Apologies about the server going down today. I just turned on my monitor to be greeted with a login screen... That shouldn't be happening.
Anyhow, I should hopefully find a host soon enough, and more importantly get back to work on my door system, and then perhaps heights.
Here's an issue with the z-level, though:
You are in room 0,0,0. It is aboveground.
Imagine that to the north is a hill. The top of this hill (represented by a single room, as it is a rather small hill) is one z level above you and one tile to the north. To walk up the hill, you would type "nu" or "northup."
Now, imagine that you type "dig n" and wait a short while for your character to finish digging a hole into the side of said hill. Now, typing "n" would place you inside an underground hill in the room. You could still type "nu" to climb up to the top of the hill, though.
You are now in 0,1,0, which is underground.
Now, getting theoretically theoretical, if you were to dig up from this room you'd have a nice staircase up to the top of the hill, but we won't imagine that we do this.
The description of the room you just dug reads something like, "This is a small, cramped tunnel underground. The walls are hardened soil and tree and plant roots penetrate the room at random intervals. Light shines in brightly from a hole in the south wall."
Let's say you then type "dig eu," which would dig an exit to 1,1,1 (1 up and 1 to the east). This is a sky room, thus if you attempted to use this exit, you'd end up in the air above the room to the east and fall one z level, probably bruising something. This doesn't make much sense.
How, then, should I handle this scenario? Should I not allow the digging of exits which lead to sky rooms? Why not? Digging a hole in the side of a cliff make sense, but somehow digging up and to the side out of a hill, resulting in a magical portal to 10 feet above the ground, doesn't sit well with me.
If anyone needs it, I can supply a drawing to help illustrate, though perhaps a 3d model or something might do a better job.