This example demonstrates fundamental DOM manipulation with D3.js by building a smiley face from SVG primitives—a yellow circle, two eyes, animated eyebrows, and an arc-shaped mouth. The eyebrows transition upward and downward over two two-second intervals using D3’s `transition()` and `attr()` methods. The code imports `select` and `arc` from D3, sets explicit constants for eye spacing and eyebrow dimensions, and renders everything on an SVG canvas with a centered group transform.