Tech costs base on number of entities

[wowgetoffyourcellphone]

Would be good to add feature for techs, where costs can be per number of certain entities. So, a "Stone Towers" upgrade that costs various amount of stones depending on number of wooden tower the player has built so far (so, like 25 stone per tower). Another example would be "Spies" or "Espionage" tech that reveals vision of enemy units, cost per enemy unit (like 10 metal per enemy unit). Anybody have any other examples where this would be usefull?

Edited June 19, 2015 by wowgetoffyourcellphone

[wraitii]

I think your stone tower example would work better with individual upgrading and an option to ugprade all. But I agree that it might be useful.

[WhiteTreePaladin]

BFME 1 and 2 handled upgrades that way; it made it more painful to lose troops / buildings. I think it works much better for battalions; it would probably be too much effort for individual units (keeping track of which were upgraded, etc.) even if you selected a group of them.