This choropleth map visualizes global CO₂ emissions by country in million metric tons, using a red sequential color scale where darker shades represent higher emissions. Built with D3.js v7 and TopoJSON, it renders world countries as SVG paths via a Natural Earth projection and `d3.geoPath()`. Hovering over a country triggers a tooltip showing its name and emission value while temporarily highlighting the region. A gradient legend at the bottom uses `d3.scaleSequential` with `d3.interpolateReds` to communicate the mapping from data values to colors.