This example visualizes population over time by region using multiple lines, with a legend and axis labels. It uses d3.scaleTime, d3.scaleLinear, d3.scaleOrdinal, d3.axisBottom, d3.axisLeft, d3.line, d3.curveBasis, d3.nest, and d3.schemeCategory10. The data is sourced from UN population estimates and medium variant projections, melted from wide to long format. The visualization renders as an SVG with a title and color legend.