Game worked just fine until I had about 150K buildings and was expanding my foundations. I currently have 757K buildings, and I have to play at 3-6 FPS, even with graphic settings to 'Minimum' option. I was able to play at with 'Maximum' settings until this point, and would consistently get over 30 FPS.
Additionally, saving the game takes on average 15 seconds, and fully locks up the game, to the point if I click in the game, it says shapez2 is not responding, then comes back.