A full-screen SVG circle, initially centered, does not respond to mouse movement; the program stores pointer position but never updates the circle's coordinates. Rendered with React 16.9 and ReactDOM, the app derives viewport dimensions from `window.innerWidth` and `window.innerHeight`, then draws a single fixed-radius circle via JSX in an SVG element. No event listeners, state updates, or motion logic appear in the code, so the circle remains static despite the title's implication of following behavior.