JellyBlob.win — Multiplayer Jelly Arena

Eat dew, trap rivals, go SUPERNOVA! 🌈

JellyBlob is a free multiplayer browser arena of wobbly, see-through gelatin jellies in a glowing night pond. No download, no account: open jellyblob.win and you're in a live pond with up to 150 players, on desktop or phone.

How it plays

• Eat dew to grow and paint a glossy goo trail
• Cut rivals off with your trail, hop over theirs and stomp smaller jellies
• Surge by shedding size for a burst of speed
• Fill your Glow to go Supernova: seven seconds of swallowing everything smaller than you
• Pond events every few minutes: Dew Storm, Prism Rain and a fleeing Golden Jelly

Dress up your jelly

137 collectibles (hats, eyes, trails, emotes, splat effects and 14 finishes like Gold, Chrome, Holo and Galaxy), 80 titles, a Reward Road to level 100 and beyond, daily quests and a weekly challenge with a leaderboard.

Under the hood

• Three.js refractive gelatin with spring-driven squash, stretch and slosh
• Authoritative 30 Hz Node.js server with client prediction, a gateway and one arena worker per CPU core
• Procedural music, liquid SFX and a soft ASMR narrator voiced by a local TTS model

How it was vibe coded

A from-scratch remake of the original JellyBlob, built in about ten days by prompting Claude Code (Opus 5.5) and Codex. The prompts described outcomes, not code: how clear the gelatin should look, how many players a pond must hold, which phones every control must work on. The agents wrote the game, the server, the tests and the release checks. Codex image generation painted the store art from real game renders.

Challenges we beat:

1. Real-looking gelatin on phones: screen-space refraction plus dynamic resolution and instanced jelly parts
2. Smooth crowded ponds: per-viewer delta snapshots, allocation-free encoding and load tests
3. One-screen phone UI in portrait and landscape, verified by automated launch checks that tap every touch control at its centre