In Defence of Enterables

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Kevin Forchione

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May 18, 1999, 3:00:00 AM5/18/99
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I put this before you, my fellow colleagues, that the enterable has been
much maligned. It has not yet had its day. Indeed, no game has yet had the
pleasure of an enterable to grace its stage. Yet, with the coming of the new
Millennium (and TADS 2.4.0) they are now among us...

The Appearance of Extension in Space
-------------------------------------------------------

Text adventures have several mechanisms for creating the illusion of an
object's extension in space. Chief among them is the use of descriptive
prose that engages the player's imagination to flesh out the details of a
world that exists primarily in the mind and only secondarily through the
mechanics of simulation. Just as the willing suspension of belief can turn a
stick into a sword or a raggedy old doll into a childhood companion, so the
well-chosen word has the power to mesmerise us, and beckon us into other
worlds.

Beyond description, however, the game enhances the illusion of
spatial-extension through accessibility rules. These are, in general, the
rules which govern what can be seen and what can be taken. They form the
frame upon which the canvass is spread, for they span the gulf between the
player's command and the all-alluring prose which form his meat and wine.

Extension and the Enterable
---------------------------------------

An enterable derives its primary behaviours from the openable and room
classes. This imposes a complex set of problems for the author, since the
two classes are radically different from each other.

Rooms present extension through stability. They cannot be taken, and
normally allow access only to the objects within them. They can be lit or
unlit, and though they cannot be open or closed they provide a nexus to
other objects through their travel-direction properties. Chiefly, they are
actor-oriented, providing complex mechanisms to provide the actor with a
sense of perspective from within themselves.

Openables do none of this. They can be taken, opened and closed, and most
importantly offer only a one-way perspective to the player. They are meant,
as it were, to be acted upon from the outside. While it is generally not
possible to reach into one room from another, no level of nesting of
openables is a barrier as long as they are all open. Thus they offer no
notion of depth beyond an inside and an outside and it is no more difficult
to extract an object from one openable as it is from a hundred nested
openables.

It is not even possible to say whether an openable is lit, because they do
not possess this attribute. A lightsource within an openable may grant its
blessed radiance to the surrounding room, but the space within the openable
is still filled with primordial void.

What is the author to think then, when she encounters an enterable? Surely
she will say, "My God! Why not use a room, certainly a nestedroom will give
you what you want!"

Well, what can be said? It's true that you can nest a room one inside
another. It's true that you can add the little open and close methods, the
verification and action methods, from an openable, if you wish, and
re-arrange the board and unboard methods to allow you to go in and out. But
no! I say it is not enough. What can we see? What can we touch? For pity's
sake, do not close the room!

"Well then," she will say, "Why not a nestedroom? Why look what they have
done! Do we not now have beneath us theFloor? Why not take a nestedroom and
add your little open and close methods?"

One looks to these things, in the beginning, when one is young, naïve, and
full of hope. We go inside, the torchlight of Prometheus in our hand,
lighting up the darkened sky, and tentatively we close the door. Sitting on
our room we gaze outward with amazement and then the torch slips from our
grasp and rolls into the outer darkness.

It has been tried. Many times. At last, we say enough! We put away our
childish dreams and walk the darkened streets of night alone. And so too
pass the years. But the enterable is in our mind alive, and somehow in the
darkness of the shadows it has grown, grown until at last our fevered hands
take to the keys once more. At last it's done! I can retire.

And so I sit with pen and pad to hand, sketching the sunset from the vantage
of my tent. And as the darkness falls, pull close the flap and set the
lantern down to curl within the cozy depths of my sleeping bag. And dream of
adventure.

What's Different?
------------------------

But how is it, you say, that the enterable is different from a room or
nestedroom? It is true that it displays a statusline, and that this
statusline resembles that of a room when the enterable is closed and that of
a nestedroom when it is open. It is true that you must get in and out of an
enterable, just as you must a nestedroom and that directional commands will
give you an error message.

Also, unless transparent, the enterable when closed must be lit from the
inside, like a darkroom, but when open receives its light from its location,
like the nestedroom. All of this has been well documented.

But there is more. What can I see? What can I touch? Sitting in my tent I
can enjoy the view of the meadow outside. Nestled inside my sleeping bag the
contents of my tent are plain to see, but beyond the open tent flap I can
see nothing. But in my hands I have a large plastic bag, perfectly
transparent. If I climb into this bag I can see not only the contents of my
tent, but the beautiful meadow beyond. Yes, the enterable can do all of
these things!

Those outside my little tent can reach nothing at all of its contents. They
must enter before they can take anything. Yet from inside my tent I stretch
forth my hand into the meadow and take any little thing in my reachable
list, just like a nestedroom. But from my sleeping bag, I can only touch the
contents of my tent, my reach is not so far. Yet with one attribute alone I
could configure a hundred nested enterables that allow me access to their
deepest contents with the ease of any openable, or stand nestled deep inside
them, reaching outward into the heavens.

The enterable class has behaviours similar to those of rooms, nestedrooms
and containers. These behaviours work in both directions: when access is
restricted inward it is also restricted outward, giving the illusion of
depth; when access is not restricted inward it is also not restricted
outward, giving the illusion of shallowness.

This class can easily accommodate other class inheritances, such as
fixeditem and transparentItem, allowing you to construct a variety of
enterables. Objects such as tents and sleeping bags are easily made, so you
too can go camping and enjoy the great outdoors beneath the stars.

Enterables, coming soon to an archive near you!

--Kevin

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