A smiley face assembled from SVG shapes animates in D3.js v5: a yellow rectangle transitions to green, and two eyebrows rotate as the mouth flips upside down. The code demonstrates fundamental DOM manipulation with `d3.select`, appending grouped circles, rectangles, and an `d3.arc`-generated path into an SVG canvas. Transitions via `.transition().duration(2000)` smooth the color and transform changes over two seconds.