Uppy

Uppy is a co-op multiplayer browser game where a balloon is in the air, a bird tries to pop it, and the only way to keep the balloon up is to tap together. Each player has a short cooldown between taps, so coordination matters more than reflexes. The more people in your lobby, the harder it gets — and the higher your collective score can climb.

It's free, works on phones, and takes about ten seconds to join a game.

The Stack

The whole game runs on Cloudflare's edge platform. No traditional servers anywhere.

• Cloudflare Workers — single binary backend, no infrastructure to manage
• Durable Objects — per-lobby state. Each game room is its own DO with consistent state across every connected player, WebSocket fan-out built in
• D1 — cross-request persistence for auth, profiles, and scores
• Cloudflare Email Service — magic-link login emails
• Cloudflare Access — gates the dev environment
• R2 + Assets binding — static asset hosting from the same Worker
• PostHog — analytics and in-game feedback surveys
• Plain JavaScript on the client — no framework, no build step, single module

The whole thing deploys with wrangler deploy. Total infrastructure cost so far: free tier.

Why this stack

I wanted to learn Cloudflare's edge platform properly, and a real-time multiplayer game is one of the harder things you can build on it — if it works for a game with sub-100ms per-tick state sync across continents, it'll work for almost anything else. The constraints turned out to be the right ones: forcing every piece of state to live in either a Durable Object or D1 made the architecture obvious in a way that "stand up a server and put Redis next to it" doesn't.

What I learned

• Durable Objects are perfect for multiplayer state. Real-time sync across clients without needing Redis or Pub/Sub — the DO is the source of truth and WebSocket fan-out is built in. No glue code, no separate state service.
• The state management is the hard part. Not the WebSockets, not the rendering — the cooldown logic, the score reconciliation, the rejoin-after-disconnect edge cases. The kind of work that doesn't show up in a tutorial but eats your weekend.
• Playtesting with strangers is a different beast. Real human latency, real weird inputs, real "I clicked, nothing happened for 2 seconds, then 5 things happened" reports. Logs you can't reproduce in dev.
• The free tier goes further than you'd expect. A single Worker, a handful of Durable Objects, a D1 database, and the Email Service — none of it costs anything yet at the volume Uppy runs at.

Play it

uppygame.com — free, no passwords, drop your email once for a magic-link sign-in and you're in. Mobile-friendly. There's an in-game feedback prompt after each round; that's the fastest way to tell me what's broken or what would make it better.