This animated heat-histogram shows how summer temperature distributions have shifted over time, cycling through the years 1951, 1983, 1994, and 2005. A single SVG path, drawn with `d3.area` and `d3.curveBasis`, is used as a mask over five colored rectangles to create a multi-color histogram. Each year’s distribution is loaded from a TSV file, and `d3.interval` triggers transitions that update the path’s `d` attribute and animate the displayed year text.