This example displays a choropleth map of Portland neighborhoods, rendering geographic boundaries as green SVG paths. The map uses a conic equal-area projection configured with `d3.geoConicEqualArea` and `d3.geoPath` to project and draw the shapes. Data is loaded from a TopoJSON file via `d3.json` and converted to GeoJSON features using `topojson.feature`. The visualization is built with React, where the `Marks` component maps each feature to a path element, and styling is applied through CSS to highlight the neighborhood borders.