John Carmack: Doom, Quake, VR, AGI, Programming, Video Games, and Rockets | Lex Fridman Podcast #309

Carmack traces his path from teenage assembly-language games on a borrowed PC to inventing the scrolling and 3D-rendering tricks that built id Software's empire. He digs deep into the technical innovations behind Wolfenstein 3D (ray casting, compiled scalers), Doom (BSP trees, modding), and Quake (true 3D, networking, his own scripting language), alongside lessons on programming philosophy, user value, and hard work. The conversation moves through his Oculus/Meta years and a candid critique of why big tech wastes resources, his friendship and engineering debates with Elon Musk, and bets on Mars and self-driving cars. The back half centers on his conviction that AGI is achievable within a decade, likely in tens of thousands of lines of code, and why he's now committing fully to it. It closes on martial arts, books, mortality, and the meaning of life.

• Reveals he nearly chose cost-effective nuclear fission over AGI as his next major life project.
  00:25:54
• Admits he pushed John Romero out of id Software and says a different corporate structure could have avoided the tension.
  03:08:12
• Says Meta spends $10 billion a year on Reality Labs and it makes him feel sick to his stomach.
  03:38:50
• Made a $10,000 bet that there will NOT be boots on Mars by 2030, against a room of optimists.
  03:50:41
• Claims AGI code will likely be tens of thousands of lines, writable by one person, needing fewer than six key insights.
  04:04:17
• Just signed a term sheet taking investor money to go all-in on AGI after two years as a self-funded 'gentleman scientist'.
  04:40:19
• Bought a quarter-million-dollar DGX Station specifically so it would 'mock' him into running more experiments.
  04:48:06
• Sam Altman tried to recruit him to OpenAI, and Ilya Sutskever gave him a binder of papers to learn machine learning.
  04:45:30

• Carmack drinks about eight or nine Diet Cokes a day and treats cracking one open as his signal to start working.
  00:56:30
• At id Software he had a pizza delivered every single day for years, and the shop never raised his six-year-old price.
  00:54:55
• He runs his C/C++ code in a debugger constantly, setting a breakpoint and stepping through every new function he writes.
  01:08:23
• He once spent a week forcing himself to use classic vi, calling it his 'Civil War reenactment phase' before happily returning to Visual Studio.
  01:11:53
• Carmack and Tom Hall cloned the first level of Super Mario Bros 3 on PC overnight, titled 'Dangerous Dave in Copyright Infringement'.
  01:47:53
• id Software first tried to license Super Mario 3 for PC from Nintendo, who looked at it in Japan but passed.
  01:49:26
• It was an innovation in Doom to remove 'lives'; earlier games like Wolfenstein still had three lives and extra-life powerups.
  02:14:55
• Building Quake's own programming language (QuakeC) taught a whole generation to program, though Carmack says it was 'nothing to write home about'.
  02:53:35
• The most popular VR app turned out to be Beat Saber, which nobody predicted; first-person shooters underwhelmed in VR.
  03:23:16
• Carmack notes that tapping to a choke in grappling is a closer brush with mortality than most people consider.
  05:01:33