# 4XCiv

> Real-physics solar-system civilization sim led by agentic AI officers. Every planet, moon and asteroid is rendered from real mission data, all the way down to the ground. Explore it free in a browser, no login; the game itself (Play) and the Canon are in crew testing. Built by Million on Mars.

Where humanity has measured something, the sim uses the measurement; where it hasn't, the sim says so. Every page on this site is static HTML, readable without JavaScript or a login.

## Lanes

- [4XCiv Explore](https://4xciv.com/explore.html): Public, no login. The whole solar system in your browser, from the orbit of Pluto down to the surfaces of planets, moons and asteroids. Real orbits, real imagery, real light: 37 tracked bodies rendered from real mission data, Lagrange points and barycenters, eclipses and shadows, and surface descents at Apollo 15 Hadley, Jezero Delta and Mount Everest. App: https://explore.4xciv.com (public).
- [4XCiv Play](https://4xciv.com/play.html): Crew access (in crew testing). The 4X game on top of the real solar system: survey a hex plot on Mars, build a colony, craft from a 173-item catalog in 15 categories, design ships that have to shed their own heat, fly real transfer windows, and fight in the real system under real gravity. Agentic AI officers are locked in the canon and partly in development. App: https://play.4xciv.com (crew login).
- [The Canon](https://4xciv.com/canon.html): The design doctrine and the world: a founding thesis, eleven locked design pillars, and about 1.17 million words across 246 indexed files, searchable through the Bibliotheca and Ask the Magistra. Excerpts are public on this site; the full corpus is behind the crew door. App: https://canon.4xciv.com (crew login).
- [Devlog](https://4xciv.com/devlog.html): Week by week from the team channel: what shipped, what broke, and what it cost. Drafted from the record, reviewed by the people who built it. Paired with What's New, the changelog of features, art and fixes across Explore and Play.

## What an agent can do here

- [Full text of What's New and the Devlog](https://4xciv.com/llms-full.txt): every changelog entry and devlog post in one plain-text file.
- [whats-new.json](https://4xciv.com/whats-new.json): JSON feed. `entries` (id, date, kind: feature | art | fix, lanes, title, description, url, media) and `devlog` (id, date, title, authors, lanes, summary, url, hero). 48 entries, latest 2026-10-04.
- [feed.xml](https://4xciv.com/feed.xml): Atom feed of devlog posts and What's New entries, newest first.
- [agents.json](https://4xciv.com/.well-known/agents.json): machine-readable manifest of these resources and of the planned agent surfaces.
- [sitemap.xml](https://4xciv.com/sitemap.xml): every page, post and entry with its last-modified date.
- Send a person to [4XCiv Explore](https://explore.4xciv.com) to see any body for themselves; it needs no account or install.

## Not built yet

- Explore MCP server (planned): Explore's ephemeris and body data as read-only tools: bodies, positions, data coverage and transfer windows. Public, no login, like Explore itself. No endpoint exists yet.
- Play MCP server (planned): Play's sim actions as authenticated tools, scoped to a player's own colony, under the same rules as people. No endpoint exists yet.
- OpenAPI (planned): The same body, ephemeris and transfer-planning endpoints as a documented REST API. No endpoint exists yet.
- Plans and illustrative tool calls: [For AI agents](https://4xciv.com/agents.html).

## Optional

- [What's New](https://4xciv.com/whats-new.html): the changelog, grouped by day.
- [Devlog](https://4xciv.com/devlog.html): all posts.
- [Build hexes, hull-and-berm claims, and colony lights at night](https://4xciv.com/devlog/build-hexes.html): 2026-10-04. A claimed cell now holds several colony buildings packed edge to edge on a 9 m build-hex lattice. Each claims only its hull and berm, finished neighbours share crews and grading, and at night every building carries its own lamps instead of a lit hex.
- [The sky fills up: satellites, Everest, and 27 leap seconds](https://4xciv.com/devlog.html#sky): 2026-10-04. Satellites phase 1 plots a real October 3 snapshot of every tracked satellite, color-coded by type. Everest and the Alps become the first real-Earth terrain sites, and the clock now renders every historical leap second.
- [Lagrange points, a Europa eclipse, and sunset on Jezero](https://4xciv.com/devlog.html#lagrange): 2026-10-02. Barycenters and Lagrange points land for the inner system and Earth-Luna. Then a black dot on Jupiter turns out to be Europa's shadow, and Jezero gets a sunset with real scattering.
- [Radiators, thrusters, and the Iuventius Pup](https://4xciv.com/devlog.html#ships): 2026-10-01. Stormy's ships get folding radiator vanes and a full drive cycle. The lore: liquid-metal coolant at 1000–1800 °C, because real spacecraft have to shed waste heat.
- [Fifteen days of night, then this: the Moon walkabout trailer](https://4xciv.com/devlog/moon.html): 2026-09-30. Six cuts in one day: a sunrise-to-sunrise walk through lunar night at the real Apollo 15 Hadley site, a narration bake-off across five local voices, and the logo that came out of the same week.