A React-rendered SVG smiley face fills the browser window, with the face radius tied to the viewport height and centered via a translated group. The yellow circle, black stroke, and two offset eye circles are positioned using inline numeric constants for eye offset and radius. The example demonstrates reusable SVG elements composed through JSX, leveraging React and ReactDOM for declarative rendering. The window dimensions are read directly to size the graphic, and the mouth mentioned in the title is not present in the rendered output.