Page "Doom (video game)" Paragraph 6

As the last man standing, the player character's mission is to fight through the entire onslaught of demonic enemies by himself in order to keep them from attacking Earth.

In order for the game to be completed, the marine must fight through Phobos, Deimos, and then Hell itself, each presented as an episode containing eight distinct levels, along with an optional ninth hidden level for each one.

Knee-Deep in the Dead, the first episode and the only one in the shareware version, is set in the high-tech military bases, power plants, computer centers and geological anomalies on Phobos.

It ends with the player character entering the teleporter leading to Deimos, ending with him getting overwhelmed by monsters, if not killed.

In the second episode, the Shores of Hell, the character journeys through the installations on Deimos, areas of which are interwoven with beastly architecture, warped and distorted by the hellish invasion.

After defeating the titanic Cyberdemon, he discovers the truth about the vanished moon: it is floating above Hell.

After climbing down to the surface, the third episode, called Inferno, begins.

After the huge Spiderdemon that masterminded the invasion is destroyed in the final mission, a hidden doorway back to Earth opens for the hero, who has " proven too tough to be contained ".

In the game's final cutscene, the camera pans over a verdant field complete with flowers and bunny rabbits, only to reveal a burning city and a bunny's head impaled on a stake: the demons have invaded Earth, paving the way for Doom II: Hell on Earth.