The ordered phases formed by polymeric nanocolloidal particles with a core-shell architecture are typically very different from those seen in classical hard colloids. The differences must invariably be related to softness of particles. Here we discuss the T=0 phase diagram of a 2D model of core-softened particles represented by the hard-core/square-shoulder pair potential. The aim of the analysis is to show that a simple generalization of the hard-core potential is sufficient to induce several rather complex crystalline and quasicrystalline phases, and to illustrate how these structures can be systematically constructed and compared using a geometric scheme based on canonical local packings of the particles.