So rather than focusing on a stationary settlement, where you're building things that don't move, you'd have the same focus on satisfying your people's needs, but with a group of nomads, so you'd have to have houses that could be packed up to move, and where you're playing would change with the seasons as you're moving your herds to where they can eat or following after game to hunt, that sort of thing. Obviously the term "city-builder" wouldn't really apply but I feel it'd be the closest genre even with the change to a moving settlement. I know there's Airborne Kingdom, and some other similar games, but my understanding is that you're basically still building a regular city, just on a moving platform. You're not really following resources or taking care of a moving population.