This example displays a full-page, centered "Hello React!" message rendered as oversized text. It uses React 16.13.1 via the UMD production builds of `react` and `react-dom`, with `ReactDOM.render` mounting a functional `App` component into a `#root` div. The styling is minimal, applying a 13em font size through a `.message` CSS class defined in the inline `<style>` block. No data or interactive behavior is present beyond the static text output.