This example builds a smiling face out of basic SVG shapes, then animates its eyebrows with a looping transition. D3 v7 selects the SVG and uses the `arc` generator to draw the mouth as a half-ring path, while circles and rectangles form the eyes and brows. The animation runs for two seconds per eyebrow movement, creating a repeated up-and-down motion. The code demonstrates D3 selections, transitions, and the `arc` API, all rendered directly to SVG.