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http://www.ign.com/articles/2016/08/03/hidden-agendas-and-improved-ai-in-civilization-6

Hidden Agendas and Improved AI in Civilization 6
Our extended hands-on reveals rewarding new systems paired with a focus on creating more believable AI.
IGN
By Joab Gilroy   3 Aug 2016



The intention was for Gandhi to be peaceful to a fault. That the famous Indian leader would be near impossible to anger, to reflect his famous passive resistance philosophy. In Civilization, hostility was handled on a ten point scale, and to reflect Gandhi's pacifism his hostility would hover at around one or two on the scale.

The problem for Civilization players was, however, that if they caused global hostility to reduce all at once, Gandhi's hostility would drop below the lowest measure on the scale. And because the game didn't handle negative integers, Gandhi's hostility rating wrapped around to the other end of the scale - and it didn't land on back on 10. It wrapped around and made its way to 255, and Nuclear Gandhi was born.

This is obviously an extreme - and unintended - example, but when a warmongering Gandhi lands on your doorstep, you’re very much reminded that you’re playing against a computer, and something has gone comically awry. The Civilization series has always had trouble creating AI that’s comparable to playing against a human. Overseeing complex civic, technological and military concerns is tough, and adding in state relationship management into the mix complicates things further.

Civilization VI is tackling its AI head-on, refining and building on the series' systems to make for more believable opponents who can make more nuanced decisions. And to ensure the game doesn’t become impenetrable for the player, the team has a neat solution – delegation.


An Exercise in Feudality

City states were added to Civilization V to give the diplomatic victory condition a shot in the arm. Neutral mini-civilizations, they required players to complete basic quests to earn approval, which in turn would result in the city states inevitably voting for you as the world leader. It was a good place to start, but Civilization VI has bigger plans.

The quests are still present - kill barbarians invading your land, acquire sugar as a resource - but you no longer jockey for favour with city states using an obscured measuring system. Now you compete for city state influence with other Civilizations using envoys. Envoys are earned by completing city state quests and through civic-related goals within your Civilization, and you get bonuses depending on how many you assign to each of your diminutive neighbours. Having one envoy with each city state is wise, because you get basic bonuses no matter what. Nan Madol in Micronesia, for example, might give you +2 culture in your capital just for establishing contact.



Bows, arrows and catapults... all you need, right?


The real bonuses begin when you establish at least three envoys and maintain more envoys than any other civilization. Becoming the suzerain - or feudal overlord - of a city state gives you huge bonuses, turning the city state into a vassal that you can call on for military might while still operating autonomously. And their bonuses are typically historically significant - to use Nan Madol as an example again, the famous coral city of Micronesia could give you +2 culture for every district adjacent to a coast tile, which is a huge boon if you started near a body of water.


“Becoming the suzerain - or feudal overlord - of a city state gives you huge bonuses, turning the city state into a vassal that you can call on for military might while still operating autonomously."


The suzerain system is sort of genius, because it feeds into the diplomatic playstyle so heavily. In Civilization V city states were useful for small bonuses from quests, but their focus was on spreading the world leader vote. Conflict around city states typically only arose towards the end of the game. Thanks to suzerain bonuses, conflict with other Civilizations can spring up in a moment. Imagine those pesky Egyptians take away your suzerain status with Kabul, where you were earning double military XP in battles you initiated. If the bonus was critical to your ongoing strategy - say you were waging a military campaign against a reluctant enemy and you were using Unit promotions to mitigate healing downtime - taking back suzerain status from Egypt becomes a high priority objective.

The diplomatic scene in Civilization VI is much richer as a result of this delegation. While Civilizations still manage their diplomacy based on their relationships with their opponents relative to their end game goals, the bonuses involved with establishing strong ties to city states disperses the pressure. And it can also give you handy information about a civilization's goals. If they fight tooth and nail to hold onto suzerain status with the scientific city state of Geneva, they might be working towards a research-based goal (and you can disrupt their efforts by declaring war on them, which negates Geneva's suzerain bonus).

 
Hidden Agendas

Diplomacy is more than just city state interactions, of course. As mentioned in an earlier preview hidden objectives play a massive role in driving the AI.

"We've got these big characters, these leaders with big personality types, and they're playing the game in distinct ways," Sarah Darney, Associate Producer at Firaxis, tells me. "Their historical agenda dictates how they navigate the game field. It gives them a familiarity when they play. 'That's Catherine [de Medici, French Leader], so I know I need to look out for spies.' With the hidden agendas that mixes things up. It adds another level, which means you want to be friends with everyone, or at least learn something about them through espionage."



A little light espionage.


I can confirm the secondary hidden objective hinted at by Lead Designer Ed Beach is not being implemented - Civ VI AI will have just the one hidden objective that players can reveal by building a strong relationship with them. The hidden objectives make diplomatic interactions a dynamic guessing game. In my hands-on, Cleopatra of Egypt was doing her best to make every nearby city state a thing of the past. She'd pause occasionally to remind me that my civilization, lead by Pedro II of Brazil, was weak. It seemed like her hidden objective was to make as many enemies as possible.

