Z Axis

So, in order to represent a ruined, post-apocalyptic city, you need properly generated vertical maps, I'd argue.  I already had the generation part done some time ago (although it has a bug with doors past the first floor, as you may glimpse in the below GIF)

However, I don't plan to have inter-level interactions.  Although it might be realistic to have someone sniping at you from the second floor, it'd be frustrating from a game play perspective, as you don't have a true 3D view.  As demonstrated below, what I've done is made air transparent, and had lower tiles darken as they are further below you in Z levels.

After a bit of moving around, I move the camera up through the Z levels, and then down underground, below: