hoffstadt/DearPyGui ? reverse-engineered prompt

Build me a fast, polished Python GUI toolkit that feels modern and runs on Windows, macOS, and Linux.

I want the app to have the same vibe as Dear PyGui, with a clean built in demo window, a few basic widgets like text, buttons, inputs, sliders, and a place to show plots and node style interfaces. It should feel snappy, use very little setup, and be easy to import and use from a simple Python script. Please make the default experience look good out of the box, but still let me change themes and styles easily.

If there are any platform specific details or current docs I should follow, look them up online while you build it. Also include a simple example script and make sure the demo can be launched quickly so I can see everything working right away.