I've been working on a (pen and paper) RPG system and currently using it for a zombie themed rogue-like called Survivor's Fieldbook, heavily influenced by MUD, Dwarf Fortress, and FTL.
Recently, I've updated how zombies and humans choose their targets. I've written it up on my blog, but the gist is: zombies are attracted to blood and loud noises and humans must be able to see the zombies to target them.
Here's an example:
the zombie in the building on the lower right is invisible to the survivors who wander aimlessly until one of them spots it
Bonus question: What gaming website do you most frequently visit?
Bonus Answer: reddit.