A single yellow circle with a black stroke follows the mouse cursor across a full-screen SVG canvas. The circle’s position updates to the exact coordinates of the pointer via React’s `useState` and `useCallback` hooks, which capture `clientX` and `clientY` from the `onMouseMove` event. The application uses ReactDOM to render the SVG element, with the viewport dimensions derived from `window.innerWidth` and `window.innerHeight`. The example demonstrates basic pointer tracking with a minimal, event-driven React component.