This visualization combines a bar chart of daily step counts with a line chart of calories burned over a 160-day fitness activity period. The bars, rendered as SVG rectangles with alternating purple shades, show steps on the left y-axis, while the green line with labeled points tracks calories on the right y-axis. The code uses D3 v7 with `scaleBand` for the x-axis, `scaleLinear` for both y-axes, and a `d3.line` generator to connect data points sampled every tenth day from the CSV dataset.