A yellow smiley face rendered as an SVG circle follows the mouse cursor across a full-screen viewport. Built with React, the component tracks pointer coordinates via the `onMouseMove` event and updates the circle's `cx` and `cy` attributes using the `useState` hook. The rendering relies on ReactDOM and SVG elements, with a production build of React 16.9.0. The visualization demonstrates a simple, reactive data binding between user input and graphical output, with no external data source.