A smiling face is drawn from SVG primitives: a yellow circle for the head, two black circles for the eyes, two rectangles for eyebrows, and an arc path for the mouth. The example demonstrates animated transitions, with the eyebrows moving up and then back down over two seconds using chained `.transition().duration()` calls. The scene is centered within a 960×500 SVG canvas using a `g` element translated to the midpoint. The code imports `select` and `arc` from D3 v5, and constructs the mouth’s arc path with the `arc()` generator, specifying inner and outer radii and angular spans.