You'd be forgiven for playing Brutal Doom for the first time and coming away with the impression that you just played the most gratuitous, over-the-top violent video game ever made. Trailers announcing new versions of the mod, first published in 2010, drive this impression home. Firing a BFG blast into a horde of Imps triggers an explosion of blood that makes Johnny Depp's death scene in A Nightmare on Elm Street look tame.

Wipe away all the mutilated limbs and buckets of blood, and Brutal Doom has a lot more to offer. Its feature set is so thorough, its changes so sweeping and evolutionary, that John Romero said back in 2013 that id "would've destroyed the game industry" had id Software released it instead of the original Doom back in the early 1990s.

As a Brutal Doom buff, I was excited to catch up with the mod's creator, Marcos "Sergeant Mark IV" Abenante. The Sarge was kind enough to dissect some of the game's changes both huge and nuanced, explain how Brutal Doom caters to equally players who prefer a moodier, slower pace, as well as those who revel in sending demons back to hell in doggy bags, and share his thoughts on his mod's excessive violence stealing the spotlight from its more impressive features.

What led to your interest in designing Doom mods?

Making mods for Doom was a childhood dream. I wanted to make "my own Doom" since I played it the first time on my Sega Saturn back in the late '90s. Around 2009 when I played Doom mods for the first time I got instantly hooked by the great customization capabilities of the engine and how easy was to mod it.

Brutal Doom is one of the most expansive mods ever created. Among other features, you overhauled the game's arsenal, gave enemies new attacks, changed or replaced power-ups, and painted levels in blood. How did the mod start? Did you think of one feature that snowballed, or did you have an all-or-nothing mindset from the beginning?

A year before, I made a mod called ArmageDoom (yeah, silly name) which contained new maps, monsters, a new plot, and a lot of stuff, but it proved to be way too ambitious for a first time mod. It was a mess of unfinished features. There were others gameplay mods at that time that tried to overhaul Doom such as Beautiful Doom and Polished Skull, but none of them satisfied me, so I decided to make a new simpler and smaller mod to improve my intimacy with the engine. I wanted to make a mod that would make the regular game look, sound, and play the way [that left me] completely satisfied, then transfer these systems to a bigger mod.

The initial concept of Brutal Doom was just a mod to test a headshot system, and a unified blood and gibs system with some basic physics. People loved it right when the first version came out, there were several people hosting servers on day one. So I kept adding more and more stuff.

Turns out that the visual effects of Brutal Doom are way too detailed to fit my initial vision of ArmageDoom. I didn't design Brutal Doom expecting people to use it on maps that puts more than 30 or 40 enemies on the screen at the same time, so I could go overboard with the gibs and particles. On ArmageDoom you would often fight 200 or 300 enemies, with like 30 friendly marines at your back in battles that would look like something out of Starship Troopers or Warhammer 40k. So if I had to restart working on that mod, I would need to go back and start a whole new gore system from scratch.

Was there a particular reason you targeted the classic Doom games as opposed to 2004's Doom 3?

I got a bit disappointed with Doom 3. It was a cool game, but definitely not a cool Doom game. So I started to add to Classic Doom all the stuff I wanted to see in Doom 3.

Classic Doom provides arguably the most well-rounded arsenal in FPS games. How did you approach tweaking weapons that had been balanced for over two decades?

The original game had a progressive weapon policy. You get the chaingun, which is basically a pistol that fires faster and can snipe things with two shots at once. You get the super shotgun, which fires more pellets per shell than the regular shotty, and makes the regular shotty only useful if you are out of chaingun ammo.

For BD, I have a policy that no guns should be deemed deprecated when you get a bigger gun. Every gun has an unique characteristic with its advantages and disadvantages.

The assault rifle, which replaces the pistol, exemplifies that point. John Romero explained how, speaking to your example, the pistol is still useful after you get the chaingun because it's good for chipping away at monsters. Drawing from my own experience, though, I rarely used weapons below the shotgun. That wasn't the case with the assault rifle; I use it frequently, even on later levels.

Yes, the rifle still remains the most useful weapon for dealing with zombies even after you find the rest of the arsenal. Some custom maps pits you against strong opponents with just your starting loadout and a shotgun, so the rifle is designed in a way that a competent player can use it to quickly kill a Mancubus or even a Baron of Hell. The weapon is balanced with its need to reload and reduced accuracy when firing on full-auto.

