This example shows how a user’s pointer position directly controls the placement of a single circle within an SVG canvas. As the mouse moves over the full-width, full-height SVG, the circle centers itself exactly at the cursor’s client coordinates. Built with React (using the `useState` and `useCallback` hooks) and D3 v7 for rendering, the app updates the circle’s `cx` and `cy` attributes through React state changes triggered by the `onMouseMove` event. The visualization demonstrates a simple, responsive interaction pattern without external data sources.