Karpathy Tests Opus 5: Reads a Passage from The Lord of the Rings and Gets Middle-earth for Just $10 - 36Kr

Andrej Karpathy asked Anthropic’s Opus 5 to build a browser-playable Three.js 3D game from the opening of The Lord of the Rings, and it produced a Middle-earth scene in about two hours.

The model wrote roughly 5,500 lines of code, showing how cheaply LLMs can generate highly customized interactive content.

Karpathy said this highlights the strong coding power of frontier models and their ability to create complex bespoke experiences quickly.

At the same time, the experiment exposed a key weakness: LLMs cannot directly perceive or verify their own outputs, so they rely on indirect checks like screenshots.

That self-validation gap is a major bottleneck for AI-generated code, virtual worlds, and future recursive self-improvement workflows.