A smiley face drawn in SVG animates as its eyebrows bounce up and down. Built with D3.js v5, the example constructs circles for the eyes and a path using the `arc` generator for the mouth, then applies chained `transition()` calls to shift the eyebrow group’s transform. The code demonstrates core DOM selection and manipulation via `d3.select`, plus attribute setting and SVG grouping, with no external data source.