This example animates a simple cartoon face built entirely from SVG shapes. A green circle serves as the head, with two black circles for eyes, a dark arc for the mouth, and two rectangles for eyebrows. The eyebrows move up and down repeatedly in a looping animation using chained `transition().duration()` calls. The visualization is constructed with D3 v7, using `select` to target the SVG, `arc()` to generate the mouth path, and SVG primitives like `circle` and `rect`.