This example shows a simple interactive visualization: a red circle echoes the user’s mouse position within an SVG canvas. The circle responds in real time, maintaining its center exactly where the cursor moves over the 960×500 display. Built with React, the app uses the `useState` hook to store the cursor’s coordinates and a `useCallback` handler to update them on each mouse event. Mouse movement data comes from the `onMouseMove` event, which captures the `clientX` and `clientY` properties.