A circle follows the mouse cursor across an SVG canvas. The visualization uses React's `useState` and `useCallback` hooks to track mouse coordinates, updating the circle's `cx` and `cy` attributes on every `mousemove` event. The SVG is rendered with React, while D3 v6 is loaded but not directly used for this interaction. The circle has a fixed radius of 20 pixels, and the canvas is 960 by 500 pixels.