got it finally, looks like they're a very endgame thing...
Viewing post in When Civilians Dig Holes comments
hey thanks so much again for playing, im sorry that the late game is pretty unbalanced right now :-( im working my way through the game and adding the new hole locations so that eventually progression hopefully wont fall off so hard. I think in previous versions there was the opposite problem where the progression sped up way too much so I tried to balance it, but it seems like i took it too far in the other direction for the latest update. anyways thank you for posting your experience its all really helpful feedback for me !