Doom's pistol and chaingun did the same amount of damage. The only difference was their rates of fire. How did you want to differentiate the AR and chaingun?

On BD. each bullet fired from the rifle deals 20 percent more damage than the bullets fired by the chaingun. The rifle has a longer barrel, and a gun with a longer barrel makes the projectile spin faster before coming out, reaching a higher muzzle velocity even if it's firing the same type of ammunition. This added to a great accuracy: two degrees spread when firing from the hip, one degree when firing while aiming down the sights, no spread when firing on semi-auto in both ways, against 4 degrees of spread on the chaingun. And it makes it extremely effective against zombies on close quarters, and imps and lost souls on long distances.

A rifle becomes pretty useless against a group of Pinky demons because it lacks the fire rate to slow them down; they will easily corner you with their speed boost and bite you while you are reloading. The chaingun lost its sniping capabilities of the original game—but still fires more accurately when on full auto—and performs better against large groups of enemies due its higher fire rate and its lack of need to reload, and is the only weapon that can stunlock flying enemies. This is important in BD, as flying enemies have the ability to quickly circle-strafe the player when they get out of their pain states. 

Due its wind-up time, the chaingun becomes a bad weapon of choice for clearing out corridors with confrontations far from each other. A zombie will mostly fire at you, or an imp will leap at you before your gun even starts firing and walking around with the barrels rotating will make noise and ruin any potential ambush chances you could get.

Brutal Doom's assault rifle proves handy even late into any classic Doom game.

Doom's shotgun is almost perfect. It strikes a comfortable ratio of power to speed, and is useful at short, medium, and long ranges. Given all that, did you see any room for refinement, or perhaps modernization?

Doom 2 introduced the super shotgun, which made the original shotgun completely obsolete. The original shotgun fires seven pellets while the super shotgun fires 20 pellets—it magically fires three more pellets per shell—with the double horizontal spread, and an added 7.1 degrees vertical spread while the original shotgun has zero vertical spread.

The Super Shotgun not only deals more damage per shell, but also fires them faster. The original shotgun fire has a 37-frame cooldown before each shot—the game logic runs at 35 fps, so it's roughly one second—while the Super Shotgun's fire animation takes 57 frames. That makes 28.5 frames for each shell. So the super shotgun doesn't just fire three pellets more per shell, but also fires them faster, and the double spread is not enough to compensate that.

My solution to rebalance them was to enforce the shotgun's original purpose over the addition of the super shotgun. It's a common mistake in video games to make shotguns inaccurate over long distances, when in real life, a buckshot can effectively put down a deer 50 meters away, and probably take down a human at much longer distances. There was a limitation in the original game's engine that made all guns have the same spread pattern—5.6 degrees to the sides, no vertical spread—so id Software accidentally made one of the most realistic shotguns in history of videogames.

Some mods attempt to balance the shotguns by nerfing the super shotgun and making it fire 14 pellets. Instead, I buffed the shotgun to fire 10 pellets. The shotgun is made even more accurate by reducing its spread pattern from 5.2 degrees to 2.7 degrees. now both horizontally and vertically. Now the shotgun is powerful enough to kill lost souls with a single shot, which is very satisfying, and most of times kill Pinky demons with two shots; it takes 3 shots on the original game.

Out of all the bullet-based weapons, it can deliver the highest amount of stopping power at the longest range possible, and it can take down a room full of imps much safer than with a super shotgun: It is guaranteed to kill them with one shot before they can leap at you and you don't have to deal with the inconvenience of having to reload after each shot, leaving you vulnerable to the other enemies in the room.

'Brutal Doom Marine was here.'

What weapon was the most difficult to modify?

The BFG-9000. The part of the code that fires its tracers is hardcoded into the engine. The tracers recognize anything that can be shot as valid targets, so shoot-able gibs on the floor acts like a shield that protects enemies from the tracers, which are the weapon's signature mechanic. Current versions of GZDoom allow you to have more control over these tracers and what they can target, but Zandronum 2.1—which is built on GZDoom's code from literally five years ago—doesn't, and I refuse to abandon the Zandronum engine due its superior multiplayer.

