Doom

The game is a first person shooter where the player assumes the role of a marine fighting through demonic forces. This follows a failed teleportation experiment by the Union Aerospace Corporation on the Martian moons, which opened a portal to Hell and overran the Phobos base.

Levels are navigated by finding keys for locked doors and activating switches to reach an exit, with the primary obstacle being numerous hostile creatures. The environment design evolves from a futuristic military complex to explicitly hellish settings featuring satanic imagery. The engine supports varied architecture, non orthogonal walls, height differences like stairs, and areas with different lighting conditions.

A selection of weapons is available, each with distinct traits and ammunition types. These range from basic fists and a pistol to a shotgun, chaingun, rocket launcher, plasma rifle, a chainsaw, and the powerful BFG9000. Players can also find items like health packs, armor, backpacks for more ammunition, and special power ups such as temporary invulnerability or berserk strength.

Enemies include corrupted humans and various demons, such as imps and Cacodemons, with particularly strong foes serving as episode bosses. The game popularized multiplayer for the genre, offering cooperative play and a competitive deathmatch mode. Several console ports were released with simplified levels, omitted content, or missing features like the full third episode or multiplayer.