Building Spinlings with Claude: shared game rules and the Desktop UI trap

Spinlings is a free, open-source creature game that operates within Claude Code, where pixel creatures battle above the prompt. Players can assemble a three-creature team, trade cards, and duel other players' saved teams. The game, originally built with Claude and refined with Codex, requires Claude Code 2.1.287+ and makes no AI calls or reads user prompts. It supports both online play, sending game actions to a server, and offline play with local saves.

Unlike other AI-powered games, Spinlings runs entirely within Claude Code, making no AI calls and never reading user prompts or project files.