[BNW] Adding Building Count Limit for Players?

Hello guys,

How do I add limits to count of buildings a player can build? Example, a player can only build 10 Operas even if he has 30 cities.

and

I'd like to mod Promotions to do more bonuses but just couldn't get the text to say what it should. The pop-up text that says for example, "33% bonus attacking ..." or something like that. (mainly because I was editing the game's xml directly)


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About me:

I'm new to CIV 5 modding, have read quite a bit and got a grasp on the basic concepts. I've been doing the civ IV way for some weeks now, but now I know it's a big no-no. Also, I've been checking other people's work to see what they're doing and how they're doing it, but I just can't get adding limits to work.

I will be having a few more questions in the future regarding creating Scenarios like the mongol scenario or africa that comes with the game. I've read and followed a tutorial for this as well, but definitely need more info on this subject.

I'm also an artist, but currently incapacitated -- so to speak. Planning on helping the community soon, as I see a lot of good mods in development.

Thanks.