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doc/module.md

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+# Modules {#modules}
+
+FTXUI is organized into three modules, each building upon the previous:
+
+1. @subpage module-screen — low-level rendering
+2. @subpage module-dom — layout and composition
+3. @subpage module-component — user interaction
+
+---
+
+[ @subpage module-screen ]
+
+Defines:
+
+- **`ftxui::Screen`**: a 2D grid of styled characters.
+- **`ftxui::Pixel`**: the unit of rendering.
+- Helpers like `ftxui::Color` and `Dimension`.
+
+Use for direct terminal drawing and styling.
+
+---
+
+[ @subpage module-dom ]
+
+Provides:
+
+- **`ftxui::Element`**: a tree structure for layout and UI.
+- Composable and responsive elements.
+- `Render()` to draw onto a `Screen`.
+
+Ideal for structured, styled UIs.
+
+---
+
+[ @subpage module-component ]
+
+Adds:
+
+- **`ftxui::Component`**: stateful, interactive widgets.
+- Built-ins: `Checkbox`, `Input`, `Menu`, `Button`.
+- Supports keyboard/cursor input and composition.
+
+Use for interactive apps.
+
+---
+
+Modules can be used independently, or together: `screen → dom → component`.