Naellx/Dummy-ui ? reverse-engineered prompt

Build me a simple Lua UI library that I can drop into a project and use to make basic menus and panels.

I want it to feel easy to use, with a clean example script that shows how to create a window, buttons, labels, input fields, and toggles. It should be straightforward to customize colors, size, and text, and it should be organized so I can understand and extend it later.

If anything is unclear, please look up the current docs online or make sensible choices that fit a lightweight Lua UI toolkit. Also include a small demo so I can see how it works right away, and make sure the code is tidy enough that I can reuse it in other Lua projects.