This example shows a single circle that follows the mouse pointer across a full-window SVG canvas. The circle uses the current mouse coordinates as its center, with a fixed radius of 40 pixels. The application tracks pointer movement through React's `useState` hook and an `onMouseMove` event handler, updating the circle's `cx` and `cy` attributes in real time. The visualization is rendered with React and SVG, using ReactDOM to mount the component, and initializes the circle at the center of the window.