(;
AB[rp][mq][nq][pq][qq][or][qr]
AW[on][pn][qn][rn][mp][np][op][lq][lr][oq][nr][rr][rs][sr]
C[Black plays.
What is the optimal sequence?]
(;
B[ps]
C[Creating eye shape seems hopeful, but ...];
W[ns]
C[... White's descent ruins the eye.]
(;
B[sq];W[os]
C[Black has only one eye after capturing the 3 corner stones.]
)
    (;
    B[os];W[qs];B[pr]
    C[Black dies in gote.

Note that if Black plays A or B, White plays the 1-1 point to make a bulky-5 in the corner.

If Black doesn't play A or B, White can always fill the outside liberties and then capture with A.]
    LB[rq:][sq:]
    )
)
    (;
    B[os]
    C[At least this move forces White to make an inside move.  But, ...];
    W[qs]
    C[... now what?  The situation for Black is similar to the previous variation.];
    B[sq]
    C[Just one example sequence ...];
    W[pr];B[ps];W[ns];B[pr];W[ss];B[so];W[ro]
    C[Black has only one eye.]
    )
    (;
    B[ns]
    TR[mq][nq]
    C[Black can use the aji of the 2 marked stones for a useful forcing atari, but ...];
    W[ms]
    LB[pr:A]
    C[... White's hane tesuji still threatens to make the eye at A false.]
    (;
    B[ps]
    C[Black can start the ko, but now needs an approach move at A for a direct ko.

So Black only has a 2-step ko, which is normally a very bad result.]
    LB[qs:A]
    )
        (;
        B[mr]
        C[Capturing just wastes a ko threat.];
        W[nr]
        )
    )
    (;
    B[ms]
    TR[mq][nq]
    C[Finally!  This placement makes better use the marked stones' aji.]
    (;
    W[mr];B[ns]
    LB[pr:A]
    C[Fantastic move.  Now Black has an extra liberty in the race to make A an eye.];
    W[ls];B[ps];W[os];B[ns];W[ms];B[qs]
    C[Black has a direct ko, which is the best result for both sides.]
    )
        (;
        W[os];B[ps]
        C[Also a direct ko.]
        )
    )
)

