Smily Face Part I
This example builds the upper half of a smiley face using React components and D3.js. It shows a yellow background circle, two black eyes, and a partial mouth arc, all rendered as SVG elements within a coordinate system centered on the canvas. The mouth shape is generated with D3’s `arc()` generator, which produces a path based on inner and outer radii and angular start and end points. The face’s geometry is parameterized through component props, allowing for flexible control over eye offset, radii, and stroke width.