Meanwhile Theodore Roosevelt had a different hidden objective. If I had to guess, it would be to establish and develop the city of Baltimore and then to trade it to the glorious Civilization of Brazil for a book you can now get for free on Kindle. Because towards the end of my play session, the 26th President of the United States did exactly that, trading Sun Tzu's The Art of War for the place dubbed "The City That Reads" without a shred of irony.

It was probably a bug, to be fair. Civilization has a storied history of amusing bugs, after all, and we were playing pre-release, very much unfinished game code. It's about increasing priorities for the AI. From its humble beginnings in the first Civilization, where AI operated on a 10 point anger scale, Civilization VI has your opponents making decisions against a handful of systems for diplomacy alone.


Civically Minded

Outside of diplomacy, the AI is more complex. Decoupling the civic research tree from technological research makes things significantly easier for humans to manage, because there's no longer a need to choose between researching better government over military might.


"You no longer need to delay researching the next step in your cultural victory scheme in favour of 'keeping up with the joneses' who are researching advanced military technology."


As a player, you no longer need to delay researching the next step in your cultural victory scheme in favour of 'keeping up with the joneses' who are researching advanced military technology.

Initially the civic system is tough to understand. While your civilization is in its infancy, your options are limited. You can implement just two policies to direct your government, and the policies at hand are limited as well.

Eventually you get to broaden your government into something with a wide range of policies. Military, economic, diplomatic and wildcard policies allow you to structure a system which works for your playstyle using the policy cards system. Picking a form of government with many military card slots will give you powerful options when it comes to warfare, but your production and trade options might be limited.



Do your civic duty!


As the Brazilian empire I had a cultural advantage. The street carnival district increases happiness in Brazilian cities by increasing amenities without being tied directly to local resources. It replaces your entertainment district with a super-powered, Brazilian-themed one. With happiness no longer a global element, I was able to boost my cultural building blocks and pursue civic rewards.

While these changes - once properly understood - make things easier on humans, the AI has an even greater hill to climb. In Civilization V there were certain correct technology paths to take which simplified the priority handling of the AI. With a split tech and civics tree, governmental policy cards and city-independent happiness, the idea of an optimal path can change on a turn-to-turn basis, which means the AI needs to take more into account to keep up.


Warriors Come Out And Play

Turning to the military side of the game, the AI here has significantly improved in Civilization VI. Even the barbarians are more complex. Instead of simply roaming around the continent looking for civilizations to harass, barbarians now send out scouting units. They'll look at a few different civilizations, then head back to their encampment - and if they make it the barbarian AI will send a war party after the weakest looking opponent.

Barbarians stole settlers from me twice during my playthrough. Only one of those times was due to my own bone-headed idiocy. You can assign a military unit to your vulnerable units, and I placed a sling-thrower with my settler, determined not to send a settler out for easy capture a second time. Once I was out-of-range of safety, the barbarian AI ambushed my group with three warrior units and snatched away my settler, forcing me to once again chase after the extremely valuable city-building unit.



Comin' atcha like Cleopatra.


City states wage wars between one another and with civilizations, and I watched as the warmongering Cleopatra of Egypt encircled Nan Madol and barraged it with endless waves of warriors, horsemen and chariots. As the suzerain of La Venta, she was able to draw on their military resources to help defeat the Micronesian neutral - and when I sent enough envoys to La Venta to become suzerain myself, she declared war on me. Because districts spread out from your city, border management in Civilization VI is much more important. With my capital closest to her own borders, she marched in and began destroying improvements I'd made in my city. I'd placed my military district in a terrible place (it was my first game, go easy) and so when I purchased new units they were in a strategically awful position, which gave Cleopatra ample opportunity to wreak havoc throughout my capital before I could push her out.

The AI was tactical, too. Ranged units attacked from behind melee units, forcing me to take damage before making my way to her more vulnerable targets. The cost the city of Baltimore was putting on my civilization made it difficult for me to use gold to replace units, which gave her ample opportunity to ruin a trade-route France had set up, destroying the road as I attempted to force her out of my land.


With help from La Venta and Nan Madol, I would have eventually pushed her back, and because she'd spent so much of the early game committing resources to her war with Nan Madol I probably could have beaten her. But even on the low difficulty setting we were playing the preview code on, she made her way to my doorstep. And this is where we see the strength of the AI shine through - at this point Cleopatra had overextended, and it would cost her dearly. After all, believable AI needs to be capable of making mistakes for players to exploit.

AI in 4X games is always a juggling act. As the turn count increases, more items are thrown to the juggler, and the AI struggles to keep everything up in the air. In Civilization VI, the game is throwing everything it can at the AI, and from my 150 turn session with the game, it seems to be handling it.

Mixture of new and old screenies and videos at link, will try to find later.  [Good luck with the videos - non-YouTube versions.]