This example presents a minimal React application that renders a styled circle to the screen. The code defines reusable components for a background circle, eyes, and a mouth, with the mouth’s path generated using the D3 `arc` function. The main `App` component initially displays only the text "Hello React!", while the additional components are prepared for future use. React and ReactDOM are loaded from CDN, and the visualization is mounted into a root div, demonstrating component composition and D3 integration for SVG shapes.