A smiling face built from basic SVG shapes in D3 v5 demonstrates modular JavaScript composition. The code constructs circles, rectangles, and an arc-generated mouth using `d3.arc`, then positions them relative to a central group. Eyebrows animate downward and back via chained `transition().duration()` calls, simulating a blink-like motion. The face uses fixed dimensions from the SVG viewport, with all elements drawn programmatically from math constants rather than external data.