A single gray circle follows the mouse cursor across an SVG canvas. The example demonstrates React state management with the `useState` and `useCallback` hooks, updating the circle’s `cx` and `cy` attributes on every `mousemove` event. React renders the SVG element directly, with the circle’s position derived from the client coordinates of the pointer. The visualization uses React 16.9 and ReactDOM, keeping the interaction simple and responsive without additional data sources or animation libraries.