This D3.js example builds a smiling cartoon face from scratch using SVG primitives. A yellow circle forms the head, while two circles with animated rectangular eyebrows and an arc-shaped mouth are positioned to create the expression. The right eyebrow repeatedly moves up and down via chained `transition().duration(2000)` calls, demonstrating D3's animation capabilities. All elements are scaled and centered using the `select` and `append` API from d3 v5.