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thx.. that sounds a bit complicated and not directly obvious.. I mean charging should maybe cost coal and/or uranium because of the energy necessary.. but why should a shield charge decrease mine production?

The shield generator is there to prevent stealing of resources. If you are under constant attack you should still be able to use the shield generator. You would not be able to pay for the shield generator with resources if you are constantly looted. Thus the resources is taken from the income instead to always allow usage of the shield generator even if you are under constant attack.

OK.... makes sense.. THX for your reply