| Chapter 3: Things |

| 3.12. Doors

The map of an interactive fiction is the layout of rooms and the entrances and exits which connect them. So far, these map connections have always run from one room to another, like so:

> The Painted Room is north of the Undertomb.

However, we can also interpose doors between rooms, like so:

> The heavy iron grating is east of the Orchard and west of the Undertomb. The grating is a door.

The second sentence is needed since otherwise Inform will take "heavy iron grating" to be the name of a third room, whereas what we want is for the grating to be something physically present in both the Orchard and in the Undertomb, and acting as a conduit between them. To this end it needs to be a "door", a kind we have not so far seen. In the absence of any other instruction, a newly created door will be fixed in place, closed and openable.

The grating really does come in between the two rooms: the grating is what lies immediately east of the Orchard, not the Undertomb room. So if we wrote the following:

> The Undertomb is east of the Orchard. The heavy iron grating is east of the Orchard and west of the Undertomb. The grating is a door.

then Inform would say that this is a contradiction: we said the Undertomb was east of the Orchard, but then we said that the grating was east of the Orchard.

Inform's "door" kind can be used for all manner of conduits, so the word door need not be taken literally. In Ursula K. LeGuin's beguiling novel "The Tombs of Atuan", from which the above rooms are stolen, it is not a grating which interposes, but:

> The red rock stair is east of the Orchard and above the Undertomb. The stair is an open door. The stair is not openable.

In real life, most doors are two-sided, and can be used from either of the rooms which they join, but this is not always convenient for interactive fiction. Here is a one-sided door:

> The blue door is a door. It is south of Notting Hill. Through it is the Flat Landing.

(Note the use of "it" here as an optional abbreviation.) This will make a door visible only on the Notting Hill side; no map connection will be made in the reverse direction, unless we ask for one.

Should we ever need it, the values "front side of ..." and "back side of ..." reveal where a door is placed. (For instance, "front side of the heavy iron grating" is the Orchard.)

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| Example Disappointment Bay 5 Disappointment Bay: adding the door and the deck to our charter boat.

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| Example Escape Window that can be climbed through or looked through.

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| Example Garibaldi 1 Providing a security readout device by which the player can check on the status of all doors in the game.

Suppose we would like to allow the player to view the status of all the doors functioning in the game; and we want to identify those doors by mentioning which two rooms they connect. The following uses some techniques that will be covered in later chapters, but the basic idea may be obvious: "Garibaldi" The security readout is a device. The description of the readout is "The screen is blank." Instead of examining the switched on security readout: say "The screen reads: [fixed letter spacing]"; say line break; repeat with item running through doors begin; say line break; say " [item] ([front side of the item]/[back side of the item]): [if the item is locked]LOCKED[otherwise]UNLOCKED[end if]"; end repeat; say variable letter spacing; say paragraph break. It is more or less arbitrary which room winds up as the "front side" and which as the "back", but in this case it hardly matters. The player carries the security readout. The Docking Bay is a room. The inner airlock is a door. It is north of the Docking Bay and south of the Zocalo. The inner airlock is lockable and unlocked. The outer airlock is lockable and locked. It is a door. It is south of the Docking Bay and north of Space. The quarantine seal is a door. It is west of the Zocalo and east of Medlab. Quarantine seal is locked. The security pass unlocks the inner airlock. The player carries the security pass. Test me with "x readout / turn on readout / x readout / lock inner airlock with security pass / x readout".

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