This example demonstrates a simple animated face built with D3 v4 and React, rendered as SVG on an HTML page. The purple background hosts a yellow circle with black stroke, two eyes, and an eyebrow that transitions vertically over two seconds before returning. A mouth is drawn using an arc path generator from D3. The code selects the SVG element, uses method chaining for attribute setting, and applies transitions with `transition().duration()` to animate the eyebrow.