This bar chart visualizes the population of each country in 2015, using a horizontal bar for each nation. Constructed with the Vega-Lite API, the chart serializes a declarative specification through `vl.markBar()` and `vl.x().fieldN('country')`/`vl.y().fieldQ('population')`. The code registers Vega, Vega-Lite, and the tooltip handler, then loads CSV data from a GitHub gist via `d3.csv`. The visualization renders to SVG and adapts to the browser window size.