This scatterplot displays GDP variation over time for the USA and Germany, with a categorical color scale assigning each country a distinct color. An interactive legend allows users to click a country name to highlight its data points while fading the other nation's points, filtering the visualization. The chart is rendered with D3 v5 and SVG, using the `d3.scaleLinear` and `d3.scaleOrdinal` APIs for axes and color, while the legend and scatterplot are built from custom modular functions. Data is loaded from a CSV file via `d3.csv`.