This stacked bar chart illustrates the estimated religious composition of the 20 most populous countries in 2010, with each bar segment colored by religious affiliation and scaled by population in millions. Users can hover over the color legend to highlight a specific religion across all countries, applying a fade effect to unrelated segments and raising the hovered stack to the front. Built with D3.js, it uses `flatRollup`, `stack`, `scaleBand`, and `scaleLinear` to structure and position the data, sourced from the Pew Research Center’s Global Religious Landscape report.