"Lana and Frank were attacked by two zombies while on patrol. Frank skewered a zombie’s head with a carving knife, killing it instantly."
This simple, relatively innocuous line is typical in Zafehouse: Diaries, but it’s the result of an astonishingly complex set of interacting systems. It’s not an overstatement to say that it’s the result of months of work to get a line like that in the diary.
Our key design goal with Zafehouse: Diaries is that the world - and the systems underneath - be consistent. If not, we’d have to fill the engine with too many canned events and hard-coded responses, or we’d need to go the other way and introduce too many random systems. The former would be linear, contrived and boring; the latter might be inconsistent, unpredictable, loose, and possibly hilariously so.
So let’s look at that line a bit closer. Lana and Frank are survivors, each with their own skills and abilities, and they may or may not like each other. They’ve been given an order to go outside the safehouse and patrol - but not attack - zombies. These zombies are actually in the town - we’re tracking every zombie in every square metre, so Lana and Frank are patrolling around and looking for zombies in the surrounding space around the house.
That they’ve been attacked shows that they’ve failed the job. This could be because it was a daylight, they were making noise, there were too many zombies outside, they were particularly terrible at patrolling, or Frank’s lingering prejudice against Lana’s homosexuality made him less cooperative. All this information is either known or can be predicted according to some kind of discernable probability.
So Frank got one of them with a carving knife - a carving knife he chose based on its effectiveness at killing zombies. Given that there were only two zombies in the immediate area, he was able to get a clean strike on the zombie’s head - not arms, legs, hands, fingers or feet, which are also modeled - but if there were more zombies, or Frank didn’t have the knife, or he was injured he may have been grabbed by another zombie, become infected, torn apart, or worse. Actually, there is no worse.
Lucky that carving knife was lying around at the house. What if it wasn’t there? Frank would have looked for something else. If there were no weapons, he would have looked at furniture. Maybe he could swing that lamp and use it as a weapon, or perhaps he’ll grab a stool. Desperate times.
And I haven’t even talked about other events, survivors or systems. Maybe Regina was trying to create some experimental traps and one of them misfired, hit Susie, who got annoyed at Regina, then they had an argument, which escalated into Regina throwing a saucepan at Susie, which missed, smashed the window that John was trying to barricade but was going too slowly because he forgot to bring that hammer he found at the warehouse a few days ago, creating an incredible racket and attracting streams of zombies. And Lana and Frank, armed with a carving knife, would be staring down a shambling horde.
We think this is the key to what makes Zafehouse: Diaries so engaging. The intertwining systems produce a lot of variety, but their internal consistency provides that strategic core. Each line you see is one of many possible expressions of the world’s state at a particular time and understanding the diary is the key to winning.