Doom ROM

Doom is a first-person shooter presented with early 3D graphics. The player controls an unnamed space marine—later termed “Doomguy”—through a series of levels set in military bases on the moons of Mars and in hell. To finish a level, the player must traverse through the often labyrinthine area to reach a marked exit room. Levels are grouped together into named episodes, with the final level focusing on a boss fight with a particularly difficult enemy. While the environment is presented in a 3D perspective, the enemies and objects are instead 2D sprites presented from several preset viewing angles, a technique sometimes referred to as 2.5D graphics or billboarding.

Doom is divided into three episodes: “Knee-Deep in the Dead”, “The Shores of Hell”, and “Inferno”. A fourth episode, “Thy Flesh Consumed”, was added in an expanded version of the game, The Ultimate Doom, released on April 30, 1995, two years after Doom and one year after Doom II. The campaign contains very few plot elements, with the minimal story instead given in the instruction manual and in short text segues between episodes.

In the future, an unnamed marine (known as the “Doom marine” or “Doom guy”) is posted to a dead-end assignment on Mars after assaulting a superior officer who ordered his unit to fire on civilians. The Union Aerospace Corporation, which operates radioactive waste facilities there, allows the military to conduct secret teleportation experiments that go terribly wrong. A base on Phobos urgently requests military support, while Deimos disappears entirely, and the marine joins a combat force to secure Phobos. He waits at the perimeter as ordered while the entire assault team is wiped out. With no way off the moon, and armed with only a pistol, he enters the base intent on revenge.