This example renders a classic smiley face as a yellow circle with black outlines, two eyes, and a curved mouth, composed entirely of SVG shapes. The face is centered within an 960x500 viewport, with a background circle from `BackgroundCircle`, circular eyes from `Eyes`, and a mouth generated using D3's `arc` constructor to create an arc path. The React app uses ES6 named exports, and D3 v7's `arc()` API with method chaining to define the mouth's inner/outer radii and angle range. All elements are drawn declaratively, with the layers positioned via a grouped translation.