A smiling face built from basic SVG shapes animates its eyebrows up and down in a continuous loop. The example demonstrates fundamental DOM manipulation with D3.js v5, using `select` and `append` to create circles, rectangles, and an arc path for the mouth. Two chained `transition().duration()` calls move the eyebrow group between two vertical positions. The face is centered within an SVG canvas using an affine transform, with all geometry defined by explicit numeric constants.