A smiley face built with SVG and animated with D3.js demonstrates fundamental DOM manipulation. Yellow circular head, two eyes, rectangular eyebrows, and a curved mouth are created using D3 selections and the `d3.arc` path generator. The eyebrows repeatedly move up and down via chained `transition` calls, each lasting two seconds. The code uses D3 v5, imports `select` and `arc` from the library, and renders entirely in SVG without external data.