This is an extremely basic example of how your opponent's best move is often your best move.
(;AB[ra]AB[rb]AB[rc]AB[qd]AB[pd]AB[od]AB[nc]AB[mc]AB[lc]AB[kb]AB[jb]AW[qa]AW[qb]AW[pb]AW[ob]AW[oa]AW[nb]AW[mb]C[Black to kill.]AP[goproblems]
(;B[ma]C[]
(;W[la]C[White is dead and would only play additional moves as ko threats.];B[lb]C[RIGHT];W[na]C[RIGHT])
(;W[lb]C[White is dead and would only play additional moves as ko threats.];B[la]C[RIGHT];W[ka]C[White is still dead in gote.RIGHT]))
(;B[la];W[ma])
(;B[lb];W[ma])
(;B[na];W[ma]))
