This visualization displays global population trends over time using multiple lines, one for each region, with a vertical black bar indicating the currently selected year. The chart is rendered with SVG using D3 v5, with an interactive mouse listener on a transparent rectangle that updates the selected year. Population data comes from UN estimates and projections loaded via CSV, and the line chart uses D3's `line` and `curveBasis` for smooth paths, while color encoding is handled by `scaleOrdinal` with `schemeCategory10`. Axes, ticks, and labels are generated using `axisBottom`, `axisLeft`, and `scaleTime`/`scaleLinear`.