The Engine Inside Doom (1993) Built the Foundation for Every Game You Play Today

Key Takeaways

• •1993: Doom engine is the first widely licensed game engine
• •John Carmack coded it on NeXT computers — Steve Jobs' other company
• •Unity (2005) started as a web media tool, not a game engine
• •Today Unity and Unreal power 90%+ of all commercial video games

Timeline

Before 1993, every video game was built from scratch. If you wanted to make a game, you wrote everything — the renderer, the physics, the sound system, the input handling, the file loading — from zero. Every. Single. Time.

Then John Carmack changed everything.

When id Software released Doom on December 10, 1993, it wasn't just a game. It was an architecture. Carmack had designed the Doom engine so that game logic was cleanly separated from game content. Maps, textures, sprites, and sounds were stored in WAD files that could be created by anyone. The engine was the machine; the WAD was the game.

This wasn't just elegant engineering. It was a business model. id Software began licensing the Doom engine to other developers. Raven Software used it to build Heretic. Other studios followed. The concept of a "game engine" — reusable technology that powers multiple games — was born.

Before Doom, every game was built from scratch. After Doom, you could license the engine and just make the game. That one idea created a $200 billion industry.

Carmack coded the engine on NeXT computers (Steve Jobs' other company, after he was ousted from Apple). He used Objective-C and then ported to MS-DOS. The engine pioneered binary space partitioning (BSP) for fast rendering, texture mapping, and variable light levels — technology that seems basic now but was revolutionary in 1993.

Three years later, Carmack built the Quake engine — the first true 3D game engine, with real polygonal environments instead of the 2.5D trickery of Doom. The Quake engine became the foundation for Half-Life, Call of Duty, and Medal of Honor.

Meanwhile, a programmer named Tim Sweeney had been watching. He spent years building his own engine, which debuted with Epic Games' Unreal in 1998. The Unreal Engine was cleaner, more modular, and came with an editor that let designers build levels visually. Epic licensed it aggressively, and the Unreal Engine became the industry standard for AAA games.

Unity wasn't meant to be a game engine. It was supposed to compete with Adobe Flash. The App Store turned it into the most-used engine on Earth.

Then came Unity. Launched in 2005 by David Helgason, Joachim Ante, and Nicholas Francis, Unity wasn't originally intended as a game engine at all. It was a 3D web media creation tool, designed to compete with Adobe Flash. But when Apple launched the App Store in 2008, Unity added iOS support — and suddenly became the easiest way to make mobile games.

Unity's genius was accessibility. It was free. It supported multiple platforms. It had a drag-and-drop interface. Indie developers flocked to it. Today, more games are made with Unity than any other engine.

In 2015, Epic made Unreal Engine 4 free for all developers, taking a 5% royalty only after a game earns $1 million. This democratized AAA game development tools — anyone could now build with Hollywood-quality technology.

The root of every game you play today — from Fortnite to Genshin Impact to the indie game on your phone — traces back to a programmer at id Software in 1993 who decided that game code should be separate from game content.

John Carmack didn't just build Doom. He built the foundation that the entire game industry stands on.

How did this make you feel?

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