A full-screen React application renders a single blue circle that tracks the mouse position within an SVG canvas. The component uses the `useState` and `useCallback` hooks to manage and update the circle’s center coordinates on every `mousemove` event. Rendering is performed with React DOM into a root div, while the SVG `circle` element receives its `cx` and `cy` attributes directly from the current state. The example demonstrates declarative state-driven graphics with minimal setup, using only React’s core APIs and no additional data sources.