This example shows a single unfilled circle that follows the mouse cursor across the full browser window, rendered as an SVG element. The circle’s center coordinates update continuously on mouse movement, using React’s `useState` and `useCallback` hooks to manage and optimize state changes. The visualization is built with React 16.9 and ReactDOM, rendering directly to the DOM, with the SVG’s `onMouseMove` event driving the interactive behavior. The underlying code includes commented-out static smiley-face circles, indicating the fork’s evolution from a fixed illustration to a mouse-tracking interactive graphic.