This example demonstrates how to build an animated smiley face using D3.js, showing a yellow circle with eyes, eyebrows, and a mouth. The eyebrows first move upward over two seconds and then return to their original position, creating a simple raised-eyebrow animation. The code uses D3’s `select` and `append` methods to construct SVG elements, while the mouth is drawn with the `arc` shape generator. The eyebrow motion is driven by chained `transition` calls that animate the `transform` attribute.