§3.5. Doors, Staircases, and Bridges
Inform's "door" kind provides for a tangible thing which comes between one room and another. A door can be open or closed, and openable or not: it can be locked or unlocked, and lockable or not. Here we create a conventional door, a natural gap in the rocks, and a (fixed in place) wooden ladder:
The fire door is an open door. The fire door is east of the Projection Booth and west of the Fire Escape.
The narrow crevice is an open unopenable door. The crevice is east of the Col du Prafleuri and west of Rocky Knoll Above Arolla.
The wooden ladder is an open unopenable door. The ladder is above the Stableyard and below the Hay Loft.
Most doors are visible from both sides: they are single objects but present in two rooms at once, which raises a number of complications. Inform normally uses the same description looking from each way, which is not very interesting: When? and Whence? demonstrate neat ways to describe the two sides differently, and Whither? adds the option for the player to refer to doors as "the west door" and "the east door" automatically.
Neighbourhood Watch goes further by making a door behave differently on each side: from the "outside" you need a key, but "inside" it opens on a latch. Finally, Garibaldi 1 shows how to access information about the two sides of a door.
Higher Calling demonstrates doors which automatically open as needed: though using the Inform extension Locksmith by Emily Short is probably easier and better. Elsie, conversely, demonstrates a door that closes one turn after the player has opened it.
Certain complications apply when characters other than the player have to see and interact with doors that exist in other rooms. Wainwright Acts demonstrates the syntax needed to handle this technically quirky situation.
Something Narsty and Hayseed provide a "staircase" kind useful for vertically arranged, always-open doors like staircases and (fixed in place) ladders.
One Short Plank implements a precarious plank bridge across a chasm as an open unopenable door.
See Windows for climbing through a window from one room to another
See Ropes for portable connections between rooms, much of the development of which could be adapted to handle portable ladders. "Doors" are never allowed to move
See Magic (Breaking the Laws of Physics) for a hat that lets the player walk through closed doors
See Modifying Existing Commands for ways to allow the player to unlock with a key he isn't currently holding
| ExampleWhen? A door whose description says "...leads east" in one place and "...leads west" in the other.
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| ExampleHayseed A refinement of our staircase kind which can be climbed.
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| ExampleHigher Calling All doors in the game automatically attempt to open if the player approaches them when they are closed.
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| ExampleWainwright Acts A technical note about checking the location of door objects when characters other than the player are interacting with them.
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| ExampleWhither? A door whose description says where it leads; and which automatically understands references such as "the west door" and "the east door" depending on which direction it leads from the location.
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"One Short Plank"
The East Jungle is a room. The plank bridge is west of the East Jungle and east of the West Jungle. The plank is an open unopenable door. "A precarious plank bridge extends [if the location is West Jungle]east[otherwise]west[end if] across the chasm." The description of the plank is "Extremely fragile and precarious."
Instead of going through the plank when the player is carrying something:
say "You step gingerly across the plank, which bows under your weight. But your meagre possessions are the straw which breaks the camel's back!";
end the story.
After going through the plank:
say "You step gingerly across the plank, grateful that you're not burdened.";
continue the action.
There is a feather in the East Jungle.
But indeed, why stop there?
The gigantic stone ball is a thing in the West Jungle. It is pushable between rooms.
Before going through the plank with something:
say "Surely you jest." instead.
Test me with "w / e / w / push ball e / e / get feather / w".
|  ExampleOne Short Plank A plank bridge which breaks if the player is carrying something when he goes across it. Pushing anything over the bridge is forbidden outright.
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"One Short Plank"
The East Jungle is a room. The plank bridge is west of the East Jungle and east of the West Jungle. The plank is an open unopenable door. "A precarious plank bridge extends [if the location is West Jungle]east[otherwise]west[end if] across the chasm." The description of the plank is "Extremely fragile and precarious."
Instead of going through the plank when the player is carrying something:
say "You step gingerly across the plank, which bows under your weight. But your meagre possessions are the straw which breaks the camel's back!";
end the story.
After going through the plank:
say "You step gingerly across the plank, grateful that you're not burdened.";
continue the action.
There is a feather in the East Jungle.
But indeed, why stop there?
The gigantic stone ball is a thing in the West Jungle. It is pushable between rooms.
Before going through the plank with something:
say "Surely you jest." instead.
Test me with "w / e / w / push ball e / e / get feather / w".
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|  ExampleElsie A door that closes automatically one turn after the player opens it.
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