A smiley face drawn with D3.js animates its eyebrows in a looping vertical motion. The SVG face uses simple shapes: a yellow circle for the head, two circles for the eyes, rectangles for the eyebrows, and a D3 arc for the mouth. The animation is driven by chained `transition().duration()` calls on the eyebrow group, moving it up and down. The code demonstrates fundamental DOM manipulation via `select` and `append`, with hardcoded dimensions for the 960×500 viewport.