A yellow circle follows the mouse cursor across a blank SVG canvas. The visualization demonstrates React mouse event handling, with the circle's position updating in real time based on the user's pointer movement. The code uses React's `useState` and `useCallback` hooks within a functional component, rendering an SVG `<circle>` element whose `cx` and `cy` attributes are set from the `clientX` and `clientY` coordinates captured by the `onMouseMove` event. The viewport is fixed at 960 by 500 pixels.