At any place (room, or inside a container) light is either fully present or fully absent. Inform does not usually try to track intermediate states of lighting, but see The Undertomb 2 for a single lantern with varying light levels and Zorn of Zorna for multiple candles that can be lit for cumulative changes to the light level.
Light can be added to, but not taken away: rooms and things can act as sources of light, by having the "lighted" and "lit" properties respectively, but they cannot be sinks which drain light away. The reason darkness is not a constant hazard in Inform-written games is that rooms always have the "lighted" property unless declared "dark". (We assume daylight or some always-on electric lighting.) A "dark" room may well still be illuminated if a light source happens to be present:
The Deep Crypt is a dark room. The candle lantern is a lit thing in the Deep Crypt.
Hymenaeus allows us to explicitly refer to torches as "lit" or "unlit", or (as synonyms) "flaming" or "extinguished".
For light produced electrically we might want a wall switch, as in Down Below, or a portable lamp, as in The Dark Ages Revisited.
The fierce, locally confined light thrown out by a carried lamp has a quality quite unlike weak but ambient daylight, and Reflections exploits this to make a lantern feel more realistic.
When the player experiences darkness in a location, Inform is usually very guarded in what it reveals. ("It is pitch dark, and you can't see a thing.") Hohmann Transfer gives darkness a quite different look, and Four Stars heightens the other senses so that a player in darkness can still detect her surroundings. The first of the two examples in Peeled allows exploration of a dark place by touch.
It is sometimes useful to check whether a room that is not the current location happens to contain a light source or be naturally lighted. This poses a few challenges. Unblinking demonstrates one way of doing this, so long as there are no backdrop light sources.
Cloak of Darkness is a short and sweet game based on a light puzzle.
See Room Descriptions for an item that can only be seen in bright light, when an extra lamp is switched on
See Looking Under and Hiding for a looking under action which is helped by the fiercer brightness of a light source
See Going, Pushing Things in Directions for making it hazardous to walk around in the dark
See Electricity and Magnetism for batteries to power a torch or flashlight
See Fire for a non-electrical way to produce light
| Example Hymenaeus Understanding "flaming torch" and "extinguished torch" to refer to torches when lit and unlit. | |
| Example Reflections Emphasizing the reflective quality of shiny objects whenever they are described in the presence of the torch. | |
| Example Peeled Two different approaches to adjusting what the player can interact with, compared. | |
Suppose we're simulating a situation where the player needs to travel through lit areas only, but we want to give him some hints about which way might be safe. Here we'll find our best route through light-filled rooms.
The slightly tricky part is that it's not necessarily easy to tell whether a room has a lamp in it. We may say "if the Crypt is lighted", but that only tells us whether it has been declared to be inherently lighted or dark, not whether it happens to contain a light source that the player would be able to see if he went in.
The easiest way to get around this is to create an object -- the light-meter; place it in the target location; and check whether it "can see" a lit object. This preserves all the usual rules about open and closed containers, transparency, etc.
"Unblinking"
Section 1 - Procedure
The light-meter is a privately-named scenery thing.
Definition: a room (called the target room) is light-filled:
if the target room is lighted:
yes;
move the light-meter to the target room;
if the light-meter can see a lit thing:
yes;
remove the light-meter from play;
no.
That done, we're free to use our best-route phrases to choose a particular route.
Section 2 - Scenario
The Tomb of Angels is a room. "This ancient underground tomb is lightless but for a few shafts from the surface. Everywhere in the shadows are carved angels, their faces worn away by water and pollution, their wings little more than nubs."
The Upward Path is above the Tomb of Angels. It is dark. "The staircase switches back on itself many times as it ascends towards the Crash Site."
A container called the sarcophagus is in the Upward Path. It is closed and openable. "A sarcophagus rests in the niche here, [if open]the lid pushed aside[otherwise]the lid firmly in place[end if]."
The Crash Site is above the Upward Path. "The ceiling has wholly caved in here, and the belly of the spaceship above you is visible -- including the escape hatch."
A candle is a kind of thing. A candle is usually lit. The player carries four candles.
After looking when the location is not the Crash Site:
if the best route from the location to the Crash Site through light-filled rooms is a direction (called next way):
say "It looks like there's a safe, lit path [if the number of moves from the location to the Crash Site through light-filled rooms is 1]straight[otherwise]if you go[end if] [next way].";
otherwise:
say "It looks like there is no fully lit path from here to the Crash Site."
Test me with "up / drop candle / down / up / take the candle / open sarcophagus / put candle in sarcophagus / down / up / close sarcophagus / d".
An important word of caution: this method would give false negatives if there were a backdrop lightsource, such as the moon, providing light to the Upward Path. This is because backdrops are actually moved around the map by Inform during play, following the player around. So if the moon backdrop is in the Crash Site with the player, it will not be in the Upward Path as well -- even if it's scheduled to move there as soon as the player does.
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