Fork of Let's make a face with D3.js!
This example builds a smiley face out of SVG shapes—a yellow circle, two eyes, and a mouth drawn with `d3.arc()`—and animates its rectangular eyebrows by chaining two `transition().duration()` calls. The code selects the SVG element with `d3.select`, appends a group for centering, and transitions the eyebrow container between two vertical offsets, creating a bobbing motion. It demonstrates fundamental DOM manipulation and chained transitions using D3 v5 without external data.