A later remaster that added the "shoulder-mounted flashlight," improved performance for consoles, and included the Resurrection of Evil expansion. Console Commands & Cheats
Players can access the developer console by pressing Ctrl + Alt + ~ to enter commands like: god : Invincibility. give all : All weapons and maximum ammo. noclip : Walk through walls.
id Software (the first time they used C++ instead of C).
Heavy emphasis on darkness and shadow. The original game famously required players to toggle between their weapon and a handheld flashlight.