This example animates a simple smiling face built entirely with D3 shapes. The face consists of a yellow circle, two black eyes, and a curved mouth created using the `d3.arc` path generator. Eyebrows animate with two sequential `transition().duration()` calls, first moving upward and then rotating via `attr('transform', rotate())`, while the face is centered using SVG group transformations. The code uses D3 v5 selections and transitions on SVG elements, with all coordinates computed from the SVG’s height and width attributes.