#Build a game for OGS

OGS (Open Game System) puts web games on the living-room TV. A grown-up casts once from the OGS app; after that the TV shows one page all evening, the TV launcher, and every game plays inside it. Phones and iPads join the couch and play each game's phone page. Your game stays an ordinary web game: it gets a few postMessages and a small library, and it keeps working in a plain browser.

Building with a coding agent? Point it at the Quickstart or at https://ogs-docs.pages.dev/llms.txt. Every page here is also plain Markdown: add .md to its URL.

#How an evening works

1. Cast once. The host opens the OGS app and casts to the TV (Chromecast, or any browser on the TV). The TV shows the launcher and a 6-character TV code.
2. Phones join the couch. Everyone else joins with the TV code. Each person has an OGS profile: a name and an avatar.
3. The launcher frames your game. When someone picks your game, the launcher loads your TV page in an iframe and tells it who is on the couch. Swapping games never recasts.
4. Phones open your phone page. The app opens your game's startUrl in a WebView. Your page asks profile-kit who is playing and skips its own name form.
5. Home parks your game. When the couch goes Home or switches games, the launcher keeps your frame loaded but parked, and tells you to go silent. Continue brings the same frame back instantly.

#Your two pages

A game with one static TV page lists it as tvUrl in its manifest. A room-based game (each room has its own TV URL) declares the room's TV page from the phone page at runtime. Either way the game never casts: OGS does.

#What your game gets

• Who's playing. On the phone: the player's OGS name, avatar and a game token. On the TV: the whole couch (players) and a game token for the session. No sign-up, no name form.
• Verified identity. Game tokens are ES256 JWTs signed by OGS for your game only (aud = your appId). Your server checks them with one call, verifyOgsToken.
• Sitting labels. Report "Mission 6" or "Room KQTP" and the OGS app shows it in Playing, so two sittings of your game read apart.
• Pause and resume. A clear signal when the TV parks your game and when it comes back, so you can stop the music and keep state.
• Casting handled. No cast SDK, no cast button, no receiver app, no join codes on the TV.
• Several couches in one room (optional, multiCouch): households in different homes play one room of your game.

#What OGS asks of you

The short version of the rules:

• No cast button and no room code or join QR on an OGS TV.
• Nothing covers the TV's focal area; stay inside the safe area.
• Silent while parked.
• Still playable in a plain browser, where every profile-kit call returns null or does nothing.

#Where to go next

• Quickstart for agents: the step-by-step checklist.
• The game contract: the single source of truth.
• profile-kit reference and Messages and manifest: exact APIs.
• Testing your game, Art kit and catalogue.