HTML Starter
This example draws a cheerful smiley face as an SVG, with yellow circular head, black eyes, and a curved mouth arc. It demonstrates D3.js v5 selection and shape generation using `d3.select`, `d3.arc`, and attribute binding. The right eyebrow animates via chained `transition().duration()` calls, moving downward and back over two seconds. The 960×500 SVG canvas is centered with a `g` group transform.