This example shows a yellow smiley face built with D3.js that animates its eyebrows in a continuous up-and-down motion. The face is rendered as SVG elements, including circles for the eyes and an arc-generated path for the mouth, all positioned within a central group. Using D3 selections and the `transition().duration()` method, the eyebrows—drawn as rectangles—move in a two-step sequence that repeats once. The code imports `select` and `arc` from the D3 v5 library to create the shapes.