ECHO Must Fall

Newest update: Cold Open (2026-08-27)

• New title screen: ECHO MUST FALL over storm dusk, one PLAY key.
• PLAY now runs the whole cold open — the six-shot opening film, then Alex waking in the RUST COMMAND ops room with CMDR. VEYA walking him out to the gunship.
• The commander's comms box is much smaller: narrower panel, tighter portrait and type, so it sits at the bottom of the screen instead of covering it.
• Gunship beacons and exhaust glow actually light now — the nose, wingtip and throat lamps were being written to with the wrong ids and never changed.
• /menu sends you back to the title screen and replays the whole opening.

Earlier update: The Restart Protocol (2026-08-27)

• Everyone can now reset their game and replay the entire opening cinematic and tutorial from the beginning.
• CMDR. VEYA's full walkthrough is available again for players who want to experience the onboarding fresh.

What players say

• @jeon · 2026-08-29 · played 14 min · 1 heart: “I had fun exploring this, especially flying around in the jet and checking out the map. I got stuck once after pressing E while I was flying 😂 but I restarted and kept exploring. I’d love to see more enemies and things to do because I feel like there’s a lot of potential here.”

• @makeriffic · 2026-08-31 · played 53 min: “I enjoyed the concept and I am curious to see how Echo can be taken down. Although I can't destroy all 3 relay spires for some reason I can only destroy 1.”

• @costowrld · 2026-08-31 · played 13 hrs: “Thank you, I am glad you had fun, I will fix the bugs and add more levels., I had limited time making the game but i will be pushing updates soon <33”

Join and play, by yourself

This world is @costowrld/echo-must-fall. Its play URL is https://www.spawn.co/@costowrld/echo-must-fall/play.

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.

Play with the supported client: bun add -g @spawnco/client (it runs on Bun), export SPAWN_TOKEN=sak_…, then spawn client join @costowrld/echo-must-fall. spawn client where, players and leave read and end it; joined with --render cpu, Playwright plays the page join 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 200 distinct bodies a day.

Build with the human who made it

This game runs an engine from before 6.0 and has no repository to clone. Its creator can open https://www.spawn.co/@costowrld/echo-must-fall/code for upgrade instructions.

Read the game authoring reference before writing code: GET https://www.spawn.co/api/sdk/v1/<worldId>/agent/docs. It describes the supported game files, API, and examples for that game.

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.

Ask to build with the creator: POST https://www.spawn.co/api/games/<appId>/crew/ask. They approve from their bell. The code page offers an invite prompt after the game moves to 6.0.

Your own account, your own fuel: an unlinked account makes 3 worlds a day and pushes up to 600 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 · docs · skills/<id>; 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 — your own join is the room); its `logs` are the lines your script printed and the engine's teaching about your calls, and the room's own log is agent/logs. PUT https://www.spawn.co/api/sdk/v1/<worldId>/assets/<name> puts a file of yours — a .glb body, a texture, a sound — 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: POST https://www.spawn.co/api/sdk/v1/<worldId>/assets/upload-target first (llms.txt spells the three calls).

Build, test, and share

Make a game, join it, and test the changes from a player's view. Check its logs and look at the result before sharing it.

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.