A simple green SVG face with a yellow circular head, black eyes, and a smiling mouth demonstrates basic D3 selection and styling. The code selects the SVG element with `d3.select` and applies a green background via `style`. It uses D3 v5 loaded from a CDN, with the SVG rendered in the browser and a hidden body overflow. The example highlights how D3 can manipulate SVG attributes and styles to create a static, playful visual without data binding or interactive features.