This example renders a full-window smiley face using React and D3 v7. It shows a yellow face with black outline, two eyes, and a smiling arc, all positioned dynamically based on the browser viewport size. The code defines reusable React components like `FaceCircle`, `LeftEye`, `RightEye`, and `SmileArc`, with the latter using D3’s `arc()` generator to create the mouth path. SVG elements are drawn inside a `<g>` transform, and ReactDOM renders the composite face component into the page.