A smiling face rendered in SVG follows the mouse across the screen. Built with React and D3 v5, the example uses D3’s `arc` generator to create the mouth, while the face circles, eyes, and stroke are defined as React components. The entire SVG group is translated to the viewport center, and the mouse follower behavior is implied by the full-screen, overflow-hidden layout, though no explicit mouse event handlers appear in the code. The static smiley face adapts to its container dimensions.