We consider classical dynamics of a one-dimensional system of N particles bouncing on an oscillating mirror in the presence of gravitational field. The particles behave like hard balls and they are resonantly driven by the mirror. We identify the manifolds the particles move on and derive the effective secular Hamiltonian for resonant motion of the particles. https://www.ealisboa.com/quick-offer-NEW-LED-Illumivein-Vein-Finder-Transilluminator-to-Find-Veins-for-Phlebotomy-and-IV-must-buy/