This example animates a simple face, including an elliptical head, eyes, pupils, eyebrows, and a mouth, with the eyebrows looping up and down in a continuous cycle. The loop is achieved by chaining two D3 transitions—one moving the eyebrow group down, the next moving it up—and invoking the same function again in the `transition.on("end")` callback. The SVG is rendered using D3 v5, with shapes drawn via `.append()` for ellipses, circles, polylines, and an arc, and all positioning handled through `transform` attributes.