Let's make a face with D3.js!
This example uses D3.js to build a smiling face out of SVG primitives, including a yellow circle, two eyes, and a mouth shaped with the `d3.arc` path generator. The face is centered within an SVG canvas via a `g` element transform, and the eyes and eyebrows are positioned using attribute math. A two-second `transition` animates the eyebrow group's `y` attribute in a loop, causing the eyebrows to move up and down. The code demonstrates fundamental DOM manipulation through D3's selection and chaining methods.