A circle follows the mouse cursor across an SVG canvas. The visualization updates the circle’s position in response to every mouse movement event. Built with React 16.9, it uses the `useState` hook to track the cursor’s `clientX` and `clientY` coordinates and the `useCallback` hook to handle the `onMouseMove` listener. The circle’s center is set via `cx` and `cy` attributes on the SVG `<circle>` element, with a fixed radius of 30 pixels.