This line chart visualizes projected global population by region from 1950 to 2100, using UN population estimates and medium-variant projections. A vertical black line marks a selected year, and moving the mouse across the chart updates the selection, re-rendering the visualization. The code uses d3.scaleTime, d3.scaleLinear, d3.line with curveBasis, and d3.nest for grouping, with SVG rendering and a color legend. Data is loaded via d3.csv from two datasets and processed through a custom melt function.