This line chart shows the relationship between age and daily steps, with age on the x-axis and daily step counts on the y-axis. The data is loaded from a GitHub gist via `d3.csv` and sorted by age to create a continuous steelblue line. The visualization uses `d3.scaleLinear` for both axes, a `d3.line` generator to produce the path, and `d3.axisBottom` and `d3.axisLeft` for the labeled axes, all rendered as SVG within a 600×400 pixel chart area.