Disappearing Doors by Andrew Plotkin

Version 1

The ability to remove doors from the world and put them back.

The Standard Rules let you "change the (direction) exit of (room) to (room)", but doors are fixed in place on the map. This extension does not allow you to move doors around, but it does let you make a door disappear and then reappear in the same place.

This is done through a "present" (or "absent") property of doors. So you can write:

now the magic door is absent;
now the magic door is present;

if the magic door is absent:...
if the magic door is present:...

Doors always start as "present". If you want an initially hidden door to be revealed (a common case) then you must say:

When play begins:
     now the secret door is absent.

When a door disappears, it leaves no exit where it was previously connected. You can reconnect those directions to other rooms, but you must disconnect them before you make the door present again.

Making a door disappear or reappear does not affect whether it is open, closed, locked, or unlocked.

A one-sided door cannot be made absent. This extension only works on two-sided doors.

(This extension has been tested with Inform 6G60 and 6L38.)

A	Example The Prisoner of La-Z-enda A simple demonstration of an appearing door.