A demonstration of D3 version 6, this example draws a static smiley face as SVG circles and a path. Using `d3.select` and `append` to create elements, it animates the eyes with chained `transition().duration()` calls that alternately shrink and grow the circles' radii. The mouth is generated via `d3.arc()`, setting inner and outer radii with start and end angles, all rendered in an SVG canvas without external data.