Fork of Smiley Face Part II
This example shows a yellow smiley face rendered as a full-screen SVG, with two circular eyes and an arc-based mouth centered on the viewport. It uses React components and the D3 `arc` generator to define the mouth’s inner and outer radii and angles. The SVG is dynamically sized using `window.innerWidth` and `window.innerHeight`, and the face is positioned via a `<g>` transform. The background circle is a separate React component, with stroke width and radius passed as props, while D3 v6 handles the path geometry.