A circle follows the mouse cursor across a 960x500 SVG canvas in real time. Built with React 16.9, the app uses the `useState` and `useCallback` hooks to track pointer coordinates from the SVG element’s `onMouseMove` event, updating the circle’s `cx` and `cy` attributes via React’s declarative rendering. The initial mouse position is centered, and the component re-renders on every move without external data or animation libraries.