Fork of Smiley Face Part II
This example renders a large, yellow smiley face that fills the browser window using React and D3.js. The face is composed of SVG circles for the head, eyes, and clipped irises, plus a mouth drawn with D3's `arc` generator. The code uses `d3.arc()` to create the mouth path and React's `ReactDOM.render` to draw the SVG elements, with dimensions based on `window.innerWidth` and `window.innerHeight`. The face is centered via an SVG transform, and the iris clipping paths use `clipPath` elements.