A smiley face drawn with D3.js animates its eyebrows up and down in a looping transition. The SVG face uses a yellow circle, two eye circles, and an arc-generated mouth, while the eyebrows are rectangles that move via chained `transition.attr` calls over two-second intervals. D3 v5’s `select` and `arc` APIs build the static elements, with the animation driven by D3’s transition system.