Fork of Smiley Face Part II
A React application renders a single yellow circle that follows the mouse cursor across the full browser window. The circle updates its position through React state managed by `useState` and `useCallback` hooks, responding to `onMouseMove` events on an SVG element. The visualization demonstrates interactive SVG rendering with React, using `ReactDOM.render` to mount the component and window dimensions to size the drawing area. The code includes commented-out example markup for a static smiley face, but the active implementation shows only the cursor-tracking circle.