DYNA (or "Dynamic x-ray reflectivity (off-or-on resonance regime for isotropic, anisotropic and magnetic multilayers) simulation program") is a simulation tool to analyze structural, magnetic and electronic profiles along the growth direction of ultrathin layers. It simulates conventional x-ray or optical reflectivity, resonant (or "anomalous") x-ray reflectivity, "orbital reflectometry", magnetic resonant x-ray reflectivity with applications to magnetic or anisotropic layers, in hard or soft matter. Dyna is an on-going open-source project, that uses Matlab environment, the move to Python + Qt being in progress.