This example renders a full-screen smiley face using React and D3. It draws a yellow circle for the head, two smaller circles for eyes, and a curved mouth created with D3’s `arc` generator. The React component maps the SVG elements, while D3’s `arc()` computes the path for the mouth based on specified inner and outer radii and angles. All coordinates are dynamically calculated from the browser window size, and the SVG output scales to fill the viewport.