A smiling face follows the cursor across a full-screen SVG canvas. Built with React, the app tracks mouse movement via an `onMouseMove` event handler and updates component state with `useState`, re-rendering a single yellow circle to track the pointer. The visualization demonstrates React’s declarative approach to DOM updates, using `ReactDOM.render` to mount the component and SVG elements for rendering. No external data source is used; interaction is driven entirely by user input.