(;GM[1]FF[4]CA[UTF-8]AP[CGoban:3]ST[2]
RU[Japanese]SZ[19]KM[0.00]
PW[baduk]PB[movies]AB[pd][qg]C[Today we would like to continue the san-san series by showing you the ins and outs of a corner group that comes forth from the last variation we showed in episode 12. 
]
;W[qc]C[Black has an oogeima stretching from his hoshi stone and white invades on 3-3..]
;B[pc]
;W[qd]
;B[qe]
;W[re]
;B[rf]
;W[pe]
;B[qf]
;W[pb]
;B[ob]
;W[qb]
;B[nc]LB[rd:B][sd:A]C[At this moment white has two options to defend his corner. A or B]
(;W[rd]C[This is the normal move, which is played most often by professionals. It is usually best for endgame.]
(;B[oe]CR[oe]LB[oa:A][pa:C][se:B]C[The white group is alive. It is one of the most basic corner groups you will encounter in your go games, and it occurs frequently.
A, B and C are all sente for black.]
(;AE[ob][pb][qb][nc][pc][qc][qd][rd][oe][pe][qe][re][qf][rf]AW[hb][ib][kc][lc][hd][id][jd]AB[gb][jb][dc][gc][jc][de]C[In certain special situations the hanging connection, or tigersmouth, is best. This is one of them.]
;W[qc]
;B[pc]
;W[qd]
;B[qe]
;W[re]
;B[rf]
;W[pe]
;B[qf]
;W[pb]
;B[ob]
;W[qb]
;B[nc]LB[sd:A]C[Here the hanging connection at A is correct ]
(;W[rd]C[If white would play the usual move, it would actually be a mistake here!]
;B[oe]
;W[cq]
;B[oa]LB[jb:B][jc:A]C[This black descent is the keypoint of the situation. It is sente against the L+2 group and it also threatens to set blacks 2 seemingly captured stones in motion.]
(;W[rb]C[If white defends his corner..]
;B[ka]C[Black has a very sneaky sneaky tesuji up his sleeve!]
;W[mb]
;B[ma]C[Black connects all his stones and suddenly whites group becomes weak. A great result for black!])
(;W[mb]
;B[rb]C[Black has aji in the corner and can make a ko.]
;W[ra]
(;B[sb]C[In such a tsumego situation the first move that comes to mind is the black extension. However, this doesn't work here.]
;W[sc]LB[pa:A][se:B]C[White has one eye in the corner and A and B are miai : 2 eyes in total. ])
(;B[sc]C[The correct move. ]
(;W[rc]C[If White tries to kill the black stones, he actually dies himself. ]
;B[sb]
;W[pa]
;B[se]C[White is confronted with a lack of liberties and can't seperate the black stones. ])
(;W[pa]C[This leads to a ko.]
;B[sa]C[White can take the ko first. But still this is a big success for black. What a master player.]))))
(;W[sd]LB[oa:A]C[The correct move. In this shape, Black A is not sente anymore. ]
;B[ka]C[Now this fails. ]
;W[mb]
;B[ma]
;W[na]C[White can seperate.]))
(;CR[qb][qc][qd][rd]SQ[pb][re]C[This is called the L + 2, since the shape resembles the letter L which has one extra stone on both sides (the marked square stones). ])
(;B[se]C[When black plays one of the two hanes]
;W[sb]C[You can defend your corner with a stylish jump.])
(;B[pa]C[Here the stylish jump also works, but...
]
;W[rb]C[This is the clearest shape in this position. ]))
(;B[oa]C[The descent is sente for black.]))
(;W[sd]LB[oa:A]C[This move is usually wrong, because of a black endgame tesuji.]
(;B[sf]C[First lets point out that this descent is sente. White has to respond to this move or else his group will die.]
(;W[dd]
;B[rd]C[Black kills. This move is cool to remember. ]
;W[rc]
;B[sb]C[Another tesuji!]
;W[se]C[White can't make an eye here: black will simply atari. ]
;B[sc]
;W[rd]C[White has only one eye.])
(;W[sb]SQ[qa][ra][sa][rb][rc][sc]C[The proper response. White lives. Let's focus on endgame counting. Whote has 6 points in the corner (the marked spots). It is not sure that point number 6 will actually be whites territory, but lets count it for the sake of comparison. ]))
(;B[sb]C[In the late stages of endgame black can use this vital point to take away some territory of white.]
;W[sc]
;B[sf]
;W[rb]
;B[rd]
(;W[sa]
;B[se]SQ[qa][ra][sb]C[White has 3 points of territory and sente. Black and white both captured one stone: this is even so we leave this out.])
(;W[rc]C[Why not take the black stone instead? Isn't that more points? Yes, it's 1.5 points bigger, but it also loses sente. ]
;B[se]
;W[sa]C[White has captured two black stones and has 3 points of territory, making 5 in total. Black has the possibility of taking the ko, so we count this as minus half a point for white. Giving him 4.5 points. In the previous variation white had 3 points and sente. Black has sente now. To summarize white can choose to take sente or to take 1.5 points in gote.]))))