A React-rendered SVG smiley face adapts to the browser window, sizing its yellow circular head and black features relative to the viewport dimensions. Using React 16.9 and ReactDOM, the code computes the center coordinates, stroke width, eye offsets, and mouth radius from `window.innerWidth` and `window.innerHeight`, then renders a `<svg>` with a transformed `<g>` group containing positioned circles for the face and eyes, leaving the mouth partially specified.