Evolution of median DM (left bottom panel) and gas (right bottom panel) density of the environment around dark and bright galaxies. Dark galaxies are shown as dotted-dashed lines, and bright galaxies as solid lines. Each colour represents a different simulation, blue shades for HESTIA and red for NIVARIA-LG. The shaded and striped backgrounds are the regions limited by the 16^th and 84^th percentiles of the distributions. The environment is defined as a spherical shell between 1 R_vir and 7 R_vir of each halo at each time. The evolution of the median R_vir of all dark and bright galaxies is shown in the top panels as a solid black line, along with the 16^th and 84^th percentiles as a shaded region.