Doom: The Game That Launched First-Person Shooters
Photo: Alberto Morales / Pexels
In December 1993, a five-person team working out of a rented office in Mesquite, Texas released a shareware game that would rewrite the rules of interactive entertainment. Doom was not the first first-person shooter — id Software's own Wolfenstein 3D, released a year earlier in May 1992, holds that title. But Doom was the game that took the format and turned it into something faster, darker, and technically superior in almost every way. This is the story of how id Software built it, why the id Tech engine underneath it mattered, and why the formula still drives the genre more than three decades later.
Before Doom: id Software and the shareware gamble
id Software was founded in February 1991 by four employees of a Louisiana software company called Softdisk: programmer John Carmack, designer John Romero, artist Adrian Carmack (no relation to John), and business lead Jay Wilbur. The team had already made waves with Commander Keen, a side-scrolling platformer that proved PC games could match the smooth scrolling of console titles, and then with Wolfenstein 3D, the game that first popularized the run-and-gun, first-person perspective on home computers.
Wolfenstein 3D used a raycasting engine, a rendering trick that simulated a 3D world using flat, single-height walls arranged on a rigid grid. It worked, but the levels felt like mazes rather than places. id's next project needed rooms with different ceiling heights, diagonal walls, and levels of light and shadow. That meant a new engine, built by John Carmack, the programmer whose name would become inseparable from the genre he helped create.
The company distributed its games as shareware: give away the first episode for free, let word of mouth (and floppy disks passed between friends and traded on early bulletin board systems) do the marketing, then sell the rest of the campaign directly by mail order. It was a radical bet on a business model nobody in retail software believed in. Doom's first nine-level episode was uploaded to a University of Wisconsin FTP server on December 10, 1993, and within about two years an estimated 15 to 20 million people had played it, according to reporting compiled from the era's shareware distribution records (TechSpot). Some university IT departments reportedly had to ban the game from campus networks because so many students were playing deathmatch simultaneously that it choked bandwidth.
The engine: how id Tech 1 made Doom possible
Doom's technical leap over Wolfenstein 3D came down to one algorithmic decision: binary space partitioning, or BSP. Think of a BSP tree like a filing system for a room's geometry. Instead of asking the computer to check every wall and object in a level against the player's line of sight every single frame — an approach that gets exponentially slower as levels get bigger — a BSP tree pre-sorts the level's geometry once, offline, before the game ever runs. It recursively splits the map into convex chunks along dividing lines, building a tree structure that tells the renderer exactly which chunks are in front of which, from any viewpoint, without having to recalculate that ordering on the fly.
That precomputation is what let Doom draw front-to-back, skip surfaces that were hidden behind others, and still hit playable frame rates on a 386 or 486 PC with as little as 4 megabytes of RAM. Carmack had experimented with BSP concepts in a Super Nintendo port of Wolfenstein 3D before folding a full BSP renderer into Doom sometime between the game's alpha build in May 1993 and its public beta that October (DoomWiki, cited via TechSpot reporting). It was, according to a widely cited analysis of the technique, close to a solved problem in academic computer graphics research — Carmack's contribution was recognizing it could run in real time on consumer hardware and shipping it in a commercial game months later.
The result is often labeled "2.5D" rather than true 3D. Doom's levels could vary in height and have sloped-feeling floors through clever texture tricks, but two rooms could never be stacked directly on top of one another the way they can in a fully three-dimensional engine like Quake's, which Carmack built two and a half years later. That constraint was not a failure of ambition. It was a deliberate trade: give up full verticality in exchange for speed, and let the speed define everything else about how the game feels.
What is id Tech, and how did it evolve?
Id Tech is the umbrella name applied retroactively to the sequence of proprietary engines id Software built starting with Doom's renderer (now called id Tech 1). Each generation traded one technical constraint for a bigger one: id Tech 1 (Doom, 1993) used 2.5D BSP rendering; id Tech 2 (Quake II, 1997) added full 3D with hardware-accelerated OpenGL rendering; id Tech 3 (Quake III Arena, 1999) refined multiplayer netcode and curved surfaces; id Tech 4 (Doom 3, 2004) introduced per-pixel dynamic lighting and shadows; id Tech 6 and 7 (Doom 2016 and Doom Eternal) power the modern reboots with physically based rendering pipelines optimized for consistent high frame rates.
The weapons, the pacing, and why Doom feels like Doom
Doom's arsenal became a template the entire genre still borrows from: a starting pistol with unlimited but weak ammunition, a shotgun that reloads faster than most later FPS shotguns and remains satisfying to fire even 30 years on, a chaingun for suppression, a rocket launcher that trades area damage for the risk of hurting yourself at close range, a plasma rifle, and the BFG9000, whose absurd one-shot damage output is rationed by scarce ammo. Each weapon occupies a distinct tactical niche, so switching between them mid-fight is not cosmetic. It is the core skill the game is testing.
