Windows 11 Design for Reactor

Author, review, and fix Reactor UI code following Windows 11 design system rules.

Reactor is a functional UI framework for WinUI 3 that builds UI entirely in C# — no XAML, no data binding, no ViewModels. UI is described with immutable Element records, composed via bare factory methods imported with using static Microsoft.UI.Reactor.Factories (TextBlock(...), VStack(...), etc.), and updated through a React-style reconciler with hooks (UseState, UseEffect, etc.).

Controlled prop note: when design examples use inputs such as TextBox(value, setValue) or Slider(value, ...), the factory keeps the simple call-site shape. Direct element-record reads of controlled props now return Optional<T>; use .GetValueOrDefault(...) or .Value. See migration/050-optional-t.md.

This skill translates the Windows 11 design language into Reactor's C# projection so that apps built with Reactor look, feel, and behave like first-class Windows 11 applications.

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