A single dark circle follows the mouse cursor across an SVG viewport, creating a direct and immediate interactive connection between user input and visual output. Built with React hooks for state management and event handling, the circle’s position updates on every mousemove event, while D3’s `arc` generator defines a static mouth shape visible in the initial markup. The visualization renders exclusively through SVG elements, with React managing the circle’s coordinates and D3 providing geometry utilities. This minimal example demonstrates the seamless integration of React’s declarative rendering with D3’s computational functions for interactive graphics.