Finally fixed.

Thank you. I'll take a look when I have time.

Found maybe a bug, in my actual game i can't build bulwark, even as no one else build it and my capital is build on top of diamonds:
https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=1569260991

Ok, so that's a bit of a mistake, there's only production in the city in which it is built. Thanks for letting me know.

Okay, found it :) but 2 things:

I have 3 cities, build it in a city and i see the bulwark symbol like on screenie 3.It states +2 production.

1) See this bulwark symbol in every of my cities, is that correct? Everywhere it states +2 production
2) i have 3 unused iron + 5 diamonds (one traded away) and 1 gold, so 8 / 4 = 2 is correct, when would it jump to +3 production? I mean 9, 10, 11 or 12?

Yes, click on the city in where it is built; see the third screenshot

Ah okay, thought a normal mine on hills would be enough :) that explains it :)

Can is see somewhere how much extra production i gain from it?

Should work with any resource improved by a mine, so: iron, coal, aluminum, uranium, gold, silver, copper, gems, salt etc.

Question: I used this bulwark wonder, i had my capital near a hill with a mine on top (1 field direct to capital) ... but can't build that wonder! What for resource is needed to be albe to build the bulwark?

If you have any suggestions for effects, I'd like to hear them. Maybe something with spies.

Hey that's a great idea, never crossed my mine lol. Thanks! :)

I don't know if you do requests but i think making cidhna mine is a great idea

Yes, exactly. And there will be a time where you won't have to use the 8 iron anymore, which means you'll get +3 Production. Currently, even traded iron will increase production, but I will change that (an oversight).

I think I get it now - If you have 2 mines with iron each and you are only using 8 iron you have 4 to spare get +1 in ciy built in

It counts from all in your empire, and only adds production to the city it's built in.

It works like this: for example, if you have 8 Iron you no longer use for anything, you'll have 8 'unused copies' of Iron. This means the city the Bulwark is built in gets +2 production. The ratio might be a bit too much. However, coal, aluminum and uranium are generally used and therefore would not contribute to the production bonus that much. Would like to know how it pans out in terms of total production added. Might have to rephrase it again to make sure it can only be interpreted in one way :P

Not sure I understand the 4 unused copies part could you explain please

So does it only count unused strategic resources from the city it's built in, or from all in your empire?