This example visualizes daily fitness activity trends over 150 days, comparing steps walked, calories burned, and active minutes as multi-line charts within a single SVG. Using React 19 and D3 v7, it parses CSV data with `d3.csv`, scales values with `d3.scaleLinear`, generates paths with `d3.line`, and renders `d3.axisBottom` and `d3.axisLeft` axes. The visualization includes a title, legend, and styled background, with active minutes scaled 100x for visibility.