A React component renders an SVG circle that follows the mouse cursor across a 960×600 viewport. The application tracks pointer coordinates through the `onMouseMove` event handler and stores them in state using the `useState` hook. The circle's `cx` and `cy` attributes update reactively as the `mousePostion` state changes, demonstrating a direct integration of React's declarative rendering with SVG. D3.js v6 is loaded but not actively used in this example, which instead relies purely on React 17 and ReactDOM for all interactivity and rendering.