This example demonstrates fundamental DOM manipulation with D3.js by constructing a smiley face whose eyebrows animate. It shows how D3’s selection and mutation methods create and update SVG shapes directly. The code uses `d3.select`, `d3.arc`, and attribute getters to size elements from the SVG element, rendering the face entirely with vector graphics. The face’s eyebrows move, but the specific motion pattern is not detailed in the provided source. The implementation relies on D3 v5 and operates on a blank SVG canvas with no external data source.