Rune is a cross-platform music player and library manager built with a Rust backend and Flutter frontend. It provides local audio playback, metadata extraction, audio analysis (FFT, spectral features, MFCC, chroma), acoustic fingerprinting (MusicBrainz/Shazam-style), and a recommendation engine based on feature vectors. The system supports multi-device synchronization using Hybrid Logical Clocks (HLC) and chunked data transfer, LAN device discovery with TLS certificate pinning, and scrobbling to Last.fm, Libre.fm, and ListenBrainz. It includes a CLI tool, a Svelte-based authorization panel for remote server management, and a full GUI with cover art wall, lyrics display, dynamic mixes, and extensive theming. Architecturally, the project is a monorepo with 11 Rust crates and a Flutter app. The Rust backend (native/hub) handles database operations (SeaORM/SQLite), audio analysis, playback (rodio), networking (WebSocket/HTTP server), and sync. The Flutter frontend communicates via rinf (Rust-FFI message passing). The codebase demonstrates strong engineering practices: trait-based abstractions (FsIo, PlaybackStrategy, HLCRecord), macro-driven boilerplate reduction (collection_query!, parallel_media_files_processing!), and a clean separation of concerns between UI, business logic, and data layers. While primarily an application, it incorporates significant data engineering patterns in its sync and analysis subsystems, making it a hybrid project with reusable data infrastructure.