This example shows a minimal React application that renders the text “Hello React!” inside a web page. It demonstrates how to integrate React with a static HTML document, using external UMD builds of React and ReactDOM loaded from unpkg. The code defines a simple functional component, `App`, and mounts it to a root `div` element through `ReactDOM.render`. The page’s body is styled with zero margin and hidden overflow, while the bundled JavaScript file `bundle.js` supplies the application logic.