(;
AB[oq][pq][qq][mr][ms][rr][rs][sr][ss]
AW[mp][np][op][pp][qp][rp][lq][lr][ls][rq][sq]
C[Black plays.]
(;
B[os]
C[Looks like correct shape, but fails here.];
W[nr];B[nq];W[qr];B[pr];W[qs]
)
    (;
    B[ps]
    C[Correct shape, but how does Black handle the weaknesses to the left and right?]
    (;
    W[qr]
    C[For example ...];
    B[nr];W[pr];B[or];W[qs];B[rr]
    C[... but Black has this "under the stones" tesuji.];
    W[os];B[rs];W[ps];B[ns];W[ps];B[sr]
    C[Black hangs on by a thread to make a 2nd eye.]
    )
        (;
        W[nr]
        C[And if White starts on the other side, ...];
        B[nq]
        C[... Black can block here.  The reader can explore the following variations.]
        (;
        W[qr];B[ns];W[or];B[pr];W[qs];B[rr]
        )
            (;
            W[mq];B[or];W[qr];B[ns]
            )
            (;
            W[or];B[mq];W[qr];B[pr];W[qs];B[rr]
            )
        )
    )
)

