This example draws a yellow smiley face using React for component structure and D3’s `arc` generator to create a mouth shape. The face consists of a circle background, two eyes, and a filled arc representing a smile, all rendered as SVG elements. The code uses ReactDOM to mount the app and computes geometry from fixed dimensions, with stroke widths and offsets defined as constants. The D3 `arc()` API generates the mouth path with inner and outer radii and angular start and end positions.