So, I've got this setting. It's a supernatural post-apocalyptic story involving guys with superhuman abilities traveling across an America that's become a grid of 2x2 mile "squares" (technically pillars getting bigger going up and smaller towards the earth's core), each governed by a different supernatural gimmick. One square might make people fall west instead of down, another might make it impossible to tell lies, another might start to mutate you into some kind of human-badger hybrid the second you step into it. The people who have survived one year into what's come to be known as "Gridfall" have established settlements in the least dangerous squares they can find, learned as much as they can about the other squares surrounding them, and worked out the safest paths from one settlement to the next.
This, naturally, means that maps will be made that take the new grid system into account, and will need to inform the reader of what exactly they need to look out for with regards to the rules or gimmicks of each square they pass through. That's a bit tricky though, because conventional maps generally don't supply that kind of information. Maps generally work with symbols and coded lines, things that can be easily explained in a simple map key on the side of the map, things that barely even take a few words, let alone whole sentences, to explain. But these maps are going to have to say things like "people become half a foot tall in this one, but the animals stay the same size as always", or "people spontaneously combust at random when they enter this one, avoid at all costs. And keeping in mind that this is the post-apocalypse, where resources are scarce, they're going to want to come up with the most efficient and straightforward method of conveying this information as possible.
What would be the most efficient way to make a map of an area that also explains how all the squares in that area work?