I think Apocalypse has some really nice aspects. The new natural disasters are amazing (Especially the comet strikes), and I really like the late-game apocalyptic state the world gets in. The only thing that really bothers me is that the natural disaster slider is stuck on 4. I love the constant fear of my cities being destroyed by comets in a single turn, but I could do without volcanoes erupting and rivers flooding every 10 turns and constantly destroying all my improvements throughout the game. The gamemode also could have used a little more content, but the new resources and city-states in the DLC pack make up for this in my opinion.
Some other gamemodes:
- A world war event forcing every civ to pick one of two teams and fight it out. Peace can only be made after at least 25 turns on standard. The event could trigger randomly after the world reaches a certain number of turns. Conquering cities or defeating units could earn you points for your team. When global peace is achieved, the party with the most points could get all current diplomatic favor from the losing team evenly distributed among winning players.
- A third party threat to all civs, forcing them to work together. This could be in the form of a zombie/alien invasion, a stronger barbarian faction that can take over cities or even the return of the Huns from civ V as a barbarous npc
- I really like the concept of empires breaking into multiple smaller states / civil war mechanics that people have been describing in this thread. This is already kind of touched on with the loyalty mechanic, but free cities could be fleshed out a lot more.
Oriental Empires does this in a really great way. If you don't take enough care of your citizens, some cities may claim independence and become their own faction. An independent player that you can interact with.
In civ, maybe you could get a huge yield boost to your capital when part of your empire breaks off, since your empire is now much easier to manage, making splitting up empires not an insta-loss, but somewhat of a viable strategy. (essentially making the switch from a wide to a tall empire.) Of course then there's the issue with which leader the broken off part of the civilization would lead, but hey. We're all speculating and theorizing here.
- One of the things I miss the most from civ V are teams in singleplayer. With the addition of some new team-based mechanics this could be turned into a gamemode.
- And finally, a one vs. everyone gamemode inspired by the SuperShaka Challenge
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