This example renders a full-screen yellow smiley face using React and D3.js. The face is centered with a circular head, two eyes offset horizontally and vertically, and a mouth drawn as an arc path using D3’s `arc` function. The SVG coordinates adapt to the browser window’s inner dimensions, and the face scales based on the viewport height. The implementation relies on React’s `ReactDOM.render` to mount the SVG, while D3 supplies the arc path for the mouth.