Currently the BFG basically acts like a huge rocket launcher with a large splash damage that only hits enemies. The tracers still work, but they will just hit the gibs on the floor most of the time. Hopefully when things switch to Zandronum 3.0, I will be able to fix this.

I didn't realize all of the under-the-hood changes you made to weapons such as the shotgun. I only paid attention to surface details like alternate modes of fire like the chaingun's windup and the plasma rifle's charged shot. Did adding alternative modes of fire constitute creating new weapons as far as game balanced was concerned?

All alternate fires in Brutal Doom works like a commercial transaction: You have to give up something to get something else. The rifle for example, is already is the most accurate weapon of the game even when firing from the hip, but when you aim down the sights you trade two-thirds of your field of view. That makes it easier for flanking enemies to attack you without you noticing, but you practically get a full auto sniper rifle.

The plasma gun's "plasma shotgun" mode deals the same amount of damage as it would if you were to fire all these plasma balls with the regular automatic fire, but instead of firing them constantly, you can get into cover and wait for the volley to charge up, pop up and fire, then get back to safety to charge another volley without exposing yourself, and your payment for that is that these plasma balls are not as accurate in the regular mode.

The alt fires are basically made to make the weapons become more versatile and adapt to the player's playing style.

Brutal Doom lets players pick up weapons from fallen enemies, including the Mancubus' flamethrower and the Revenant's missile launcher.

Doom has bounced between action and horror since the original game in 1993. It's an action series where some iterations lean more heavily into horror than others. I always thought Doom 2 fell on the side of pure action, and Brutal Doom felt like an extension of that, at least to me. Did you see your mod as more of an extension of one classic Doom than another?

I think it's quite the opposite. The original Doom is much more action-packed than Doom 2: levels are smaller, songs have a faster tempo, you feel like a mad marine fighting for survival in a base infested by demons until you get sucked into hell and you mess things so bad that hell gets fed up with you, opens a portal back to Earth and wants you to get the fuck out. You know, this is actually the [sequel's] canon plot.

Doom 2 feels more like you are exploring the ruins of Earth. Many levels such as Downtown, Suburbs, and Industrial Zone are very wide, desolate, and non-linear, with more moody songs with a slower tempo. I had very different experiences with the classic Doom games growing up. My childhood memories of playing it on the Saturn, with PSX Doom's music and slow framerate, Doom was completely a horror game, then I rediscovered it on 2009 on the PC as an action game. I know that Doom exists in two completely different forms, but my priority with Brutal Doom is to allow players to choose the way they want to play the game.

You can play it fast on a skill such as Ultra-Violence, or one of the mod's custom skills such as Black Metal: You move faster, deal 50 percent more damage, and take double damage from enemy attacks. You can play as the Purist class to disable reloading, and load the "Doom Metal" collection which turns all midi songs into metal covers with actual instruments and adds into the action. Or you can play things slower, try the Realism mode which allows you to be instantly killed by two or three shots from a zombie's rifle or a single imp's fireball if you are without armor, requiring you to play extremely cautiously, and even load PSX Doom's soundtrack into it to make things more tense. It's up to you to choose the best experience that fits your taste.

Gore is usually the first thing players notice about Brutal Doom. Do you feel the gore gets undue attention at the expense of other features like the overhauled arsenal?

Yes. I see a lot of people refusing to play Brutal Doom because they think the added gore is too over the top and juvenile—and yet they refuse to acknowledge how absurdly over the top was the original game's gore, even for today's standards.

Brutal Doom has a lot of features that makes gameplay generally speaking smoother and faster, especially in co-op. For example, in Brutal Doom the players can't telefrag each other when walking over teleports at the same time, and plasma balls and rockets will fly through each other; firing a rocket and getting killed by it because your teammate runs in front of you at the exact time it fired is #1 cause of death on crowded co-op servers.

There is a feature that allows you to take a wounded zombie or imp and temporally use it as a shield so you can become a safe spot for your teammates to advance through a zone with lots of chaingunners. Version 21 will also add the ability to drop packs of ammo and a class that can carry medikits as inventory items and drop them for other players and act like some kind of medic.

Sgt. Mark IV exercised finesse to rig Brutal Doom's dismemberment and decapitation systems.

Brutal Doom lets players dismember enemies, such as shooting off limbs and performing headshots. That wasn't possible in the original game. How does dismemberment work? Is it as simple as some modern feature, or more than one, in a source port?

