This example visualizes population counts by age group over time as a single red line chart. The data is loaded from a CSV file hosted on GitHub Gist and rendered as an SVG. Using D3 v5, it employs `scaleTime` for the x-axis, `scaleLinear` for the y-axis, and a `line` generator to draw the path. Axis labels and a chart title are styled via CSS, with gridlines created through axis tick settings.