This example animates a smiling face drawn with D3.js, showing a looped sequence where the eyebrows rise and fall. It demonstrates core SVG manipulation by selecting the root `<svg>` element and appending groups and shapes, including circles for the face and eyes, rectangles for the eyebrows, and a path for the mouth, which is generated using the `d3.arc()` function. The animation is driven by a chain of `.transition().duration(2000)` calls that move the eyebrow group’s `transform` attribute between two vertical positions, using D3 v5’s built-in transition API. The face is centered via a `translate` transform, and the SVG canvas is a fixed 960×500 pixel space.