Tim Sweeney says AI took over the routine 70% of engine coding he did on Unreal Engine 1 and is now solving hard problems too
When I was writing Unreal Engine 1, my time was divided as follows: - Around 30% went to seriously deep coding on hard problems: assembly language texture mappers, C++ BSP trees, data persistence, object oriented systems design, and networking. - Around 70% was just typing and refactoring large bodies of code needed for a complete engine feature set. This was not hard, and while I was doing it my mind was mostly on the deeper coding topics, thinking and planning for what's next. It didn't feel much different from vibe coding today, except that it was just me typing code on an IBM Model M keyboard rather than prompting it and reviewing the results. So, it has always seemed perfectly logical that we would rely on AI for that 70%, once the AI could do it with a similar quality standard as we could, which has never been perfection. It came as no surprise that, after a few years of AI model evolution, it was able to take the reigns on that 70% and free up programmers' time for more valuable tasks. What's more of a surprise is the emergence of AI as a sort of insta-Carmack able to solve hard technical problems quite cleverly and often cleanly, and that it's able to reason about and work in complex 3D scenes both by operating the tools and by directly understanding the raw data files. I abandoned assembly language in 1998 when out-of-order CPUs made much simpler C/C++ code faster, and never I missed it. If prompting through architectural documents, concept art, and design plans can transcend typing code and tweaking vertices, that will enable developers to spend their time on higher-level, higher value technical and creative tasks. What matters is the end product, whether it's a game or an engine. Anything developers can do to try out more ideas and make better software and games faster is a win for everyone.
Context
The head of Epic Games is arguing that AI coding is a natural step for game developers, a view that many in the industry dispute.
This is a first hand opinion from Sweeney, the founder and chief executive of Epic Games, which sells tools for game developers. It is his recollection of his own work and his view of AI, not a measured study.
Deep dive
On October 17, Tim Sweeney wrote that when he was writing Unreal Engine 1, about 30% of his time went to seriously deep coding on hard problems, such as assembly language texture mappers, C++ BSP trees, data persistence, object oriented systems design and networking.
The other 70%, he wrote, was just typing and refactoring large bodies of code needed for a complete engine feature set. He said it was not hard, his mind was mostly on the deeper problems while he did it, and it didn't feel much different from vibe coding today, except that he was typing on an IBM Model M keyboard rather than prompting and reviewing the results.
Sweeney said it always seemed logical to rely on AI for that 70% once it could match human quality, which has never been perfection, and that it came as no surprise when it took over that work. What surprised him more, he wrote, is AI emerging as a sort of instant John Carmack, able to solve hard technical problems cleverly and work in complex 3D scenes, both by operating tools and by reading raw data files.
He compared the change to his dropping assembly language in 1998, when newer processors made simpler C and C++ code faster, and wrote that what matters is the end product. Anything that lets developers try more ideas and make better games faster, he said, is a win for everyone. Elon Musk reposted it, and it passed 1.3 million views.
What to expect next
Watch how game developers respond, since many artists and programmers have pushed back on AI in games and on Epic's support for it.
Also watch what Epic ships for Unreal Engine, whose official plugin for Claude Code spread widely on X this week, and whether Sweeney's view that AI can handle hard engine problems holds up in real projects. Debates over labeling AI use in games are likely to continue.