A yellow circle follows the mouse cursor across an SVG canvas, updating its position in real time. Built with React and SVG, the app uses a `useState` hook to track mouse coordinates from an `onMouseMove` event handler on the `<svg>` element. The circle radius is fixed at 30 pixels, and the canvas dimensions are 960 by 500, with the initial cursor position centered. The example demonstrates interactive state management and event-driven rendering in a React-based visualization.