This example renders a full-screen smiley face using React and D3 v7. It draws a yellow circle with a black stroke as the head, two eyes as offset circles, and an arc-based mouth created with the `d3.arc()` API. The visualization sizes dynamically to the browser window, using `window.innerWidth` and `window.innerHeight` to position elements at the center. All shapes are output as SVG elements within a React component, with the mouth path generated by the `arc` generator’s corner radius and angle settings.