This example renders a simple smiley face using React and SVG primitives. It shows a yellow circle with black eyes and a curved mouth, composed from separate component files for the face, eyes, and mouth. The `Mouth` component leverages the `arc()` API from d3 to generate an SVG path, while the `Face` component assembles these parts within an SVG group. The entire graphic is defined declaratively through React component properties like `centerX`, `eyeOffsetX`, and `mouthRadius`.