This example shows a smiley face built with D3.js, featuring expressive eyebrows that animate up and down over a two-second cycle. The face is constructed by manipulating SVG elements, including circles for the eyes and a path for the mouth, all grouped and positioned via translation transforms. The animation is driven by a chained sequence of `transition().duration()` calls, which move the eyebrows group along the y-axis. The code imports `select` and `arc` from D3, using the latter to generate the mouth’s arc path geometry.