Let's make a face with D3.js!
A yellow smiley face with animated eyebrows demonstrates core D3.js DOM manipulation. The SVG face uses `d3.select` to append circles for the eyes and face, and an `arc` generator to draw the mouth. Eyebrows are rectangles that move up and down via chained `transition().duration()` calls, shifting the eyebrow group's transform. The code imports `select` and `arc` from the d3 module, builds the face from nested SVG groups, and runs in a 960×500 viewport.