Andrej Karpathy vibe-coded a scene from Lord of the Rings. It looks janky! (but it's kind of wild that you can just spin up a world model like this with plain Opus 5)
Andrej Karpathy — co-founder of OpenAI and Tesla's former AI director — wrote a long post on X about how the way we test large language models is changing (he's currently leading pretraining at Anthropic). I'm recapping his tweet and the video he made, with some added context, and attaching it below.
His point: we used to prompt AI with things like "draw a pelican on a bicycle." Now models can put together entire custom worlds for pocket change — the kind of thing no sane human would ever build by hand.
Karpathy fed Claude Opus 5 the first paragraph of *The Lord of the Rings*, gave it a budget of roughly a million tokens — about $10 — and asked it to render the story in Three.js.
The model worked for about two hours and wrote 5,500 lines of code. The result: a procedural, low-poly rendering of the Shire, complete with animation, hobbits, treasure, and subtitles.
It looks rough, but it works.
That's exactly what Karpathy sees as the real shift:
> this is an example of us going from thoughts like "haha no one is going to build this stupid thing" to the more insidious "well why not, it's almost free anyway"
When an experiment costs a few dollars instead of real effort, a whole category of ideas that used to be pointless to even start suddenly opens up. You could turn a book paragraph into an interactive story, a chat log into a game, an archive into a virtual museum, or any text into a tiny GTA-style world.
There's one real limitation, though: models still aren't great at checking their own work. They can't properly watch video, play through the game they built, or spot every visual glitch. That's why Claude spent so long taking screenshots, making mistakes, and ultimately left behind a pretty "janky" result.
The next big step isn't just generating more code — it's closing the loop:
build → run → spot the error → fix it → repeat.
Source and player are already up:
https://karpathy.ai/lotr-movie/
Looks like we'll soon be cranking out GTA-style worlds from any piece of text.