Paradox Development Studio's Crusader Kings II has been one of the surprise critical hits of the year, garnering attention and sales beyond what might be expected after a dozen Europa Universalis-style grand strategy games. I'm one of those critics, having reviewed it positively, and then only grown more impressed with its systems. What makes Crusader Kings II special and deserving of this praise is that it successfully models historical human behavior using a transparent system.

When Paradox offered me the chance to interview Crusader Kings II's project lead and designer, Henrik Fåhraeus, I took it in order find out just how this had been accomplished. Modeling human behavior within complex systems is one of the great dreams of video games (just ask Chris Crawford). Crusader Kings II, almost out of nowhere, impressed me by "...[building] a system that effectively simulated the power dynamics of medieval dynastic politics, and then [forcing] me to engage with and learn just how destructive those systems could be." How was this accomplished?

My expectation, built on years of developer interviews stressing the hard work of game creation, was that Crusader Kings II's success came after meticulous planning as well as constant testing and tweaking. But what came across in the discussion with Fåhraeus was something different: the power of serendipity and improvisation in creating a great game system.

Influence

I asked Fåhraeus about the influences and goals for the project, and he gave two main motivators. First, Crusader Kings II was another evolutionary step for the team.

"It was more a matter of taking all the similar systems we've developed at Paradox Development Studio over the course of multiple games (Europa Universalis, Crusader Kings, etcetera) and trying to find a better, unified way of realizing the same thing, with the added requirements of a character based game."

Paradox's commitment to pushing the Europa Universalis game engine to its limits is both slightly bemusing (it was clunky enough when it debuted over a decade ago) and impressive in how much the team seems to be succeeding.

He also mentioned a few games as influences, saying that Crusader Kings II "...(drew) inspiration from various spiritual ancestors; some relatively obscure, like The Lords of Midnight and Birthright: The Gorgon's Alliance and others not so obscure, like The Sims."

I think he may overestimate the degree to which people would see the breezy suburban modernity of The Sims as comparable to the epic medieval scope of his game; still, it's definitely there. You build relationships with your peers by giving them gifts and building the kingdom's infrastructure in a manner conducive to happiness. Instead of paintings and refrigerators, you ensure that dukes possess the counties that form the traditional bounds of their duchy, and if that's not enough, you can grant them ceremonial titles like "Keeper of the Cups." The goal is still the same: encourage the people that you interact with have more positive than negative relationships toward your character.

There were also era-specific considerations. "Of course, we wanted intrigue and vicious backstabbing in Crusader Kings II, since it was so sordidly common in real medieval history. Novels like the A Song of Ice and Fire and Dune books (both of which I love) only reflect reality."

That Game of Thrones connection, as mentioned by several critics, is quite clear in the game, and CKII quickly spawned a detailed, high-profile Game of Thrones mod. Fåhraeus's specific example: "Conan II, Duke of Brittany at game start in 1066, was murdered with a pair of poisoned hunting gloves, probably on the orders of William the Conqueror." With this sort of event as the model, the goals of the game become clear. "In order to facilitate this, AI characters especially needed to have clear opinions they could act upon."