A parameterized smiley face built with React and D3 v7 renders as layered SVG circles and an arc-based mouth. The `Face` component composes `BackgroundCircle`, `Eyes`, and `Mouth`, each accepting numeric props for position, size, and stroke width. The mouth uses D3's `arc` generator to draw a partial annulus between inner and outer radii, with angles set to a half-turn. The React app instantiates a single 960×500 face centered at the midpoint, with fixed eye offset and radius values.