Adds more depth, fun challenges and chase goals for factorio addicts, especially in the later stages of the game. Intended to be a high quality vanilla+ experience and the ideal version to megabase on.
Stone walls requiring concrete leads to a weird situation where the purely red tech stone wall is gated behind the red/green tech concrete. If the intention is to make walls from concrete later on, maybe add the concrete recipe as an alternate unlock and keep the standard stone recipe but make it less efficient? Alternatively, move the stone walls unlock to the concrete tech or add green science cost to it.
