React renders a full-screen SVG smiley face with a yellow circle head, black stroke, two eyes, and an arc-based mouth. The component computes dimensions from window.innerWidth and innerHeight, centering the face dynamically. D3’s `arc()` helper generates the mouth path with specified inner/outer radii and angular range, while `ReactDOM.render` mounts the SVG directly into the DOM. No external data is loaded; all geometry uses static constants for offsets and radii.