A simple smiley face is rendered as an SVG inside a React component, with a yellow circular face, two black eyes, and a mouth shaped using D3's `arc` generator. The `BackgroundCircle` and `Eyes` components are reusable, receiving props for radius, stroke width, and eye offsets. The face is centered using an SVG `<g>` transform, and the arc’s inner and outer radii and angles define the mouth’s thickness and open shape.