A circle follows the mouse cursor across an SVG canvas, centering itself on the pointer’s coordinates. The example demonstrates React state management to track mouse movement, updating the circle’s position on every move event. It uses React’s `useState` and `useCallback` hooks alongside D3 v6 for the SVG rendering, with an initial circle centered at 480, 250. The visualization responds interactively in real time, showcasing a minimal integration of React and D3 for dynamic graphics.