This example renders a full-screen smiley face using React and D3’s `arc` generator for the mouth. The SVG circles form the yellow face, black stroke, and eyes, while the mouth path is created via `arc()` with specified inner and outer radii and angled start/end points. Position and size are computed from the browser window dimensions, and the face is centered with a D3 `g` transform. The code uses React for component structure and `ReactDOM.render` to mount the SVG, with all coordinates and styling defined in JavaScript.