This example demonstrates fundamental DOM manipulation with D3.js by rendering a smiley face whose eyebrows move. It first uses `d3.select` to target the SVG element, sets its dimensions based on the viewport, and appends a rounded rectangle as the canvas background. The code relies on basic SVG attributes like `width`, `height`, and `rx`, while the interactive eyebrow animation is driven by D3’s data-binding and update patterns, though the specific motion logic is not shown. The visualization highlights how D3 can directly control SVG structure from JavaScript.