A yellow circle follows the mouse cursor across a blank SVG canvas, updating its position in real time as the user moves the pointer. The visualization uses React state with the `useState` and `useCallback` hooks to track mouse coordinates, and ReactDOM renders the circle via SVG. D3 v6’s `arc` function is imported but unused; the core interaction relies on the SVG `onMouseMove` event handler. The fixed canvas is 960 by 500 pixels, with the circle’s radius set to 30.