Update README.md

Author: Geolm

README.md

@@ -1 +1,65 @@
-# leanUI
+# LeanUI
+
+LeanUI is a small immediate-mode UI library written in C99.  
+It’s designed for games and lightweight applications that need a clean, polished interface without bringing in a full framework.
+
+![LeanUI demo](docs/leanui_demo.gif)
+
+---
+
+## Overview
+
+- Immediate-mode API  
+- No allocations, no dependencies beyond the C standard library  
+- Single header / single source, easy to drop into any project  
+- Built-in easing and animation for a smooth, modern feel  
+- A focused set of well-designed widgets  
+- ~500 lines of code, compiles in seconds
+
+LeanUI aims to sit between *microui’s minimalism* and *modern UI polish*.  
+It’s not a giant toolkit, but it’s not barebones either.
+
+---
+
+## Widgets
+
+LeanUI provides a small, cohesive set of widgets:
+
+- **Buttons** — with hover and press animations  
+- **Labels / value fields** — for clean key–value layouts  
+- **Toggles** — animated switches inspired by iOS  
+- **Segmented controls** — for mode switching  
+
+Each widget is built with consistent spacing, alignment, and interaction patterns.  
+The goal is not to cover everything, but to make a minimal set look and feel right out of the box.
+
+---
+
+## Animation & Easing
+
+Unlike most tiny immediate-mode UI libraries, LeanUI has animation built in:
+
+- Hover, press, and toggle states are automatically eased over time.  
+- New windows and panels animate smoothly when they appear.  
+- No per-widget state is stored — transitions are computed implicitly based on widget identity.  
+- Common easing functions (e.g. quadratic, overshoot) are included.
+
+This gives small UIs a fluid, modern feel without adding complexity to your code.
+
+---
+
+## Example
+
+```c
+#include "lean_ui.h"
+
+void frame(void)
+{
+    ui_begin();
+
+    if (ui_button("Click Me")) {
+        // Handle button press
+    }
+
+    ui_end();
+}