This example renders a full-screen smiley face using React and SVG. The face is built from three circles: a yellow head with a black stroke, and two black eyes positioned symmetrically around the center. The head’s radius is calculated from the window height, and the eyes are offset from the center using fixed x and y distances. The code uses React’s `ReactDOM.render` to mount the SVG into a root element, with the viewport dimensions set from `window.innerWidth` and `window.innerHeight`.