Solo dev builds three.js desert racer with Opus 5.5: a 4-day AI-assisted game dev log

Promptmethus · x · 2026-10-08

A Japanese developer (lutaai) shared a detailed log of building a three.js desert racing game with Opus 5.5:

Fixing character models: A T-pose model bent into a riding pose caused skin folding and artifacts at certain camera angles. Regenerating the character in a riding pose via GPT + Meshy 3D, then rebinding bones, removed nearly all distortion.
Meshy pitfalls: Meshy exports have vertices split per texture island (overlapping but unwelded), so moving them tears holes — merge coincident vertices first. Bone alignment was thrown off 62° by hair geometry; aligning on a distinct horn-like feature fixed it.
Speed feel: 600 km/h made the character fly off and hard to see, so speed was capped at 300 km/h, with wind particles and ground texture flow conveying velocity. The hardest part was communicating 'doesn't feel fast' to the AI — an overhead diagram marking particle sources/flow finally located the mismatch.
Performance: 40k polygons for the character alone, 60fps with gates and rocks included.
Workflow gains with Opus 5.5: commit before each experiment so discarding is cheap; extract enemy movement into a standalone 120s test verifiable numerically; fast research-implement loops crush his own assumptions.
Caveat: AI suggestions skew additive; only adding features adds complexity, and fast iteration helps find the 'simple but not monotonous' point.

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