JetBrains/compose-multiplatform ? reverse-engineered prompt

Build me a simple Kotlin app that shares one UI across Android, iPhone, desktop, and the web.

I want a polished starter app that shows how to use a shared composable screen with a few basic features, like a home page, a list of items, an item details view, and a settings screen. Make it feel modern and responsive, with clean typography, good spacing, light and dark themes, and platform friendly navigation. If it makes sense, include a couple of native touches on each platform, like desktop menus, mobile style back handling, and a browser friendly layout for web.

Please keep the code organized so the shared UI is easy to reuse, and make it something I can run and extend without a lot of setup. If you need to check the latest Compose Multiplatform docs or APIs, look them up online first.