This example visualizes population trends over time for multiple regions, displaying separate lines for each region from 1950 to 2100. The data is sourced from UN population estimates and is processed by reshaping wide-format CSV data into a tidy format using custom functions. The visualization uses D3 v5 with SVG rendering, employing `d3.line` with curve interpolation, `d3.scaleTime` and `d3.scaleLinear` for axes, and `d3.nest` to group data by region. A color legend is rendered using a custom function that utilizes `d3.scaleOrdinal` with `d3.schemeCategory10`.