(;
AB[sd][sc][rc][qe][rf][sf][pf][pd][pc][oc][oa][ob]
AW[pb][qb][qc][qd][rd][re][se]
C[Black plays.

Source:
    Go World #16, p. 43, Life and Death]
(;
B[pa]
C[Pushing immediately looks powerful - White seems to have a dead shape.];
W[sb]
C[But White has just enough liberties to save the group.];
B[qa];W[rb]
LB[sc:A][ra:B]
C[A and B are miai for White to live.]
)
    (;
    B[ra]
    C[Hitting the 1-2 point has the same problem for Black.];
    W[rb]
    C[Capturing the 3 stones gives White a couple ways to make 2 eyes.];
    B[sb]
    C[If Black tries something drastic, ...];
    W[sa];B[sc];W[sb]
    C[... White lives with territory.]
    )
    (;
    B[sb]
    C[This goofy-looking move is the best that Black has!];
    W[rb];B[pa];W[sa];B[sc];W[qa];B[sb]
    LB[rc:A]
    C[The name of this result is a "thousand year" ko, because chances are good that neither player will want to start the ko.  To win the ko, one of the players would have to make an approach move first, e.g., at A, which would give the other player an extra move elsewhere on the board.

For example, if White plays A, the ko becomes direct.  Black could capture the corner stone and then only have to ignore one White ko threat to take the entire corner.

If Black captures the corner stone, ignores a White ko threat, and then plays at A to make the ko direct, White will have the option of making 2 free moves elsewhere.

Continue to see what is likely the result of this position.];
    B[ra]
    C[As long as White is careful to keep enough ko threats, the likely result will be that after Black captures here, ...];
    B[sa]
    C[... Black will simply connect to make a seki.

Of course, at a minimum, the original position is still annoying for White, because of the need to keep an adequate supply of ko threats to discourage Black from starting an approach move ko (also called a 2 step ko).]
    )
)

