This example demonstrates a smiley face that follows the mouse cursor across an SVG canvas. As the user moves their pointer, a yellow circle with a black outline tracks the cursor’s exact position in real time. The visualization is built using React’s `useState` and `useCallback` hooks to manage and update the mouse coordinates, with the `onMouseMove` event handler updating the state. D3’s `arc` function is imported but unused, while ReactDOM renders the SVG circle whose `cx` and `cy` attributes are bound to the tracked position, creating a responsive interactive effect.