That arsenal exists inside a pacing structure built entirely around forward motion. Demons spawn in waves and from multiple directions, health and ammo pickups are scattered generously through the level rather than hoarded behind puzzles, and standing still is punished immediately by incoming fire from monsters the player cannot always see coming. This pushed players toward what the community later called circle-strafing: continuously moving in an arc around an enemy while facing and firing at it, a technique that barely existed as a concept before Doom because earlier games rarely demanded that kind of continuous evasive movement from the player.
Players also discovered that Doom's movement code let you gain speed by moving diagonally and adjusting your input at specific angles, a side effect of how the engine calculated velocity along the X and Y axes independently rather than a true diagonal vector. This "strafe-running" trick was not designed intentionally, but the community built entire speedrunning strategies around exploiting it, and later arena shooters like Quake formalized similar movement quirks (bunny-hopping, rocket-jumping) into core mechanics rather than treating them as bugs.
Network multiplayer: deathmatch before the internet was mainstream
Doom is widely credited as the game that popularized competitive multiplayer deathmatch. Up to four players could connect over a local network or, more commonly for players outside university computer labs, over a modem using a null-modem cable or dial-up services like DWANGO (Dial-up Wide-Area Network Game Operation), a commercial matchmaking service built specifically to let Doom players find opponents outside their immediate physical location.
Deathmatch mode pitted players directly against each other rather than against the game's AI, and cooperative mode let two to four players fight through the demon-infested campaign together. Neither mode invented online competitive gaming outright — text-based MUDs and a handful of earlier titles had networked play — but Doom's combination of accessible modem play, a large and enthusiastic player base, and a genuinely fast, skill-rewarding shooter turned deathmatch into a cultural reference point. The term "deathmatch" itself, now standard across nearly every competitive shooter, entered common gaming vocabulary through Doom.
Why did Doom's source code release matter so much?
id Software released Doom's source code publicly on December 23, 1997, initially under a permissive but non-open license, then formally re-released it under the GNU General Public License on October 3, 1999 (Wikipedia, Doom engine, summarizing id Software's release history). That decision let programmers outside id legally study, modify, and redistribute the engine, which directly enabled the source port ecosystem that keeps Doom running on modern operating systems, and famously on everything from graphing calculators to smart refrigerators to oscilloscopes — the origin of the long-running "but can it run Doom" meme.
Modding, WAD files, and the community that never left
Even before the source code release, id Software built Doom to be modified. The game's levels, textures, sounds, and sprites were stored in WAD files (an acronym for "Where's All the Data"), a container format designed explicitly to let players swap in custom content without touching the game's executable code. This was a deliberate design choice, not an accident of the codebase, and it meant a community of level designers and modders sprang up almost immediately after release, well before anyone had access to the underlying engine source.
That community has not stopped working in the 30-plus years since. According to ModDB's cataloging of Doom-engine projects, the ecosystem includes thousands of user-made total conversions, campaign packs, and gameplay mods, and doomworld.com's /idgames archive alone hosts tens of thousands of individual user-submitted WAD files spanning three decades of releases. Prominent modern total conversions like Brutal Doom, which overhauled the combat with gorier kills and expanded weapon mechanics, and community megawad projects that add entirely new 30-plus level campaigns, are released on a near-monthly basis by an active mapping community that treats the original 1993 engine as a living platform rather than a museum piece.
Which source ports keep Doom playable today?
Modern players rarely run the original 1993 executable. Instead, community-built source ports translate the original engine's logic to modern systems: Chocolate Doom prioritizes bit-for-bit historical accuracy with the original DOS release, GZDoom adds modern lighting, higher resolutions, and extensive scripting support for ambitious total-conversion mods, and Zandronum focuses specifically on stable, low-latency online multiplayer. All three remain under active development.
The 2016 reboot and Doom Eternal: proving the formula still works
After a string of licensed-out sequels and a divisive 2004 survival-horror pivot with Doom 3, id Software returned to the franchise's arena-shooter roots with Doom (2016). The game's central design mechanic, Glory Kills, let players execute melee finishers on staggered enemies to recover health, which converted the traditionally "weak" melee attack into an active resource-management decision rather than a last resort. Doom 2016 sold roughly 957,000 digital copies at launch across platforms, a strong number for a single-player-focused reboot of an older franchise (TweakTown, citing NPD/platform sales data).
