id Software

DOOM fights force four decisions at once: priority, preference, preservation, position. In every fight the player decides which enemy to hit, which weapon to use, how to recover health, ammo and armour, and where to move. All four are weighed together and re-weighed whenever something changes, which is what makes the combat feel intense.

Running out of ammo can turn the priority from a boss into shotgunning a zombie. Other shooters feel calmer because each common convention removes a question: look-alike enemies remove priority, two-weapon limits remove preference, and regenerating health with cover removes preservation and position. "All four Ps must be considered simultaneously, and constantly reevaluated as the new information arises."

Fights unfold as phased spawn waves triggered by the player's progress. The five-minute Nekravol Part II fight in DOOM Eternal opens with two phases of small, fast enemies, each starting after a handful of kills, then chains big demons, each triggered by hurting the last.

The Pain Elemental brings Whiplashes when its health drops to a third, and the Doom Hunter opens the final phase, with Prowlers arriving when he falls to half. The set triggers give each run a predictable rhythm that is never exactly the same, and leaving big demons alive means juggling many monsters at once.

Each enemy has a distinct threat and a best counter, inviting target and weapon choices. The slow Mancubus can be ignored while the aggressive Baron of Hell demands focus; the Revenant's missile barrage and the Pain Elemental's endless spawning make them early targets. Counters include the rocket launcher for the Mancubus, the ballista for the flying Pain Elemental and the plasma rifle for the Doom Hunter's shield.

Gear adds to the choice: freeze bombs stop teleporting Prowlers, the blood punch hurts the Doom Hunter's shield, and the BFG and crucible are emergency cards to time well. Because each tool answers a different enemy, the player never settles on one.

Enemies double as loot crates so the player keeps attacking to survive. Map pickups run out, so health comes from glory kills on staggered enemies, ammo from the chainsaw and armour from the flame belch. Zombies respawn forever, barely do damage and die in a split second, existing mainly to feed the player.

Arenas are designed like multiplayer maps, with routes, elevation and no cover. The Nekravol chamber is large and symmetrical, with raised platforms, ramps, toxic pools and scattered items; monkey bars link the three highest areas without touching the ground. With no cover and enemies punishing standing still, players pick routes by where they need to go.

Each enemy pushes a kind of movement: the Baron of Hell makes you backpedal and the Revenant's lock-on missiles force jumps and dashes. "This allows you to move around unimpeded by obstacles, while picking between different routes, depending on where you need to go, and what you want to do."

DOOM Eternal weakened the balance by pushing players toward single answers. Weapon-specific weaknesses, like a sticky bomb in a Cacodemon's mouth that staggers it instantly, and must-kill enemies like the Archvile and Buff Totem shrink the choice of targets and weapons.

Eternal also massively reduced max ammo and made the flame belch necessary for armour, so players can spend more time patching up than slaying demons. By contrast, DOOM 2016's Summoner and the Pain Elemental can be ignored for a while without overwhelming you.

Doom (2016) removed every shooter convention that costs the player speed. id dropped aim down sights, made the player equally accurate while running and let them strafe as fast as they run, so shooting never slows you and you can orbit enemies while firing.

The game was made as a gory tribute to 90s game design. "id forcefully rejected just about every piece of shooter design that has been employed to slow this genre down."

id gave away Wolfenstein 3D's first levels free and sold the rest. id hosted the first few levels on its FTP server; players who liked it mailed money and received the rest of the game by post. Doom then set off the first-person shooter boom.

The route let small teams like id start without publishers or retail shelf space. PopCap later revived the same model for Bejeweled, Bookworm and Peggle.

Small teams keep bets cheap enough to try unproven ideas. Wolfenstein 3D had 10 people in its credits. Low cost and team size let early makers take chances without proof of demand, while 100-plus person, tens-of-millions budgets later made publishers risk averse.

"It was a little less risky, so we could take a chance with games."