This example shows a smiley face whose single eye follows the mouse cursor across the screen, with the circle’s position updating in real time. Built with React, it uses the `useState` and `useCallback` hooks to track mouse coordinates and re-render an SVG `<circle>` element. The SVG’s `onMouseMove` event handler triggers state updates, and ReactDOM renders the component into the root div. The visualization uses a fixed viewport matching the browser window and demonstrates interactive pointer tracking in a minimal, responsive setup.