XCOM 2’ s procedural maps are built from ‘parcels’ – chunks of scenery that can be plugged together. A parcel might be a building or a parking lot, but Firaxis groups them into two kinds: open parcels are outdoors and easy to traverse, while closed variants have interiors and take longer to get around. The team has identified a golden ratio of open to closed, and an ideal map size, but there’s plenty of variety within those rules. “So we have these parcel sets, and they don’t intermix,” Solomon says. “We may say, ‘This is going to take place in the city centre,’ and so we have hundreds of parcels, built out of thousands of assets, just for city centres. And then we have, ‘Oh, now you’re going to a small town,’ and so we have a different set for those.” On top of these are layered variations for snow, desert or temperate zones, ensuring that even if you encounter the same parcel a few times, it’s rarely an identical repeat.