Game

New York — AI-Looping Open-World Multiplayer Game

Matt Shumer

@mattshumer_ · 396.6K followers

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Sep 23, 2026

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An open-world NYC browser game where Claude Opus 5.5 has been running autonomously in a loop for nearly a day, continuously writing and improving its own code. You enter as a named character, spawn on a real NYC block, and share the city with other live players. The mobile view reveals a 3D street scene with pedestrian characters and yellow cabs. Matt Shumer (@mattshumer_) built it and let the model iterate on its own — the game keeps getting better without him touching it.

Claude Opus 5.5 loops autonomously, rewriting the game's code continuously for 24+ hours with no human intervention
Fully multiplayer — other players appear in the city in real time, each with a randomized handle like amber-fox-42
"Spawn at your block" feature ties your real NYC address to your in-game location

“Opus 5.5 has been looping on my open-world NYC game for almost a day now, and it's continuing to improve. Jump in and try it (it's multiplayer!): https://somethingbig.ai/world/”
— @mattshumer_

browser-game multiplayer open-world autonomous-ai nyc claude-opus dark-mode bold-typography 3d