High definition Cubemapped Skyboxes for Doom 1, Created with Space Engine, as static, unique "astronomically correct" skybox overrides for the base doom skies for the first 3 episodes. This mod also includes an optional series of skyboxes for all 9 maps of Episode 1, showing Phobos as it progresses along its orbit around Mars, entering the planet's shadow the last 3 maps (e1m6 to e1m8). Disabled by default, there is instead a static Phobos sky showing Mars and Valles Marineris. This mod includes a static override for Brutal Doom 21, which unfortunately means you won't experience the changing skies. It works properly in older versions of Brutal Doom and in Project Brutality.