To start work on the new tribal migration mechanics, I decided to revisit one of the integral parts of the group migration, which is polity prominence transfer. Polity prominences are an abstraction which allow the simulation to track how much presence a particular polity (ie. a tribe) has within a particular human group. Those prominences change over time and can be partially transferred from one cell to neighboring cells, which is what allows polities to expand their territory. 

There are right now two main ways prominences can move between cells, by group migration, and by polity influence expansion. The first method is straightforward. When population migrates from one cell group to another, it carries with it a portion of every polity prominence present in the source group These prominences then merge with the ones already present (if any) in the target group. The second method involves a special kind of event that allows a particular polity to "influence", in a completely nondescript way, a neighboring cell group and establish or increase its prominence on that group.

My goal for this feature is to "rewrite" those two ways in which prominence is transferred since, right now, the process is almost fully dictated by the group from where the transfer initiates. And I want to give polities more agency on how their territories expand. The first step, which I already took, was to revisit the prominence update process, which was a very old and convoluted piece of code that tried to handle multiple things at the same time. Worst than that, it was full of patches that I had introduced over several versions, as I needed to handle special cases for events like tribe splitting and merging. Those patches did the work, but did it badly. So I ended up rewriting a big part of all that, made the code simpler and solved a bunch of math incongruences along the way. It actually took me less time than I expected, which felt like quite an accomplishment given how horrid was the original code. 

The next step will be to reimplement the two polity prominence transfer events. First, I'm going to split the group migration event into two events, one specific for unorganized bands, which will behave pretty much in the same way as they do in the current version, and one for groups under the influence of polities. The new event will evaluate what are the migration "goals" of the entire polity or tribe, which will allow for the polity to occupy specific regions and take over territories in a more sensical manner. Lastly, the "hand-wavy" polity influence expansion event will go away completely since its job is going to be taken over by the (hopefully) more realistic polity group migration event.

That's that for this update, until next week!