Let's make a face with D3.js!
A smiling face composed of SVG shapes animates on a yellow circular head, with eyebrows that raise and lower repeatedly. The example demonstrates D3.js v5 selections and transitions, using `append`, `attr`, and chained `transition().duration()` calls to animate rectangles. It builds the face with primitive shapes: a circle for the head, ellipses for eyes, a path generated by the `d3.arc` function for the mouth, and animated rects for eyebrows.