This example demonstrates a minimal React application that displays the text "Hello React!" centered on the page. The app renders a single message element using JSX syntax, with styling applied via a CSS class. The implementation uses React and ReactDOM from the production UMD builds, and the main component is defined in `index.js` where `ReactDOM.render` mounts the `App` component into the `#root` div. The page loads the React libraries from unpkg and uses a separate `bundle.js` for the application code.