STRAIN

STRAIN is a 32-level partial conversion for Doom II released in 1997 by the Alpha Dog Alliance. It features nine new or modified monsters through the use of DeHackEd, modified weapons, and a soundtrack written by David "Tolwyn" Shaw, Mark Klem, and Jon Landis. The project had a sporadic development history, exceeding a year due to cyclical interest and disinterest.

Story
STRAIN occurs after the events of Doom II. A military officer in a secret base on the Earth's moon has been engineering demons, creating a new breed of Hellspawn which breaks free of its confines, making an initial landing on Earth. The Doom marine undergoes an experimental treatment to increase his combat potential. Its side effect is that it leaves virtually all of its subjects in a state of perpetual, murderous aggression. The in-game story follows four episodes as the marine fights to an infested spaceship that has landed on Earth, afterward battling his way deep into the heart of the secret installation where the demons originated from.

Levels
First "episode": Second "episode": Third "episode": Final "episode": Secret levels:
 * MAP01: Barracks by Bill McClendon
 * MAP02: Outskirts by Bjorn Hermans
 * MAP03: Downtown by Florian Helmberger
 * MAP04: Industrial Zone by Adam Windsor
 * MAP05: Depot by Jon Landis
 * MAP06: Launch Control by Jon Landis
 * MAP07: En Route by Adelusion
 * MAP08: Hangar by Rich Johnston
 * MAP09: Cargo Bay by Adelusion
 * MAP10: Entryway by Charlie Patterson
 * MAP11: Command Control by Bill McClendon
 * MAP12: Power Station by Bill McClendon
 * MAP13: Ruins by David Rotramel
 * MAP14: Engineering by David Graves, Adelusion, Rich Johnston, and Arthur Chang
 * MAP15: Subsidiary Power by Chainsaw
 * MAP16: Living Quarters by Charlie Patterson and Eric Roberts
 * MAP17: Promenade by Holger Nathrath and Arthur Chang
 * MAP18: Relay Station by David Rotramel
 * MAP19: Waste Processing by Darrell Esau
 * MAP20: Reactor by David Davidson
 * MAP21: Maintenance by Adelusion and Arthur Chang
 * MAP22: Specimen Storage by Adelusion
 * MAP23: Dispensary Alpha by Adelusion
 * MAP24: Sub-Laboratory by Adelusion
 * MAP25: Main Laboratory by Arthur Chang
 * MAP26: Main Laboratory II by Holger Nathrath, Charlie Patterson, and Eric Roberts
 * MAP27: Dispensary Beta by Andy Badorek
 * MAP28: Unknown by Bjorn Hermans
 * MAP29: Self-Destruct by Ron Allen
 * MAP30: Boss by Jon Landis and Rich Johnston
 * MAP31: Secret by Jon Landis
 * MAP32: Super-Secret by Holger Nathrath and Adelusion

Weapons
STRAIN modifies the original Doom weapons as follows. STRAIN makes several other core gameplay changes.
 * The marine punches quickly with both fists in succession. Both swings are boosted by the berserk powerup.
 * Pistol fires faster.
 * Shotgun has new graphics and fires faster.
 * NFG replaces the plasma rifle. Its base damage is seven points higher.
 * Psychic Blaster replaces the BFG9000. It consumes three rockets per shot, launching partially invisible projectiles at a faster rate that only cause blast damage.


 * Players begin with no ammo at pistol start.
 * Cells are capped at 50 (100 with the backpack).
 * Megaarmor sprite is replaced and increases armor to 300 percent.

Monsters
STRAIN features a number of new monsters. The most basic monsters (zombieman, shotgun guy and imp) appear unchanged, as does the arch-vile. Cacodemons, hell knights and barons of hell fire faster projectiles. The commandos have new sprites but are otherwise unchanged.


 * Strain Imps replace arachnotrons. They appear identical to an imp with a higher-pitched alert noise. These move incredibly fast and have slightly more hit points. Attacks begin with a brief pause, after which they throw fireballs at a steady pace.
 * Strain Demons replace demons and are recolored to bright red. Strain demons are significantly more durable than regular ones.
 * Holo-bots replace revenants. They move very slowly and fire both types of revenant missiles, which travel at a much slower pace. Holo-bots also appear in a partially invisible variety.
 * Dopplegangers replace lost souls. The two monster types are similar in appearance but Dopplegangers are brightly colored. They attack with a fireball before charging.
 * Ministers of Pain are miniature cyberdemons. They fire normal rockets but are vulnerable to blast damage.
 * Polydrones are flying cubes that resemble spawn cubes. They attack with the spiderdemon's chain shotgun. Their corpses are fiery wrecks that damage the player at close proximity.
 * Demon Lords replace mancubi. They are recolored barons / hell knights and are much tougher, being the most durable monsters in STRAIN. They attack in several barrages of five green plasma attacks.
 * BFG Troopers look identical to zombiemen. They attack with BFG blasts.
 * "Vacuum Demon" is an unused monster that replaces the SS Trooper. It is invisible, incredibly small and fast, and can kill the player in god mode. The STRAIN team made it to simulate death due to exposure to the vacuum of space in certain sections of the story's moonbase but did not implement it in the final product.

Other notes

 * MAP07: En Route is impossible to complete in ports based on old versions (prior to 2.3.0) of ZDoom, as the level relies on the occurrence of a spechits overflow in order for the exit to work. Recent versions of ZDoom identify the map and automatically apply the required compatibility flag. There are also problems with the DeHackEd patch when it is used with Doom Legacy. Doom Wad Station provides a fixed version at their STRAIN Page.


 * MAP09 originally appeared as MAP04 of Dystopia 3.
 * MAP23 originally appeared as MAP10 of Dystopia 3.


 * Holger Nathrath's levels were likely donated outtakes from the cancelled Serenity IV project, according to Sam Woodman's notes in . Nathrath attempted to donate such maps to the Eternity TC and Sam Woodman's megawad, Testament of Judgement.

Additionally, MAP17, MAP18, MAP22, and MAP24 share a room giving a sense of partial continuity.