Classical Plucker formula related the degrees and topology for dual curves in dual projective planes. It can be generalized to arbitrary dual varieties after viewing these from the perspective of intersection theory of complex Lagrangian subvarieties in holomorphic symplectic manifolds under Mukai flop. In joint work with Jiang and Xie, we lift this formula to the categorical level, which is related to works of Homological Projective Duality by Kuznetsov and others.