A circle rendered as an SVG element follows the mouse cursor within a fixed 900×500 viewport. The React component `App` tracks pointer coordinates via an `onMouseMove` handler, updating the circle's `cx` and `cy` attributes through state managed by `useState`. The initial position is centered at half the width and height. React 16.13.1 and ReactDOM render the interactive graphic, which updates smoothly as the user moves the mouse over the SVG area.