This example demonstrates a minimal React application that renders a simple "Hello React" message on a blank page. It combines React 18 with D3 v7 by loading both libraries via CDN. The code defines a D3 arc generator for a mouth shape, but the visible output is only the static text. ReactDOM renders the App component into a root div element, while the page’s global styles hide any default margins and overflow. The example serves as a foundational template for integrating React and D3 in a single-file setup.