I’ve recently introduced my girlfriend to a little game called Civilization 4. Having sunk countless hours into both it and its predeccesors over the years, I’d put the game down in favor of more recent fare. While the game is not really new, I’ve been thinking more about design than I was when I first picked it up, so I thought I’d walk through some of the thoughts I’ve had in the last couple of weeks.

Civ4 has what you might consider to be a rather steep learning curve. There are a lot of concepts to grasp: How combat works, the rules governing production, finances, research, health, and culture, trading, exploration, terrain effects, religion, corporations, great people, resources; The list continues on and on. This list of concepts adds a significant level of complexity to the game.

Sid Meier once defined fun as ‘a series of interesting choices’, and that’s reflected greatly in his most famous series of games.  While the strategic complexity of Civilization 4 is high, the game is broken down piecemeal into a series of reasonably intuitive choices.  When your turn begins, the game will cycle through all the cities that need attention because whatever they were building has completed, and it will ask you what the city should build next (while recommending some of the best choices for that particular city’s current conditions).  Once that’s done with, the game cycles through all the units you control that are awaiting orders, the scope of which are reasonably straightforward, move to a different location, or perform an action, or even simply ‘automate my activity’.  If you’ve finished researching a new technology, the game will ask you what technology you want to work on next, or show you the tree that demonstrates what the impacts of each choice will be.

This series of simple, but interesting decisions form an emergent gameplay which is highly sophisticated.  When you add in the dynamics of interacting with other players, the result is a highly entertaining game.  This is why the Civilization series is a GOOD game, but not why it is addictive.  Those roots lie in a fundamental result of these simple choices.

Anyone who’s played a Civ game is certainly aware of the “One More Turn” phenomena.   These games are impossible to put down.  There’s no clock in the game, because time is piecemeal, so by the time you manage to exert some form of self-control, you look up from your computer, bleary-eyed, and find that it’s now 3:45am and you’ve just been game-locked for the past 6 hours.  I loved Bioshock and Portal, but they don’t give me the itch the way Civilization does, because those games don’t have a pound of pure psychological crack built into their framework.

The key to the addiction in Civ is I believe delayed gratification.  As I’ve discussed before, addiction comes from giving the player food-pellets (which are rewards of some kind) at frequent, but not regular, intervals.  There is something about the irregularity of the pellet reception that triggers certain psychological mechanisms that rhythmic reward does not.  In Civ there are several types of rewards going on, and there are a myriad of factors that go into the determination of the time between requesting the reward (beginning the production process) and the reception of said reward.

Because you have several cities, each producing something to bequeathed at a later time all at once, your subconscious brain is not able to grasp a pattern behind the frequency of reward, even though you can clearly see how many turns it will be until you get a pellet.  This is compounded by the fact that you have a lot of things to do each turn, so there is a significant amount of time that occurs (usually minutes) between movements of the clock forward.  The amount of real-time that occurs between turns is not consistent however, which again adds to the irregularity of the pattern.

Every time something completes, you can literally feel a small jolt of excitement, at which point, like a drug addict who’s becoming resistant to his favorite hit, you immediately request your next jolt, but you’ve got to wait for it.  Not too long mind you, just a few turns, but with so many of these activities going on at once, you’re going to get another hit in just one more turn, until it’s 3:45am and your cat is yelling at you to get out of his chair so he can go to bed.