(;
AB[sr][rq][rp][qp][pp][op][np][mp][lp][lq][lr][jr]
AW[ls][mr][mq][oq][nq][pq][qq][qr][rr]
C[Black plays.

A very simple, but highly instructive position.]
(;
B[or]
C[The first instinct might be to attack White's eye-shape here.];
W[rs]
(;
B[ns]
C[Black seems to have an easy kill, but ...];
W[ps];B[ms];W[os]
C[... White catches the edge stones in a liberty shortage to make the 2nd eye.]
)
    (;
    B[ps]
    C[Better than the previous variation, but ...];
    W[ns]
    LB[pr:A][os:B]
    C[... White has this shape move for seki.  A and B are miai for White.]
    )
)
    (;
    B[ps]
    C[Not a good point for attacking White's eye-shape.];
    W[or]
    C[For example, White can make a standard seki shape.];
    B[ns];W[ms];B[os]
    C[White lives.]
    )
    (;
    B[ns]
    C[The only move!]
    (;
    W[ms];B[or];W[rs]
    C[White desperately tries to expand the eye-space, but ...];
    B[ps]
    LB[pr:A][nr:B]
    C[... Black makes a classic dead shape.  White cannot approach the 3 stones without Black forming a bulky 5.  And to remove the White stones, Black can fill the outside liberties, and then play A, followed by B to give atari.]
    )
        (;
        W[os]
        C[The trickiest defense.]
        (;
        B[or]
        C[The mistake White is hoping for.];
        W[ps]
        C[Now White lives.]
        (;
        B[ms];W[rs];B[ks];W[nr]
        )
            (;
            B[rs];W[nr]
            )
        )
            (;
            B[ps]
            C[Correct.];
            W[or];B[ms]
            )
        )
    )
)

