This example uses D3.js (v5) to draw an animated smiley face in SVG. It shows a yellow circle with two eyes and a mouth, whose eyebrows move up and down via chained `transition()` calls. The code constructs the face using `select`, `append`, and `attr`, and generates the mouth path with the `arc` API. The animation runs on page load with a 2-second duration per eyebrow movement.