A single SVG circle follows the mouse cursor across a 960-by-500 canvas. The visualization uses React's `useState` and `useCallback` hooks to track pointer coordinates from the `onMouseMove` event, updating the circle's center position in real time. The code imports `range` from d3 but does not use it. The graph is rendered through React's `ReactDOM.render` method, with the SVG container set to hide page overflow.