A smiley face built with D3.js animates by raising and lowering its eyebrows. The code selects an SVG canvas and constructs the face from basic shapes, including circles for eyes and a path for the mouth using `d3.arc`. Eyebrow movement is achieved with chained `transition().duration()` calls that shift the rectangle positions over two seconds. The example uses D3 v5, imported via `d3.select` and `d3.arc`.