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A live demo of TypeSafe's Jev model playing Flappy Bird, one flap-or-wait decision at a time.
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CommunityJev Demos & Experiments
Jev Plays Flappy Bird
Live demo of Jev playing Flappy Bird: about twenty times a second the game asks one question, flap or wait, and applies Jev's choice exactly as returned — no thresholds, no backup rules, no retries.
- Stars
- 4
- Language
- TypeScript
- License
- MIT
- Reading time
- 3 min
- Published by
- Community
- Author
- hosseintoussi
- Last verified
- Oct 2026
Used inJev for Gaming
- Languages
- TypeScript
- Platforms
- Browser
- Capabilities
- Open sourceRequires API key
Highlights
- The game asks Jev one multiple-choice question about twenty times a second: FLAP or WAIT, each option with a short description of when it applies.
- The snapshot describes the scene — bird position and speed, pipe gap, clearance, words like 'inside the gap, lower half' — and never tells Jev what to do.
- Answers are applied exactly as returned: no thresholds, no backup rules, no retries; a retried answer would arrive too late to be useful.
- The game never waits, asking a new question every 50ms with about six in the air; answers superseded by a flap are discarded and logged.
- Your TypeSafe API key stays on the local server in server/jev.ts, is never sent to the browser, and .env is git-ignored.
Quickstart
bash
npm install
cp .env.example .env
npm run devWatch out
Copy reviewed against the repo README on 2026-10-15; the captured README was truncated mid-paragraph about the single response stream. The 'ten times fewer deaths' figure comes from the author's simulation of latency-lead handling, not an independent benchmark, and returned latency depends on your network.
Questions about this entry
Short answers drawn from the linked project or page.
About twenty times a second the game asks Jev one question: flap or wait. Each option has a short description of when it applies, the question lives in src/question.ts, and the bird does what Jev answers — nothing else controls it. If Jev stops answering, the bird falls.
A small snapshot: where the bird is and how fast it is moving, how far away the next pipe is and where its gap starts and ends, the room above and below, and the same facts in plain words like 'inside the gap, lower half' or 'falling'. It never tells Jev what to do.
An answer slower than JEV_TIMEOUT_MS counts as an error; the default timeout is 2000 ms and Jev itself needs about 100 ms, with the rest being network. The game never waits: it keeps running and asks the next question without waiting for the last answer. If Jev stops answering, the bird falls.
The game asks a new question every 50ms and does not wait for earlier answers. A WAIT changes nothing, but a FLAP changes the bird's path, so questions asked before that flap described a bird that was left alone and their answers are discarded and logged as superseded. This is a freshness check, not a flap rule.
You need Node 20 or newer and a TypeSafe API key. Run npm install, copy .env.example to .env and paste your key from console.typesafe.ai/keys, then npm run dev and open http://localhost:5173. Press Space to start.
The README says your API key stays on the local server in server/jev.ts and is never sent to the browser, and .env is git-ignored. Settings in .env include TYPESAFE_API_KEY, TYPESAFE_DEFAULT_MODEL, which defaults to jev-latest, and JEV_TIMEOUT_MS.
Yes. TYPESAFE_DEFAULT_MODEL defaults to jev-latest, and the README says you can pin a version like jev-1.13.0 for repeatable runs. JEV_TIMEOUT_MS defaults to 2000 and defines how long an answer may take before it counts as an error.
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