A D3.js smiley face, built from SVG primitives, demonstrates fundamental DOM manipulation and transitions. A green circle forms the head, with two dark circles for eyes and an orange arc for the mouth, all positioned using geometric constants. The animation shows both rectangular eyebrows moving up and down together via chained `transition().duration()` calls that modify their container's `transform` attribute. The code uses D3 v5 selections and the `arc` generator to construct the mouth path, with all elements grouped and translated to the SVG center for easy positioning.