This example displays a large, centered “Hello React!” message in a web page. It demonstrates the basic setup of a React application using React 18 and ReactDOM’s `createRoot` method. The code imports `React` and `createRoot`, defines a simple functional component that renders a styled `div`, and mounts it to the root element. The HTML loads React and ReactDOM from a CDN, with the app’s TypeScript code compiled into `bundle.js`.