Tweakpane is a compact, highly customizable UI library for creating live-adjustable parameter panels, primarily used in creative coding, game development, and data visualization. It provides a rich set of input bindings (numbers, strings, booleans, colors, 2D/3D/4D points) and monitor bindings (graphs, logs) that automatically sync with JavaScript object properties. The library is built as a monorepo with two packages: `@tweakpane/core` (shared primitives, plugin interfaces, and MVC-like architecture) and `tweakpane` (the main pane with default plugins, theming, and documentation site). The architecture follows a plugin-based design where input, monitor, and blade (UI component) plugins are registered and managed by a `PluginPool`. Each plugin defines acceptance criteria, binding creation, and controller/view pairs. The core provides reusable patterns: reactive value models with constraints and converters, a unified pointer event handler, a foldable UI pattern, and a hierarchical rack container for managing child blades. Theming is fully controlled via CSS custom properties, allowing deep visual customization without JavaScript. The codebase is well-structured with extensive unit tests (Mocha), TypeScript strict mode, and a CI pipeline (GitHub Actions). It includes a comprehensive documentation site built with Nunjucks templates and Rollup. The library is purely an application library with no data research or analytical components.