Smiley face part 1
This example shows a simple smiley face drawn with React and D3’s `arc` generator for the mouth. A yellow circle with a black stroke forms the head, while two solid black circles serve as eyes. The mouth is a full circular arc with inner and outer radii, rendered as an SVG path. The SVG canvas is fixed at 960 by 500 pixels, with all elements positioned relative to the center using a `translate` transform. React renders the component hierarchy, and D3’s `arc` API computes the path data.