Three linked line charts track daily hospital occupancy in Denmark, Norway, and Sweden from 2020 to 2022, with a fourth combined chart overlaying all three countries for comparison. Each country’s trend is drawn with a distinct color, and hovering reveals a tooltip with the exact date and value. The visualization loads CSV data via `d3.csv`, parses dates and numeric values, and renders SVG line charts using D3’s scales, axes, and `d3.line` generator, with an animated transition for the combined view.