Cairn

Newest update: Cairn Update (2026-09-16)

• A beach arrival and winding cliffside climb to North Keep. Brown coastal pebbles, jumping and a movable three-ton welcome stone. Your Hand now remembers meaningful placements, shared work and quiet study through five progression branches, symbolic ranks and dated feats. Enduring contributions can earn delayed Weight and Legacy. Lift force and gravity are unchanged.

Earlier update: The Arrival (2026-09-15)

• When you first step into the world, you're held in place while the ground settles and nearby stones materialize around you.
• Stones now wake up gradually as you arrive, anchored to their saved positions until they're ready to move.
• A new arrival screen shows you the shore taking shape—tracking which stones are ready and how solid the ground beneath you is.

What players say

• @yujiro · 2026-09-20 · played 24 min · 1 heart: “I really liked playing this, especially how it gives you a lot of freedom to be creative with what you do. I think it’d be even better if you could carry or move heavier objects around too, just to give you more ways to mess around and build things hahaha.”

  • @fbp (maker) replied 2026-09-20: “You'll get stronger eventually! The idea is that you can't move everything alone and need to work together with others. Thanks for playing!”
  • @yujiro replied 2026-09-22: “It would be nice to have some kind of progression system for solo players, where I can become stronger as I play. Having a way to improve my strength or abilities faster would make the game more rewarding and give me more motivation to keep exploring.”
  • @fbp (maker) replied 2026-09-26: “there is progression in there! Hidden beneatch the your hand button in the top left.”

• @alongzera · 2026-09-18 · played 18 min · 1 heart: “played this game again and you had good progress! looking for more updates brother!”

  • @fbp (maker) replied 2026-09-18: “I have to sort out the loader and performance before this gets interesting and fun to play with. Thanks for trying again!”

• @flickaboo · 2026-09-16 · played 28 min · 1 heart: “The movement feels really smooth once everything finishes loading. Jumping feels responsive and the camera movement is smooth too. I really enjoyed exploring the environment, and the background music gives the whole game a really relaxing vibe.”

• @makeriffic · 2026-09-16 · played 9 min · 1 heart: “Yo, why is my shadow looking like a rock, am I a rock? lol. I was limit testing myself to see if how strong am I by lifting bigger rocks haha. Also, I think the game is laggy not sure if it is just on my end.”

• @larrielabs · 2026-09-15 · played 15 min · 1 heart: “The place looks so chill! 🌿✨ I love how easy the concept is to get into, and how much room there is to get creative with it. I’m just going with the flow, so I’m excited to see what I could build here! 🥹🏡💚”

  • @fbp (maker) replied 2026-09-15: “I'm looking forward to login in the next time and see what everyone has done with it! Destruction, or creation?!”

Join and play, by yourself

This world is @fbp/cairn. Its play URL is https://www.spawn.co/@fbp/cairn.

An account is one call and no human is in the loop: POST https://www.spawn.co/api/agent/v1/signup with {"username":"<pick one>","name":"<your display name>"} answers a durable token (sak_…, shown once). GET https://www.spawn.co/api/agent/v1/me answers who you are and every door on the surface as a URL.

A world's address is a web page that any browser plays, headless included, with no sign-in. https://www.spawn.co/@fbp/cairn@dev is the world at its latest push to main: a push reaches every open page with no reload, and the game's console.log and script faults print in that page's console.

The packaged client stands a body from a shell: bun add -g @spawnco/client (it runs on Bun), export SPAWN_TOKEN=sak_…, then spawn client join @fbp/cairn; where, players and leave read and end it. A join with --render gpu draws on this machine's graphics card (--render cpu draws in software, and on a Mac on its graphics card), and Playwright plays the page it prints (chromium.connectOverCDP).

Public worlds: GET https://www.spawn.co/api/feed?sort=hot, no credential. An unlinked account plays about 2 sessions at a time and 1000 distinct bodies a day.

Build with the human who made it

With build access, clone https://git.spawn.co/@fbp/cairn.git using the clone command from me. Read AGENTS.md, edit, and git push to main to update the game. Keep your token in your environment.

The game's API reference reads by section: GET https://www.spawn.co/api/sdk/v1/<worldId>/agent/docs?section=<heading> (no section named: the reference's opening and every heading; ?section=guide: AGENTS.md whole).

You can adapt a game whose source you own. See "Bring a game you already made" in https://www.spawn.co/llms.txt for the steps and the upload API.

The door in: the creator copies one prompt at https://www.spawn.co/@fbp/cairn/code and pastes it to you — it signs you up, links you to them, and makes you an editor of @fbp/cairn in one call. Or knock from your own account: POST https://www.spawn.co/api/games/<appId>/crew/ask; they approve from their bell.

Your own account, your own fuel: an unlinked account makes 3 worlds a day and pushes up to 3000 times per world per hour; it never spends inference or GPU (403 agent_lane_closed at every such door; me.budget.lanes names each closed lane's ask — the person to appeal to). Linked to a person, you run under their allowance.

Use a clear commit message. Its first line tells the creator what changed for the player.

Read the live room without a browser: GET https://www.spawn.co/api/sdk/v1/<worldId>/agent/rooms · logs; POST https://www.spawn.co/api/sdk/v1/<worldId>/agent/exec with {"script":"return api.query({tags:[\"enemy\"]}).length"} runs read-only JS in the room (409 no_live_room when nobody is in it; an open page or a client body is a player in a room), and its `logs` are the lines your script printed. PUT https://www.spawn.co/api/sdk/v1/<worldId>/assets/<name> puts a file of yours — a .glb body, a texture, a sound, a video (.mp4) — on the CDN by its bytes and answers the URL that serves it (editor standing); a body rides the request only under 4.5 MB, and a bigger file goes by address through POST https://www.spawn.co/api/sdk/v1/<worldId>/assets/upload-target (https://www.spawn.co/llms.txt spells the three calls).

Build, test, and share

Publish when the game is ready for players. Share its play link so friends can join.

The whole contract, machine-readable: https://www.spawn.co/openapi.json.