This example shows a yellow smiley face built with SVG elements in D3.js, whose eyebrows animate upward and downward in a looping transition. The code constructs the face using simple shapes: `circle` for the head and eyes, `rect` for the eyebrows, and a `path` generated with the `d3.arc` function for the mouth. D3 selections and the `transition().duration()` method drive the eyebrow movement, while the SVG is centered within a fixed 960×500 viewport using a translated `<g>` container.