Fork of Smiley Face Part III
This example shows a yellow smiley face rendered as SVG, with two eyes, a curved mouth, and a thick black outline. It builds the face from reusable React components, including `BackgroundCircle`, `Eye`, and `Mouth`, and positions them within a centered `<g>` element. The mouth uses D3’s `arc` generator to create a semicircular path, while the eyes and background are plain SVG circles. The project runs on React 16 and D3 v5, with coordinates and sizes defined as constant variables in the main React component.