Claude Code Builds Universe Atlas in a Week

chrisjz · reddit · 2026-07-16

Using Fable 5 and Claude Code, a developer created a true-scale universe atlas (universeatlas.org) in about a week. It allows users to browse galaxies, stars, planets, satellites, and black holes within a single, continuous zoom view.

Scale & Implementation

Covers roughly 8.4 million real stars and 2.6 million SDSS galaxies.
The codebase is around 14,500 lines of TypeScript / WGSL, merging 92 PRs and 237 commits.
The engine is just 90 kB gzipped, with zero runtime dependencies, no game engine, and built directly on WebGPU.

The Role of AI

Almost all code was generated by Fable, including the renderer, orbital mechanics, and data pipelines.
It also includes modules for Kepler solvers, SGP4 satellite propagation, planetary atmospheric ray marching, and black hole gravitational lensing.
The author primarily handled code review, merging, and hunting for bugs during actual usage.

Quality Assurance

Planet positions are checked against JPL Horizons in CI; tests fail if the error exceeds 0.2 degrees.
The data generator has physics gates to prevent outputting incorrect tiles.
CI actually renders WebGPU scenes and performs pixel-level comparisons.
Every view has a deterministic URL, making it easy to reproduce bugs directly for the model to fix.

The post also includes several quick-jump observation points, such as the black hole at the center of the Milky Way, solar eclipses, Io's shadow, Voyager 1, and Halley's Comet.

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Claude Code Builds Universe Atlas in a Week

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