This example renders a yellow smiley face that fills the browser window, with two eye circles and an invisible mouth, using React to define the SVG structure. The face is centered via a `<g>` transform, and its size adapts to `window.innerWidth` and `window.innerHeight`. The code uses React 16.9 and ReactDOM to mount the component into a root div, with SVG circle elements positioned by computed offsets for the eyes and stroke width for the face outline.