A yellow smiley face rendered as an SVG reacts to a repeating transition, with both eyebrows moving up and down in sync. The example demonstrates fundamental D3.js DOM manipulation by selecting an SVG element, appending groups, and drawing shapes like circles, rectangles, and an arc for the mouth. It uses `d3.select` and `d3.arc`, with `transition().duration()` to animate the eyebrow positions over 600-millisecond intervals. The face is centered using SVG transform attributes, and the code runs with d3.v5.