Well ... to make it even more difficult ... for those who want "fog" ... how 'bout parts of the map, that shows what you've explored, have a chance of disappearing if the map gets wet?
Walk through a stream, or stay out in the rain ... and parts of your map "run".
Now that we're getting into absurd details, can there be an option for insomnia?
Or sleepwalking?
Or narcolepsy? Suppose, for example, we have a tendency of falling asleep at really inappropriate times and in really inappropriate places?
Certainty: a character-driven, literary, turn-based mini-CRPG in which Vasek, legendary "Wandering Philosopher", seeks certainties in a cryptically insular, organic, critically layered city.