A D3.js animation demonstrates fundamental DOM manipulation by drawing a smiling face whose eyebrows move. The code uses D3 selections to append SVG shapes—a yellow circle, two eye circles, and rectangular eyebrows—onto a 960×500 viewport. Eyebrows animate by chaining `transition().duration(2000)` calls that translate their group element upward and back. A mouth is rendered as an arc path using the `arc()` generator. The example is a fork of a tutorial, built with D3 v5 and SVG rendering.