A smiley face follows the mouse cursor across an SVG canvas, with its position updating in real time. The visualization uses React state and the `useState` and `useCallback` hooks to track mouse coordinates, which are passed to an SVG `<circle>` element’s `cx` and `cy` attributes. The `onMouseMove` event handler on the `<svg>` element triggers the state update, while ReactDOM renders the component. No D3 APIs are used; the example relies purely on React’s declarative rendering with SVG.