A React application demonstrates mouse event handling by rendering a single SVG circle that follows the cursor across the viewport. The circle's position updates in real time through the `onMouseMove` event, which captures `clientX` and `clientY` coordinates and stores them in state via the `useState` hook. The `useCallback` hook optimizes the event handler. The visualization uses React 16.9 and renders directly to SVG, with the window dimensions determining the drawing area.