Let's make a face with D3.js!
A yellow smiley face with black circular eyes, rectangular eyebrows, and an arc-based mouth is rendered entirely in SVG. The example demonstrates fundamental DOM manipulation and animation with D3 v5, using `d3.select`, `d3.append`, and `d3.arc` to generate the facial features. Eyebrows animate via chained `transition` calls that move their group vertically over two seconds, then return. The face is centered using an SVG `<g>` element with a computed translation, and all geometric values are defined as named constants for clarity.