A yellow circle follows the mouse cursor across an SVG canvas. The interface demonstrates basic pointer tracking using React state management, where `useState` stores the cursor’s `clientX` and `clientY` coordinates on each `mousemove` event. The `circle` element’s `cx` and `cy` attributes update dynamically from this state, while `circleRadius` remains fixed at 30 pixels. Rendered entirely with SVG within a React component, the example shows how declarative data binding enables smooth, responsive interactions without additional D3 utilities.