A mouse follower demonstrates real-time pointer tracking within an SVG canvas using React state. As the user moves the mouse over the 800×800 viewport, a circle smoothly repositions itself to match the cursor’s x and y coordinates. The component uses React’s `useState` hook to store the mouse position and `useCallback` to handle the `onMouseMove` event efficiently. While the code includes D3 v7 as a dependency, the interaction itself relies purely on React’s event handling system, not on D3-specific visualization APIs.