This fork of Observable’s pie chart example embeds an interactive D3.js (v5) visualization via an iframe into a minimal HTML page. The chart renders the U.S. population by age group, using `d3.pie()` and `d3.arc()` to draw wedges, with a spectral color scale and labels positioned by `d3.arc().centroid`. Data comes from a local CSV file. The styling is handled with CSS, and the code leverages Observable’s `PieChart` function.