A smiley face rendered as a yellow circle with eyes and a mouth, built using React and D3. The code creates an SVG with a central group transformed to the center of the 960×500 viewport, drawing the face with circles and a D3 arc for the mouth. It uses ReactDOM to render the component and D3’s `arc` API to define the mouth’s inner and outer radii and angular range, illustrating how React manages SVG elements while D3 handles geometric path calculations.