This example builds a smiling face using D3 v5, rendered as an animated SVG. It constructs the head, eyes, eyebrows, and mouth from primitive shapes, with the eyebrows performing a looping vertical bounce via chained `transition` calls. The code uses D3’s `select` and `arc` APIs directly, setting shape attributes like `r`, `cx`, and `cy` to position elements relative to the SVG’s center. The face’s layout is defined by constants for eye spacing and offsets, demonstrating a simple, reusable composition pattern.