smiley face
This example renders a yellow smiley face from modular React components, combining a background circle, two eyes, and a mouth arc. The face is assembled using SVG circles and a path generated by the `d3.arc()` API, with the mouth’s shape determined by inner and outer radii and start/end angles. The `Face` component composes separate `BackgroundCircle`, `Eyes`, and `Mouth` subcomponents, all positioned via a centered `<g>` transform within an SVG container. D3 v7 provides the arc generator, while React manages the component hierarchy and props for sizing, offsets, and stroke widths.