HydroGym: A Reinforcement Learning Platform for Fluid Dynamics. - Christian Lagemann; Sajeda Mokbel; Miro Gondrum; Mario Rüttgers; Jared Callaham; Ludger Paehler; Samuel Ahnert; Nicholas Zolman; Kai Lagemann; Nikolaus A. Adams; Matthias Meinke; Wolfgang Schröder 001; et al. (CoRR, 2025)