Marine Doom

Marine Doom is a single-level PWAD for Doom II. It was designed for use by the US Marines, but in 1996 was made available for public download by Sergeant Daniel G. Snyder.

In the game, a fireteam, comprising four Marines, is supposed to accomplish a specific mission, the default being the destruction of an enemy bunker, although other scenarios such as a hostage rescue in a foreign embassy can be designed. In order to allow coordination of their movements, these soldiers play on separated computers in the same room. The fireteam consists of a Team Leader, two riflemen, and one machine-gunner.

Marine Doom was later superseded by the completely homebrew game America's Army.

History
In 1995, General Charles C. Krulak, Commandant of the USMC, issued a directive to use wargames for improving "Military Thinking and Decision Making Exercises". He charged the Marine Combat Development Command with the task of developing, exploiting and approving computer-based wargames to train U.S. Marines for "decision making skills, particularly when live training time and opportunities were limited."

A group of simulations experts in the Marine Corps Modeling and Simulation Management Office (based in Quantico, Virginia), including Lieutenant Scott Barnett as the project officer, obtained a commercial copy of Doom and started designing a fireteam simulation, which focused on mutual fire team support, protection of the automatic rifleman, proper sequencing of an attack, ammunition discipline, and succession of command.

Before its completion, their map was modified to work with Doom II v1.9.

Gameplay
The map was designed for four player cooperative mode, and is very difficult in single player mode. The DeHackEd patch provided limits player health to 20, making the player extremely vulnerable to the enemies' hitscan attacks. The pistol is replaced by a rifle with a magazine capacity of 30 bullets (60 with a backpack), the shotgun with a powerful machine gun, and the rocket launcher with grenades (the grenade projectile looks like health potions and is affected by gravity). Sergeants are replaced by enemy riflemen which drop bullet clips and have 40 hit points; but the other enemies are visually unmodified. The chaingunners have been given a strong health boost, boasting 450 hit points.

Things that correspond to vegetation (the burnt tree, twisted tree, and spike stump) have been made shootable and can be used as cover from enemy fire. The tall green marble pillar, however, has been turned into barbed wire fencing.

The shotgun replacement's behavior is a bit glitchy as it will not deselect correctly after having fired. This is because the new animation mixes the shotgun's flash frames (30 and 31) with the normal animation frames (18 to 29). This can be fixed by editing the included SUPER2.DEH file so that frame 22's next frame is 18 (instead of 30) and frame 31's next frame is 1 (instead of 18).