Doom Delta

Doom Delta is a gameplay mod for GZDoom created by DrPyspy first released in 2016. It incorporates elements from prerelease iterations of Doom such as the alphas and the Doom Bible, such as multiple playable characters, the helmet hud, a scoring system, the early version of the BFG9000, and the scrapped dark claw and Unmaker weapons.

Doom Delta was the winner of a gameplay mod award at the Cacowards 2017, alongside Final Doomer and High Noon Drifter.

Player classes
All the player characters are based off the original character designs found in the Doom Bible, with some artistic liberty taken:
 * Lorelei Chen: Lorelei is the fastest of the four characters in more ways than one! Her base speed is remarkably quick (sacrificing most of her sprint ability), and has an increased fire rate on most weapons (excluding power weapons).
 * John Pietrovich: John is an all-around type of character. Out of all available characters, he is the most balanced in all fields. Normal firing speed, takes normal damage, has normal speed. He is the closest to the vanilla Doom Marine out of all four characters.
 * Dimitri Paramo: Dimitri is a tank. He can soak up direct and explosive damage like nothing, but is fairly slow compared to the others. His sprint slowly loses speed, requiring a brief break before he can reach top speed again.
 * Thi Barret - Thi is a glass cannon. She moves quickly and is able to duck in and out of encounters with ease. However, due to her extra vulnerability to damage, she can be overwhelmed faster than the other classes.

Weapons
The arsenal is largely based off the one from the Doom alphas and the press-release beta, with some weapons from the Doom bible also making an appearance:
 * Rifle: Replacing both the pistol and the first, the rifle is the standard-issue weapon and has a bayonet attachment for melee combat and when running out of ammo.
 * Shotgun: Similar in appearance to the Doom alpha one, with identical behavior as the final version.
 * Super shotgun: Based off the unfinished sprites during Doom 2's development cycle, but with a reload animation similar to the final version.
 * Machinegun: Based off the Doom alpha weapon of the same name, the machinegun is the standard chaingun replacement and fires bullets in quick succession.
 * Chaingun: A rarer spawn compared to the machinegun, the chaingun initially fires slowly but after it has built its momentum it will deliver a devastating hail of bullets against any opponent.
 * Rocket launcher: The same as the final version.
 * Plasma rifle: Using the bulkier design found in the press-release beta, it fires alternating green and red plasma shots.
 * Dark claw: Based off the cut weapon from the Doom bible, this severed demon arm fires blue projectiles which can rip through multiple targets. It runs on human souls, obtained by killing zombies, and is a rarer spawn compared to the plasma rifle.
 * BFG 2704: The strongest tech weapon in the game, the BFG is based off the press-release beta version, firing multiple red and green plasma balls in rapid succession, easily able to kill even groups of barons almost instantly.
 * Unmaker: Based off the Doom bible weapon and quite different from the weapon that would later be baptized with this name from Doom 64, the Unmaker fires four souls out of its demonic head, seeking out and tearing through demons. Runs on human souls like the dark claw, and is a rarer spawn compared to the BFG 2704.

Monster changes
Many of the enemies in the game have been modified to more closely resemble their Doom beta incarnations. For instance, the imp and baron now fire the projectiles they used to in the press-release version of Doom. The lost soul is also (optionally) back to its alpha state of having an entirely different sprite-set and firing a hitscan attack. Two new enemies also appear, the blob, based off an unreleased set of sprites, and the gargoyle, a low-tier flying enemy similar to an imp that was mentioned in the Doom bible.

Configuration and other changes
One important aspect of Doom Delta is its amount of options and configuration, allowing the end-user to modify many aspects of the mod. For instance, some enemies can have their sprites changed (such as the zombies having helmeted and non-helmeted variants), others can have different behavior (the lost soul can behave as in the alpha, as in retail, or in an entirely new manner exclusive to Doom Delta), as well as other changes to the interface, like being able to select between the 0.3, 0.4 and 0.5 HUDs or having alpha/beta skies, or even the ability to remove the player classes altogether and play with the singular Doom marine from retail.