A 960-by-500 SVG circle follows the mouse cursor across the canvas, its center updating in real time to match the pointer’s client coordinates. Built with React and ReactDOM, the example uses the `useState` hook to store the cursor position and a `useCallback`-wrapped `onMouseMove` event handler to update it. The SVG circle is rendered with a fixed radius of 30 pixels, demonstrating state-driven drawing within a minimal React component.