A circle follows the mouse cursor across a full-screen SVG canvas. The visualization demonstrates real-time interaction, mapping the pointer’s client coordinates to the circle’s center position. Built with React and D3, it uses the `useState` hook to track mouse movement and the `onMouseMove` event on the SVG element to update the circle’s `cx` and `cy` attributes dynamically. The rendering relies on ReactDOM to draw the SVG circle, with the D3 `range` import unused in this minimal example.