This stacked bar chart visualizes religious demographics across the top 20 most populous countries, with population values in millions. The visualization uses D3.js version 7.8.5, employing `scaleOrdinal` and `schemeCategory10` for color encoding, `flatRollup` and `stack` for data aggregation, and `scaleLinear`/`scaleBand` for axes. A color legend provides interactive filtering—hovering a religion name highlights the corresponding segments while fading others. The data comes from the CSV file `religionByCountryTop20.csv`, with responsive layout handled by `observeResize` from `@curran/responsive-axes`.