Fork of Let's make a face with D3.js!
A yellow smiley face drawn with SVG shows off basic D3.js DOM manipulation: the code appends circles for eyes and a mouth, uses a path with `d3.arc` for the smile, and animates the eyebrows with repeated `transition.attr` calls that shift their vertical position over two seconds. The face is centered by translating a grouping element, with fixed numeric constants for eye spacing, radius, and eyebrow sizing. The animation loops once, lifting the eyebrows upward then returning them, demonstrating chained transitions on the same selection.