This example builds a smiley face entirely with React and D3.js, rendering SVG components. It defines React components for the face’s background circle, eyes, and mouth, with the mouth drawn using the D3 `arc` function to create a precise arc path. The SVG canvas is 960 by 500 pixels, centered with a yellow circle, black stroke, and positioned eyes and mouth via transforms and offsets. The code uses ReactDOM to render the composed `App` component into the HTML root element.