This example shows a modular React smiley face built from reusable SVG components: a yellow background circle, two eyes, and a d3-shaped mouth arc. The `FaceContainer` groups all elements with an SVG `<g>` transform, centering the face via `centerX` and `centerY` props. Each component receives numeric props for sizing and positioning, while the mouth uses `d3.arc` to generate a curved path between specified angles. The face is rendered with React DOM into an SVG canvas, with D3 v7 providing the arc generator.