(;
AB[mn][nn][oo][po][qo][ro][mp][np][op][rp][mq]
AW[ll][nm][om][pm][qm][rm][kn][ko][pp][qp][kq][lq][nq][oq][rq][mr]
C[Black plays.]
(;
B[pq]
C[One obvious 1st choice, but ...];
W[qq];B[pr];W[or]
(;
B[os];W[nr];B[qr];W[rr]
C[... Black has nothing.]
)
    (;
    B[ps]
    C[Another common tsumego theme, but ...];
    W[qr]
    C[... Black is still short a liberty.]
    )
)
    (;
    B[rr]
    C[Does the attachment work?];
    W[qr];B[sq];W[qq]
    (;
    B[pr];W[pq];B[qs];W[nr]
    C[Black has nothing but false eyes in the corner.]
    )
        (;
        B[nr];W[or]
        C[Black still has only one eye.]
        )
    )
    (;
    B[qr]
    C[The placement often causes trouble, but ...];
    W[qq];B[rr];W[sq];B[pr];W[pq]
    C[... White can defend with simple moves.]
    )
    (;
    B[nr]
    C[Correct.];
    W[or];B[qq];W[pq];B[qr];W[rr];B[rs];W[pr];B[qs]
    C[White has a liberty shortage.  Black makes a 2nd eye in the corner.]
    )
    (;
    B[qq]
    C[This result of this atari is left as an exercise for the reader.]
    )
)

