Otter Music is a cross-platform music player application that aggregates multiple music sources (NetEase, QQ Music, Kuwo, Kugou, Migu, Bilibili, etc.) into a unified interface. It features music search, playback, playlist/favorites management, lyrics display, sleep timer, offline downloading, and cross-device synchronization via Cloudflare KV. The architecture combines a React/Vite frontend with Zustand state management, a Cloudflare Workers/Hono backend for API proxying and sync, and Capacitor for native Android integration. Key entry points include src/main.tsx (frontend root), functions/app.ts (backend), and android/app/src/main/java/com/otterhub/music/MainActivity.java (native). Data flows involve unified music API calls to platform-specific providers, audio URL resolution with caching, encrypted IndexedDB persistence for user state, and sync via Cloudflare KV. External dependencies include numerous music APIs, Capacitor, React, Zustand, Tailwind CSS, and Radix UI primitives.