This example demonstrates a real-time interactive visualization where a circular SVG element follows the mouse cursor across a 960x500 canvas. Built with React 17 and D3 v7, the application uses React’s `useState` and `useCallback` hooks to track mouse coordinates through an `onMouseMove` event handler on the `<svg>` element. As the pointer moves, React re-renders the circle’s `cx` and `cy` attributes, updating its position instantly. The visualization highlights how React manages state-driven updates for DOM elements, contrasting with D3’s imperative approach to data binding.