A React component renders an SVG circle that follows the mouse cursor across a 960×500 viewport. The app uses React hooks `useState` and `useCallback` to track pointer coordinates from `onMouseMove` events, updating the circle’s `cx` and `cy` attributes. The example demonstrates integrating D3’s `arc` import while relying on React’s declarative rendering for state-driven SVG updates, with a static yellow circle illustrating callback-driven interactivity.