Let's make a face with D3.js!
A smiling face built from SVG primitives demonstrates basic D3.js DOM manipulation. Circles form the head, eyes, and mouth, while rectangles serve as eyebrows. The eyebrows animate via chained `transition().duration(2000)` calls, moving down and up over four seconds. The mouth is drawn using the D3 `arc` shape generator, and the entire composition is placed inside a red-background SVG canvas.