A yellow circle follows the mouse cursor across a full-screen SVG canvas, reacting to every pointer movement in real time. The example demonstrates React state management and event handling with a simple interactive visualization. Using the `useState` and `useCallback` hooks, the application tracks the mouse's `clientX` and `clientY` coordinates and updates the circle's `cx` and `cy` attributes accordingly. Built with React 16.9 and rendered as SVG nodes through `ReactDOM.render`, the visualization responds directly to pointer events without additional data sources or processing libraries.