This example builds a smiling face from basic SVG shapes using D3.js, with animated eyebrows that move up and down in a looping transition. The code selects an SVG element, centers a group, and appends a circle for the head, circles for eyes, rects for eyebrows, and a path for the mouth generated with the `d3.arc()` helper. Using `d3.transition()` and `.duration(2000)`, the eyebrows shift vertically twice, creating a repetitive motion. The demonstration focuses on fundamental DOM manipulation—such as `.append()`, `.attr()`, and chained transitions—while rendering entirely in SVG with no external data.