This example shows an interactive SVG face that follows the mouse horizontally across a 960×500 canvas. A single circle, positioned at the center vertically, reacts to mouse movement by updating its x-coordinate in real time. Built with React’s `useState` hook and the D3 `arc` library, the app renders a minimal smiley-face precursor. The SVG’s `onMouseMove` handler triggers state updates, demonstrating a simple pattern for combining React’s declarative rendering with D3’s geometry utilities.