Let's make a face with D3.js!
A smiling face is drawn with SVG shapes, and its eyebrows animate upward and downward in a loop. The face is constructed using D3.js v5’s `select` and `append` to create circles for eyes, rectangles for eyebrows, and a `path` for the mouth via the `arc` shape generator. The eyebrows’ movement is driven by chained `transition().duration()` calls that alter the group’s `transform` attribute. The code relies on D3’s DOM manipulation and transition APIs, with all rendering occurring in an SVG viewport.