A React-based smiley face visualization renders a full-screen SVG face using D3’s arc generator for the mouth. The face is centered with a yellow circle, two black eye circles, and a thick stroke outline, all sized dynamically to the window dimensions. The code imports `arc` from D3 and computes positions for eyes and mouth using constants for offsets and radii. React’s `ReactDOM.render` mounts the SVG into the DOM, while the `<path>` element for the mouth is constructed via `mouthArc()`. The example demonstrates combining React components with D3 geometry primitives for static, responsive graphics.