A full-window SVG follows the mouse, drawing a single circle that tracks the cursor's movement in real time. The React application uses the `useState` and `useCallback` hooks to store and update the mouse coordinates based on `onMouseMove` events, then renders the circle with its `cx` and `cy` attributes tied to that state. Rendered via ReactDOM into an SVG canvas, the visualization demonstrates a minimal, direct interaction between user input and graphical output.