This example demonstrates fundamental DOM manipulation with D3.js by rendering a smiley face whose eyebrows move. The face is drawn as SVG elements, and the eyebrows are animated using D3’s `transition.attrTween` to shift their vertical position. The code uses `d3.select` and `d3.append` to build the shapes, while `d3.interval` drives the continuous motion. The page loads D3 v5 from a CDN and applies styling from an external stylesheet, with all script logic contained in `bundle.js`.