This example renders a responsive smiley face using React and D3 inside an SVG canvas. It uses the `d3.arc` API—though the face itself is assembled from simple SVG circles—with eye, mouth, and head geometry computed from window dimensions. The `App` component dynamically sets the SVG width and height to fill the browser viewport, centering all elements via a `transform` translation. The code explicitly imports `arc` from D3 but does not actually invoke it, instead relying on React's declarative JSX for all drawing.