tl;dr: MicroUI is a ~1100 SLOC ANSI C immediate-mode UI library that operates within a fixed-size memory region with no additional allocations. It provides standard controls (windows, buttons, sliders, textboxes, etc.) and a simple layout system, but doesn't render anything itself—users supply input and handle the emitted draw commands, making it compatible with any renderer capable of drawing rectangles and text. The project is intentionally minimal, so feature-additions PRs likely won't be merged, though it's designed for easy extension with custom controls.