This D3.js example demonstrates fundamental DOM manipulation by building an animated smiley face out of SVG shapes. The face, rendered with yellow circles for the head and eyes, and a path for the mouth, is constructed using `d3.select` and `svg.append`. The animation uses chained `transition().duration(2000)` calls to move the rectangular eyebrows up and down. The code uses D3 v5 and associates the SVG with a teal background via `.style`.