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Play Rex Mundi in your browser

It does not run on a phone: most phones cannot draw its map yet. Send this page to the computer you will play on, or type rexmundi.alexisbouchez.com/play into its browser.

Send me the link

Every game here is solo: the game master built into Rex Mundi plays the rest of the world, and no agent is needed. Click the map before you use the keys: Escape opens the menu, and New game starts one. You can also open the game on a page of its own.

What it needs

A browser that draws with WebGPU, on a computer: Chrome or Edge, or Firefox 141 and later. The first visit fetches about 38 MB, the map and the game.

Your games are kept in this browser, on this computer only. Clearing the site's data clears them, and a long game can outgrow the room a browser gives a site. The download keeps every game on disk.

With your own agent

Every clip of Rex Mundi is a real game, played on a computer by a person and their coding agent, which writes each turn as the game master. That takes the download: it is free, and runs on Windows, macOS and Linux. Three steps from a clip to a game of your own:

1. Download it

Pick your system:

2. Open it

  • On Windows, run the installer. Windows warns about a publisher it does not know: choose More info, then Run anyway.
  • On a Mac, the terminal line installs it and opens it.
  • On Linux, make the AppImage executable and run it.

Then pick the agent that will write your turns: Escape opens the menu, then Settings, then Game master. Claude Code, Codex, OpenCode, Mistral Vibe and Pi are there. If it will not start, the troubleshooting page has the fix.

3. Open the game from the clip

A clip that shares its game links to it: a watch page whose address ends in #timeline= and the address of a .rexmundi file. Open the link on the computer to watch the game in the browser. To play on from where it stopped, download the file at the address after #timeline= and drop it on the game's window, or choose it under Load game, then Import. It opens as a game of your own.

A clip with no link is a game you can start yourself: New game, then click the country it showed.