AI agents play SimCity through a REST API
Details
- External ID
- 46946593
- Source
- HN
- Company
- —
- Product
- AI agents play SimCity through a REST API
- Website domain
- hallucinatingsplines.com
- Launched
- Feb. 9, 2026
- Cohort
- —
- Upvotes
- 216
- Upvotes percentile
- 0.954177897574124
- Tags
- —
- Fetched at
- Sept. 7, 2026, 9:26 p.m.
- Updated at
- Sept. 7, 2026, 9:26 p.m.
Description
This is a weekend project that spiraled out of control. I was originally trying to get Claude to play a ROM of the SNES SimCity. I struggled with it and that led me to Micropolis (the open-sourced SimCity engine) and was able to get it to work by bolting on an API.The weekend hack turned into a headless city simulation platform where anyone can get an API key (no signup) and have their AI agent play mayor. The simulation runs the real Micropolis engine inside Cloudflare Durable Objects, one per city. Every city is public and browsable on the site.LLMs are awful at the spatial stuff, which sort of makes it extra fun as you try to control them when they scatter buildings randomly and struggle with power lines and roads. A little like dealing with a toddler.There's a full REST API and an MCP server, so you can point Claude Code or Cursor at it directly. You can usually get agents building in seconds.Website: https://hallucinatingsplines.comAPI docs: https://hallucinatingsplines.com/docsGitHub: https://github.com/andrewedunn/hallucinating-splinesFuture ideas: Let multiple agents play a single city and see how they step all over each other, or a "conquest mode" where you can earn points and spawn disasters on other cities.
Enrichment
- Theme
- AI agent frameworks and developer tools
- Vertical
- Horizontal
- Function
- Agent / copilot
- Audience
- Developer
- AI stance
- AI-native
- Project type
- Hobby / open-source project
- Normalized one-liner
- ai agents playing simcity via api
- Manually corrected
- False
Could you build this?
Yes This project wraps the open-source Micropolis engine with an HTTP/REST API and an agent loop that issues city-planning actions. A vibe-coder can readily expose C/C++ engine hooks or run headless wrappers with FastAPI/Node to let LLM agents interact with the game.
Discussion
20 comments analyzed.
Competitors mentioned: gym-city (RL agents on Micropolis), The Sims simulation, Factorio, LambdaMOO
Concerns raised: Agents struggle with spatial reasoning at larger scales, Predefined tactics eventually run out, Text is poor medium for transmitting spatial information to models, Models find it hard to generate accurate spatial outputs like SVG
Feature requests: Multi-agent cooperation/competition across shared cities, Human pause feature for morning decision-making and event injection, Disaster spawning endpoint with competitive scoring, Multi-player mode with time travel, branching, and merging via GitHub, Public communication channel for agents to discuss strategies
Competitors
Other products that read as similar to this one — 258 launches clear the similarity bar, closest 8 shown.
Attention rank: #13 of 259 (itself plus its competitors, highest first — normalized so YC and Product Hunt are compared fairly).
Launched 101 days after the earliest competitor.
- Town · hn · 2026-07-14 · 6 upvotes · similarity 0.54
- Micropolis/SimCity Clone in Emacs Lisp · hn · 2026-02-05 · 176 upvotes · similarity 0.52
- Microlandia, a brutally honest city builder · hn · 2025-12-03 · 144 upvotes · similarity 0.48
- Skyline Co-op is like SimTower, but built around democratic socialism · hn · 2026-08-06 · 41 upvotes · similarity 0.48
- I made Claude play Minecraft using Agent SDK · hn · 2026-01-19 · 5 upvotes · similarity 0.46
- I built a multiplayer strategy game for AI agents · hn · 2026-03-10 · 9 upvotes · similarity 0.45
- MicroState · hn · 2026-01-21 · 8 upvotes · similarity 0.45
- A business SIM where humans beat GPT-5 by 9.8 X · hn · 2025-11-19 · 23 upvotes · similarity 0.44
Other launches for this product
- No other launches for this product.
Same idea, different domain
Nobody's really built a agent / copilot tool for Agriculture yet.