This example creates a full-screen smiley face from geometric shapes using React. The face includes a yellow circular head with a black stroke, two eyes, and a blank space where a mouth would be, all positioned relative to the window dimensions. It renders SVG elements directly through React's JSX syntax, calculating coordinates and radii from `window.innerWidth` and `window.innerHeight`. The implementation uses React 16.9.0 and ReactDOM to mount the component into the page.