Especially with the concept of being able to breed resources. I mean if you buy horses from a neighbor, you should be able to have a farm that will grant you horses in the future. For instance, it could be like this: If you dont build any horse-based units in a 20 turn period, than the horses you bought will still be yours, and you can breed them from there on.
It should be like this with all animals and plants, and only the mineral kind of resources should be as scarce as the game makes them.
Other thing that I dont like is that you have to get your food in the nearby area. I think that the game should allow specialized cities, like, if you have an area of your countryland that is good for food, than cities over there will be farms and feed your whole civ. If an area is good for shields, than that will be an industrial zone.
Working that way, combined with the ability of setting the city purpose, youd be able to have an planned progress, and its more realistic, and not so hard to achieve.
But the thing that Id like to be changed the most is the way that roads works.
When you think of real wars, theres always thinks like key points. Take down that fortress, the foe is down. Take that city, they are history. But, in the way that movement works now, its unimportant what city you strike first.
How I think that it should be: Ok, in real life, you dont have countries that have railroads in each square, like it happens in civ. You have urbanized cities and connecting roads. So, I think that roads outside of the FAT X radius should be WAY more expensive, in the sense that its only worth to build them to link one city to the others, and limiting them as your way to be able to really move.
This, combined with giving back the road bonus to the foes (after all, the roads on Afghanistan do not disappear under the feet of the USA soldiers), would create a logical war path to the enemy forces, would justify the building of fortresses, as you would have stress points to defend, and would make surprise attacks much more interesting, like: Oh my God. They tricked me. I was waiting for them in my mountain road and they came trough the forest. Who could have guessed?
Finally, I think that colonies should survive in the culture zone of the other civs, and have a culture flip factor like the cities, even if smaller. After all, why should you build a colony in the other side of the ocean if you know that when the other civ expands minimally their cultural borders, they will absorb yours anyway?
Well, those are the most important remarks I wanted to make.
Regards

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