“…At the other extreme, for compact billiard tables and smooth bounded potentials, mechanical HISs limit, at high energy, to the corresponding billiard flow. The theory for intermediate energy values includes local analysis near periodic orbits [5] and near smooth convex boundaries [2,25], and, for some specific classes of HIS, hyperbolic behavior [12,[20][21][22], Liouville integrable [3,6,11,16,17] and near-integrable [15] dynamics were established. A class of quasi-integrable HISs, related to the quasi-integrable dynamics in families of polygonal right-angled corners, was introduced in [1].…”