This example uses D3.js to construct a smiley face out of basic SVG shapes, then animates it. The code builds a blue circle for the head, eyes, and a mouth using `d3.arc`, while two rectangular eyebrows are moved up and down via chained `transition.attr` calls with a 2000ms duration. The animation runs in a loop, demonstrating select-and-append DOM manipulation and declarative transitions on SVG elements.