This scatterplot visualizes GDP variation over time for multiple countries, with each dot colored by country and opacity highlighting a selected country while dimming others. Users click legend items to filter the visualization. The chart uses D3 v5 with SVG rendering, `scaleLinear` for axes, `scaleOrdinal` with `schemeSet2` for colors, and custom `scatterplot` and `colorLegend` modules. Data loads from a CSV file containing yearly GDP percentages.