Doom Eternal, released in March 2020, more than tripled that pace: roughly 3 million digital units sold across platforms in its launch month alone, according to sales tracking reported by TweakTown, and it went on to generate more than $450 million in revenue within its first nine months on sale, per figures reported by VGChartz (VGChartz). Eternal pushed the Glory Kill and resource-loop concept further with the "push forward combat" philosophy: players are deliberately starved of ammo and health at rest, forcing them to actively engage enemies with specific weak-point weapons, chainsaw kills for ammo, and flame-belch attacks for armor, turning every encounter into a constant, high-speed resource puzzle rather than a static gunfight.
Doom versus tactical shooters: two opposite design philosophies
| Design element | Doom (1993–present) | Modern tactical shooters (Counter-Strike, Valorant) |
|---|---|---|
| Movement speed | Very high; constant motion expected | Deliberately slow; positioning over speed |
| Health/ammo economy | Abundant; player rarely starved outside Eternal's forced-engagement loop | Scarce; every bullet and life matters |
| Core skill tested | Reflexes, weapon-switching, spatial awareness | Map knowledge, patience, team communication |
| Death penalty | Instant respawn, low stakes per death | Round-based, one life per round, high stakes |
| Player fantasy | Unstoppable, overwhelmed by hordes but powerful | Vulnerable operator managing risk |
| Multiplayer structure | Free-for-all deathmatch, chaotic | Structured 5v5 rounds, economy management |
Table: How Doom's original arena-shooter design compares to the tactical-shooter branch of the FPS genre it helped create.
This divergence was not accidental drift. As the genre matured through the late 1990s and 2000s, some developers doubled down on Doom's speed-and-chaos formula (Quake, Unreal Tournament, and eventually Doom 2016 and Eternal itself), while others, starting with Counter-Strike as a 1999 Half-Life mod, deliberately built the opposite experience: slow, cautious, round-based, and built around economy management rather than reflex tests. Both branches trace their DNA back to Doom, either by extension or by explicit rejection of its design choices. Doom proved fast, arcade-style shooting could work commercially; tactical shooters proved that removing that speed entirely could work just as well, for a different kind of player.
Level design: mazes with intent
Wolfenstein 3D's levels were, by design, literal mazes: grid-aligned, uniform in height, and navigated largely by memorization. Doom's level designers, chiefly John Romero, Sandy Petersen, and American McGee, used the new engine's variable room heights and non-grid-aligned walls to build spaces that felt like places rather than puzzles: industrial bases with control rooms and storage bays, and later, hell-scapes with organic, cavernous geometry that would have been impossible in the earlier engine.
Key-and-lock progression (find the red keycard to open the red door) gave players a light structure to navigate by without forcing linear corridors, and secret areas hidden behind fake walls or triggered by specific switches rewarded players who explored rather than rushed. This blend of structure and freedom became a reference point cited by later level designers across the industry, including in official retrospectives id Software has given on the franchise's 30th anniversary re-releases.
What people get wrong about Doom
The most common misconception is that Doom invented the first-person shooter outright. It did not. Wolfenstein 3D, released by id Software itself in May 1992, predates Doom by roughly a year and a half and already established the run-and-gun, first-person perspective. What Doom did was refine nearly every element of that formula at once: better lighting and level geometry through BSP rendering, a more varied and satisfying weapon roster, smarter and more varied enemy AI, and, critically, accessible network multiplayer that Wolfenstein 3D never offered. Doom did not invent the genre. It perfected the version of the genre that everyone remembers.
A second misconception is that the 2016 reboot and Doom Eternal are nostalgia-driven cash grabs riding on the original's name recognition. The sales and revenue figures above suggest the opposite: both games succeeded on mechanical merit with a generation of players who, in many cases, never played the 1993 original. Eternal in particular is frequently cited by reviewers and speedrunners as faster and more demanding of precise play than any individual level from the original trilogy, not because it copies 1993 mechanics wholesale but because it re-derives the same design principle (constant forward pressure, resource management through aggression) using tools the original engine could never have supported.
A third misconception worth addressing: that Doom's hellish, demonic aesthetic was an obvious or safe choice for 1993. It was not. Most action games of that era, including id's own Wolfenstein 3D, used a militaristic or science-fiction setting. Mixing Martian science-fiction hardware with occult, hell-invasion imagery was a genuinely unusual creative swing for a mainstream commercial release, and its distinctiveness is part of why the aesthetic stuck in players' memory well enough to still define the franchise's visual identity three decades and multiple reboots later.
