So, I have a room with walls and the npc can walking inside of course. In the room there are solid block walls. That's why, the npc can't go through the walls, for exemple to the other room. But I (the player) can building doors on the walls if I want it. I would build walls where I want on the walls. (Otherwise it will be a top-view game). The problem is the npc won't go through the door because under the door there located the part of wall. The player can build the door anywhere on the wall.
You can imagine this situation as a problem of the river (as wall) and the bridge (door). I'd like to build a bridge above the river. Of course the npc doesn't go through the river and he's need a bridge. I can build a bridge anywhere part of the river. I was build a bridge but the npc couldn't walk through this, as the river stayed under the bridge and this one have a solid behavior and it overwrited the basic non-solid behavior of the bridge for some reason. I don't know why. The bridge on upper layer than the river.
I need a simple solution. I hope you understood what I want and the situation as well. Thank you!