$550, 8 Hours, and One Prompt: He Had Claude Build an FPS from Scratch

Felix Rieseberg posted on X. He wanted to test what Fable 5.2 could make with a one-shot prompt and no human feedback. The result was a first-person shooter: models, sound effects, and textures all generated from scratch, taking 8 hours and costing about $550 at API prices.

The prompt he gave was as follows:

You know, you should also build me a FPS. Insanely detailed quality pls, something that looks visually like it can keep up with AAA. Make it small in scope (like a tiny level) but otherwise impressive photorealistic graphics

In other words: build me an FPS. The visuals need to be insane, visually trading blows with AAA, keep the scope small—just a small level—but make the graphics photorealistic.

Billing details: about 2.7 million output tokens, 445 million input tokens, with a lot of cache hits, so the $550 figure is already a price reduced by caching.

The input token count is the real point

In the comments, John Rood's line is the one most worth screenshotting: one prompt, but 445 million input tokens show that it wasn't "one and done"—it was one instruction running for 8 hours.

That distinction is crucial. Many people see "one-shot," open a chat window, paste in a paragraph, hit Enter, wait two minutes, get a blocky character that can walk, and then conclude the model isn't good. The real process is: over 8 hours, the model repeatedly reads context, writes code, looks at results, and fixes things. The prompt is simple; the execution is not.

Felix himself put it more bluntly in a reply: the era of prompt engineering is basically over; now you just need to clearly state what you want. That carries weight coming from him—he is a core maintainer of Electron, not someone new to tools.

Where do the textures come from?

Gavin Guo asked a technical question: how are the textures rendered, and did it call an image-generation API?

Claude does not have an image-generation model. So those textures were most likely generated procedurally in code, or computed using things like canvas or shaders. Felix didn't explain in his reply how this harness was built, and Zac Yungblut asked the same thing and also got no answer.

This is probably the most worthwhile thread to keep pulling in the whole tweet: the more decent the visuals look, the more you need to know what it bypassed.

The onlookers split into two camps

One camp is playing. Someone modded the game to support a PS5 controller over USB, and it worked on the first try.

Someone said they played for a few minutes and the feel was surprisingly good—that surprised them more than the graphics. Someone got PTSD from the Arc Raiders-style drones in it. Jarrod Watts directly posted an image saying the graphics really do look like AAA.

The other camp is throwing cold water. The reply from account X is fairly representative: here we go again, another round of "one-shot" and Blender demos, a pile of games nobody will play and websites nobody will visit, all dumped in the first three days of a new model release—can we just skip ahead to the part where Anthropic nerfs the model and everyone goes home?

Operator takes the other extreme: GTA 6 will be the last AAA game made by a traditional game studio, and this tweet is proof—and the model was only released today.

Neither side is hitting the point.

How to read $550

This number is more informative than the visuals. Traditional AAA means hundreds of millions of dollars in budget, hundreds of people, and several years. Here it's 8 hours and one API key. The gap is orders of magnitude.

But don't rush to extrapolate. Felix only made that one prompt public; he didn't disclose what environment he ran it in, how he organized context, or how he corrected course along the way. A systems-savvy person getting good results with a simple prompt does not mean typing the same words into a chat box will reproduce it. That gap is exactly what those 445 million input tokens filled.

You can click in and play the game yourself: https://claude.ai/artifact/BGY1SztrAYcJQHSsnHHGmp

One question nobody has answered yet is where the textures actually came from. Until Felix releases the trace someday, this tweet isn't complete.