Speedrunning: Doom as a solved, contested game
Doom has one of the longest-running competitive speedrunning communities in gaming, tracked in detail on Doom-specific leaderboards and archives maintained separately from general speedrunning aggregators, alongside listings on Speedrun.com. Categories range from casual "any percent" runs to strict 100 percent kill-and-secret completions on the hardest Ultra-Violence difficulty, and runners exploit both intentional design (fast weapon-switching, careful pathing) and unintentional engine quirks (wall-running through specific texture seams, sequence breaks that skip entire sections of a level by exploiting collision detection edge cases). The Doom speedrunning community's continued activity, more than three decades after release, is itself evidence for how tightly the original level design and engine mechanics interlock: there is enough depth in the movement and combat systems that players are still finding new optimizations.
The takeaway
Doom did not invent the first-person shooter, but it is the game that made the genre commercially and technically credible, and the reason for that success was never one single feature. It was John Carmack's BSP-based id Tech 1 engine making complex, varied-height levels run smoothly on consumer hardware, combined with a design philosophy that trusted speed, abundant resources, and constant forward momentum over caution. That same philosophy, refined but structurally intact, is what makes Doom Eternal one of the fastest, most demanding shooters on the market today, more than 30 years after a five-person team in Texas uploaded nine levels to a university FTP server and changed what a shooter could be.
Frequently Asked Questions
Q: Did Doom invent the first-person shooter genre? A: No. id Software's own Wolfenstein 3D (May 1992) predates Doom by about a year and a half and already established the run-and-gun, first-person format. Doom refined the formula with better level geometry via BSP rendering, a stronger weapon roster, and accessible network multiplayer, which is why it is remembered as the genre's defining game rather than its first.
Q: What made Doom's engine technically important? A: Its use of binary space partitioning (BSP), a technique that pre-sorts a level's geometry into a tree structure before the game runs, letting the renderer draw only visible surfaces without recalculating visibility every frame. That let Doom run complex, multi-height levels smoothly on 1993-era PCs with as little as 4 megabytes of RAM (TechSpot).
Q: How many people played the original Doom shareware release? A: Reporting on id Software's shareware distribution estimates 15 to 20 million players within roughly two years of the December 1993 release, spread through free redistribution on bulletin board systems and university networks rather than traditional retail sales.
Q: When was Doom's source code released, and why does that matter? A: id Software released the source publicly on December 23, 1997, and formally re-licensed it under the GNU General Public License on October 3, 1999 (Wikipedia). That release legally enabled the community-built source port ecosystem (Chocolate Doom, GZDoom, Zandronum) that keeps the game running on modern hardware.
Q: Is Doom Eternal actually harder than the original Doom? A: They are difficult in different ways. Original Doom's Nightmare difficulty made specific sequences brutal through constantly respawning enemies. Eternal demands sustained rhythm across an entire fight, forcing players to juggle chainsaw kills for ammo, flame-belch attacks for armor, and Glory Kills for health simultaneously. Reviewers and speedrunners generally describe Eternal as more mechanically demanding moment-to-moment, even if original Doom's toughest sequences remain punishing in their own right.
Q: How did Doom popularize online multiplayer deathmatch? A: Doom let up to four players connect over a local network or a modem, including through commercial dial-up matchmaking services like DWANGO built specifically around the game. Its combination of a large player base and genuinely fast, skill-testing combat is why "deathmatch," a term the game helped popularize, became a standard mode across nearly every FPS that followed.
Q: What is a WAD file, and why did it matter for modding? A: WAD (Where's All the Data) is the container format id Software used to store Doom's levels, textures, and sounds separately from the game's executable code. That separation let players create and share custom content legally and easily well before the engine's source code was released in 1997, seeding a modding community that predates most other games' mod scenes by years.
Q: How much revenue did Doom Eternal generate? A: Doom Eternal sold roughly 3 million digital units in its launch month (March 2020) and generated more than $450 million in revenue within its first nine months on sale, according to sales-tracking reports (VGChartz). It also became Steam's best-selling release of 2020, outperforming Half-Life: Alyx.
Q: Why do so many later games copy Doom's hellish, demonic aesthetic? A: Mixing science-fiction hardware with occult, hell-invasion imagery was an unusual creative choice for 1993, when most action games leaned militaristic. The distinctiveness of that combination is part of why it became so memorable, and countless later action games borrowed hell-invasion and demon-slaying tropes as a recognizable, proven aesthetic shorthand for high-intensity combat.
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About the Author
SciHub101 is an independent science and technology publication founded and edited by Buğra Sözeri, a software engineer and app developer based in Türkiye. AI tools assist with drafting and research. Source documentation in the existing archive is uneven, and articles are being reviewed and corrected. The Editorial Team byline identifies editorial responsibility; it does not certify specialist or independent human review. Where we compare products, anything built by our own team is labelled as such — see the editorial guidelines and About page for how corrections and disclosures work.
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