The Doom Engine was written in Watcom C by John Carmack, John Romero and Dave Taylor. It runs on DOS and is capable of generating 256 colour graphics. The game will run well on any machine above a 486, and it requires 8 MB of RAM.
In Doom the player finds himself on a lost moon base on Mars, infested with monsters from another dimension. The game is divided into a number of areas, called levels, which a player must complete. Each level consists of a number of structures such as rooms, large open areas, tunnels, dark and bright areas, etc., and there are various objects in the level that the player can interact with. There are enemies to shoot, weapons and other items that the player can pick up.
Let us then look at what the Doom engine must handle -
Although Doom looks three-dimensional, the representation of the level is two-dimensional. No object can ever be on top of any other object. However, rooms, and other areas can have different floor and ceiling heights, giving the impression of being in a 3D world.