This example shows a simple interactive visualization where a single circle follows the user's mouse movements across an SVG canvas. The React component tracks the mouse position using the `useState` and `useCallback` hooks, updating the circle's `cx` and `cy` attributes in real time. The code uses React 16.9.0 with `ReactDOM.render` to mount the SVG element, and the initial mouse position is set to the center of the 960×500 viewport.