A smiling face built with SVG renders a yellow circle, two eyes, and an arc-based mouth. D3.js v5 transitions animate the eyebrows, moving a group containing two rectangles upward and back down over a four-second loop. The code uses `d3.select`, `d3.arc`, and chained `transition().duration()` calls to manipulate DOM elements directly, with static attributes for spacing and dimensions defined in JavaScript.