Does any one know what the exact border growth function implementation is? I can't find it in the game files but some simple tests have revealed some oddities related to GAME_SPEED / the PlotCultureCostModifier. Here's some values I've pulled from the latest version on turn 1. These are turns to next tile (first tile) acquisition on Quick/Standard/Epic/Marathon. Any civ but Russia: 10/20/30/60 Russia: 10/15/20/45 First off, I thought the factor for Quick culture cost scaling was 0.67 but for some reason its 0.5 here which is odd, especially as the others line up with expected 1, 1.5, and 3 scalers. It certainly doesn't seem like the other Quick scalers for growth, building, tile improvements are 0.5, so this just seems like a mistake (I could be wrong though). Additionally, the Russian "-25" PlotCultureCostModifier doesn't seem to be applied consistently across all game speeds. On Quick the modifier is "0" and on Epic you're getting a "-33" instead of a "-25". This seems like an unintended consequence of applying era modifiers to border growth costs given the results, but I don't know the formula, so I can't inspect this further myself. Also just because its sort of relevent to this discussion, local_culture generated by the updated Epona pantheon doesn't show up in any tooltips so border growth estimates are currently wrong across the board if you have the pantheon. I'd be happy to report this all to Github as well if someone can verify this behavior is not intended.