terraria
In Terraria game, we can build houses for NPCs. They must be at least 8×5 from inside, and surrounded by walls and blocks. It must also have a chair, a table and a door.
But… Can it have two doors?
Two doors can be convenient, so we can access the house from either side, or even walk past it.
In an answer* to a related question, it is stated that:
[A meteor] may not intersect with a Player, an NPC or a Chest.
If your house is only large enough for your NPCs, it's quite likely you're already safe. If not, as an alternative to making a skybridge barrier, you might instead make an "attic" full of chests. This will cause the game to look for a different location entirely rather than leave only a thin layer of meteorite, as a skybridge would.
**My understanding is that the rules listed in the linked post were determined by examining the game's code, but it wasn't done by me, so caveat emptor. ;-)*
Assuming that all of those have walls and a light source, those would count as valid housing. The requirement is that it has a door, not that the door go anywhere. Also notable is that wooden platforms count as doors for the housing rule, so you can actually just have a wooden platform separate the rooms from each other as well.
Here is an example of housing with internal doors:
If I can, then I'm going to be making pressure-plate/activator automatic doors that don't get torn down in a blood moon.
This is actually a very common strategy to defend from a blood moon. As noted in the Base Defense Guide on the Wiki:
By using actuators and Grey, Brown, Blue or Lihzahrd pressure plates, you can create a player only door that doesn't even require you to use your mouse. Setup the door as you would an active stone/actuator door and because Grey, Brown, Blue or Lihzahrd pressure plates can only be activated by the player no mobs are able to enter (nor escape).
You can also just place a torch or other item in front of the door so that it can only be opened when you are facing towards the outside. From the wiki:
Another way to prevent enemies breaking down your door is to place a non-solid object, such as a chest, wooden platform or other Furniture item, on the inside of the door. This will prevent enemies from opening it but will require the player to face away from the house to open the door.
Best Answer
The Terraria NPC houses only really care about the minimum requirements. You can go much grander if you'd like, for instance.
My Merchant actually lives in my dining room.
Three stories, two doors -- as long as it meets the minimum requirements, they'll move in. They ain't picky, either.