend.]
(;W[ac]C[if white has more ko threats, white will block.]
;B[ae]
;W[ce]
;B[ag]
;W[bc]
;B[ag]TR[bf][ag][bg]SQ[ac][bc]C[Let's compare this to the previous variation. 

black lost 3 points.
white lost 2 points.
white gained one point, but in gote.])
(;W[bc]
;B[ac]
;W[ab]
;B[ae]
;W[ce]
;B[ag]
;W[bb]
;B[ag]TR[bf][ag][bg]SQ[ab][bb][ac][bc]C[Here black lost 3 points again.
However, white lost 4 points now.

So, white actually lost 1 point in the exchange and on top of that, white also lost sente!]))))
(;AW[ib][nb][pb][jc][lc][oc][pc][ld]AB[nc][qc][nd][od][pd][rd][qe][qg]C[endgame, black's turn]
(;B[qb]
;W[oa]
;B[qa]
;W[pa]
;B[mc]
;W[mb]LB[la:2][ma:3][na:4][lb:1][ob:5]C[not good

white has 5 points])
(;B[mb]
;W[mc]
(;B[na]C[A mistake]
;W[ob]
;B[qb]
;W[lb]
;B[pa]
;W[ma]C[same as before,  not enough]
;B[qa]
;W[oa]LB[la:1][na:3][mb:2]C[white has 3 point + 2 captured stones = 5 points])
(;B[oa]C[the correct move]
(;W[ob]C[good move.]
;B[qb]
;W[lb]
;B[pa]
;W[ma]C[good endgame]
;B[qa]
;W[na]LB[la:2][mb:1]C[white has 3 point (2 points + 1 capture)

black destroyed 2 points more])
(;W[ma]
(;B[qb]C[same]
;W[ob]
;B[pa]
;W[lb])
(;B[ob]C[big mistake]
;W[pa])))))
(;B[dp]
;AE[dp]AB[pd]
;W[qf]
(;B[nc]
;W[pj]
;B[jd]C[Later, in middle game a joseki can be played.]
;W[qc]
;B[qd]
;W[rd]
;B[pc]
;W[rb]
;B[qb]
;W[rc]C[In this position, let's think about endgame.


(later) The normal move is big, but gote. When you want to keep sente in endgame, white can play here!]
(;W[pb]C[This is the normal move, it is biggest in this corner.

To calculate its exact value is difficult, but this is worth more than 6 points.]
;B[ob]
;W[qa]LB[nc:A]C[However, white has gote. He has no good follow-up.

Note that this is because of the stone at A. If this stone would be high, the situation would be different.])
(;W[qa]C[Tesuji!



If black doesn't respond..]
(;B[pb]
;W[pa]
;B[oa]
;W[ra]
;B[ob]C[Comparing this to the variation where white captured the stone.. (laat zien) white has 3 points less in the corner. But...white keeps sente, which is huge!

See bonus sgf file for an amazing pro that played like this.])
(;B[dp]
(;W[pb]C[White will not play here. This returns to the normal way.]
;B[ob])
(;W[oa]C[White will play here. This is huge.]))))
(;B[nd]
;W[pj]
;B[jc]
;W[qc]
;B[qd]
;W[rd]
;B[pc]
;W[rb]
;B[qb]
;W[rc]
;W[pb]LB[nd:A]C[Endgame again. Since A is now high, this white move is bigger than before.]
;B[ob]
;W[qa]LB[oa:A]C[After this, white has big endgame sente at A. ]
;B[dp]
;W[oa]C[We can expect this.]
;B[nb]
;W[na]
;B[ma]
;W[pa]
;B[mb])))
