A dynamic smiley face fills the browser window, rendered as a single SVG using React. The face’s yellow circle, black stroke, two eyes, and an arc-based mouth are drawn with React elements, while D3’s `arc` generator computes the mouth’s curved path. Coordinates adapt to `window.innerWidth` and `innerHeight`, centering the face and scaling its radius based on viewport height. The code combines React’s component model with D3’s geometry helpers within a plain SVG output.