A smiley face rendered as an SVG follows the mouse cursor across a 960×500 canvas. The example combines React for state management with D3.js for SVG generation, using a `circle` element whose `cx` and `cy` coordinates update via a `mouseMove` event handler. The React `useState` hook tracks the cursor position, and `useCallback` optimizes the event handler. Though the code defines a yellow face with black outline and two eye circles in an HTML comment, the interactive version displays only a single moving circle, driven by `ReactDOM.render` and D3 v5.