A smiling face built from SVG shapes animates its eyebrows up and down in a looping transition. The example constructs the face from basic geometric elements—a yellow circle for the head, two small circles for eyes, rectangles for brows, and an arc path for the mouth—centered via a translated group. Using D3 v5, the code applies chained `transition()` and `.attr()` calls to move the eyebrow group repeatedly, while the `d3.arc()` helper generates the mouth’s curved outline. The rendering relies on SVG appended directly to the page’s `<svg>` element.