The ZDoom engine and its forks are capable of spawning objects as "projectiles" at any time, by any other object. It can also have properties that allows them to bounce on walls and floors before landing. Basically the gibs in Brutal Doom—and pretty much any other Doom mod—are actually projectiles; they are not much different from a rocket or an imp's fireball, they have their "spawn" state—when it's flying in the air—and their "death" state, when it hits something.

When a flying gib "dies"—hits the floor, stops bouncing—it spawns another gib that can be interacted with: shot into smaller meat chunks, kicked around, be tossed around by explosions.

But even with all the improvements of the ZDoom engine, the monsters can only have one rectangular hitbox. The solution for making localized damage was to spawn several actors with their own hitboxes around the monster on every frame they move.

Think of these hitboxes as meta-monsters: They have all the shoot-able properties of a Doom monster, but they are invisible, and are programmed to disappear a fraction of second after being spawned, so it can be replaced by a new hitbox at a new position as the monster moves around. When you shoot one of these hitboxes, they calculate the damage you caused to them, and transfer that damage to the monster who they belong with a multiplier. Hitting the head hitboxes transfers double damage, hitting the legs transfers half damage. 

If the monster is killed by this damage transferred by the fake hitbox, it plays a different death state depending of the amount damage transferred. You can notice that firing at a zombie's head with a shotgun makes a much bigger mess than firing at it with a rifle. The damage is transferred by the same system used by explosive barrels to damage things near it: the hitbox actually "explodes" when you shoot it. There are other less complex ways of doing this such as checking the height that a blood puff was spawned relative to the floor, but these methods makes an exact transference of damage amounts difficulty, especially with shotguns.

Weapons with area damage such as the rocket launcher ignores this system and plays random death animations instead. The small enemies have around three or four animations of them being tossed into the air and having their limbs ripped off by the explosion. Every death animation in a Doom mod needs to be drawn separately and coded into the game accordingly to the events that would cause such death animation to be triggered.

Freeing captured marines gives players allies in their battle against hell's hordes.

One of my favorite changes was replacing the blur artifact with a marine ally. What prompted you to swap out an artifact, rather than add another? Did you just consider blur to be less useful than other powerups?

I needed a way to include captured marines in the game. Brutal Doom is a mod that doesn't have a dedicated campaign, and is designed to run on the original levels and almost every user-made level, so I couldn't include them manually into the levels. Blur is often considered the most useless powerup in the game; it doesn't make you invisible to the monsters and instead, makes them shoot in random zig-zag patterns, which actually makes their projectiles harder to dodge. It was a rare powerup that you could be assured was found on most maps at least once, and it was a powerup that nobody would miss, so it was the best choice to make these captured marines spawn.

Recently on v20 the improved enemy AI is able to lose track of the player when going a long time without being able to see it, and wander around the map looking for the player. This script allows the enemies to actually become unable to see the player when cloaked. If the player makes noise or walks too close to the monsters they will be alerted for a moment, try to fire one or two times in the zig-zag pattern, then lose track of it and start wandering around again.

So the blur sphere is actually more useful now and I am thinking of ways to re-introduce it. Recently I added them as a rare powerup that can be randomly dropped by Spectres.

Brutal Doom is going strong, and so is the modding community for Doom and Doom 2. What do you think accounts for such longevity?

First, the game itself. Even with its sharp edges here and there, unmodded Doom still is an unique game with unmatched combat dynamics and level design. My first Doom experience was on fifth-gen consoles and I didn't experience the true fast gameplay of it properly until 2009, way after I had had enough of Call of Duty, so the "you are looking at it through nostalgia glasses" argument is not valid here. Not even other classic first person shooters of the 90s that came after it (Blood, Quake, Duke Nukem 3D) could reach the same level of perfection.

Second, the modding capacities of it. The source ports are really well made; you can learn how to make a weapons mod for GZDoom or Zandronum in a few weeks, learn how to make a map in just a few days, and there are very well organized documentation of the engines at the ZDoom wiki and it's really easy to get into it. 

When you get a game with unique mechanics that nobody ever succeeded at copying, a simple yet rich backstory full of spin-off possibilities, and the easiest to mod ever engine ever made, you get yourself a game that people will play for decades.