This interactive React and D3.js example displays a smiley face composed of SVG circles, including a large yellow face, two eyes, and a mouth arc. A separate circle tracks the mouse position across the canvas, its radius dynamically recalculated based on the cursor’s distance from the center. The code uses `useState` for mouse tracking and `d3.arc` to render the mouth. The face’s eyes and main circle are defined as reusable React components, with the overall layout fixed at 1000 by 500 pixels.