This example shows a smiley face built from SVG shapes, with eyebrows that animate in response to the viewer’s actions. The code demonstrates fundamental DOM manipulation with D3.js v5, using `d3.select` and `d3.append` to create the face’s elements. It relies on the `d3.arc` generator for the mouth and applies simple transitions to move the eyebrows. The page reads the client’s viewport dimensions to size the SVG canvas, and styling is handled via an external stylesheet.