A smiling face, drawn as a single SVG circle, follows the mouse cursor across a 960 by 500 canvas. The React application tracks pointer movement via the `onMouseMove` event, updating the circle's center coordinates in its state. The reusable `useCallback` hook optimizes the event handler, and ReactDOM renders the interactive graphic inside the `#root` div. The example demonstrates real-time state-driven SVG redrawing using React 16.9.