This example demonstrates fundamental DOM manipulation with D3.js by building a smiling face whose eyebrows move up and down. It uses D3’s `select` and `append` to create SVG circles, rectangles, and a path for the mouth, with the mouth drawn via the `arc` generator. The animation relies on chained `transition` and `duration` calls to shift the eyebrow group’s transform attribute. The code imports named methods from the d3 module and sets attributes like `r`, `cx`, and `d` directly on SVG elements.