Druid is a cross-platform, data-driven GUI toolkit for Rust, providing a reactive widget system with immutable state management via the `Data` trait and composable `Lens` for data access. It supports multiple backends (macOS, Windows, GTK, X11, Wayland, WebAssembly) through a platform abstraction layer (`druid-shell`). The framework includes a rich set of built-in widgets (Flex, Scroll, Split, TextBox, etc.), a layout system inspired by Flutter's `BoxConstraints`, an environment-based theming system (`Env`), and a command/notification system for inter-widget communication. The project is explicitly discontinued and unmaintained, with its successor being Xilem. Despite this, the codebase exhibits high craftsmanship with clean abstractions, well-documented patterns (Controller, Scope, Lens combinators), and a modular architecture that influenced later Rust UI frameworks. However, technical drift is high due to outdated dependencies, incomplete backend implementations (especially Wayland and Web), and deprecated API usage.