Dev vibe-codes a 30,000-citizen simulated London city builder entirely with Claude Code
ragmondo · reddit · 2026-10-19
A developer built Civitas, a 3D multiplayer browser city builder (three.js + TypeScript + Node) written almost entirely by Claude Code — free read-only London demo (real coordinates, 30 landmarks, 3 Tube lines, 30,000 individually simulated citizens) plus open source. The workflow is the interesting part: one Claude Code session acts as coordinator, breaking features into kanban tasks via MCP and dispatching to subagents (Opus for simulation/networking, Sonnet for rendering/UI). Each subagent works in its own git worktree and runs the project's own checks before handoff — typecheck, building-catalogue validator, a demo check that seeds twice and compares hashes, tick-cost load tests. The coordinator merges, re-runs checks, deploys. The author's instructions were short ("boats and ports next"); the value came from pushback — e.g. after reporting cars still driving on Tower Bridge mid-lift, Claude tied road barriers to the lift schedule and added a regression test, and a frank self-audit turned weaknesses into acceptance-tested cards.
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