A smiley face built with D3.js animates its eyebrows in a looping upward-and-downward motion. The face is composed of SVG shapes: a yellow circle for the head, two circles for eyes, rectangles for eyebrows, and an arc-generated path for the mouth. The code uses D3 selections and the `arc` generator from `d3-shape`, along with chained `transition` calls to move the eyebrow group over repeated two-second intervals.