I am a pretty green Inform user, though I’ve written other forms of Interactive Fiction and MUD code in the past. While this works in Inform 7 Beta, I am worried that there’s a much simpler way of limiting ALL actions, even future actions, that involve reaching out and touching the unreachable. Help me see the obvious?
One thing you could look into if you haven’t is the interplay of regions and backdrops. You could make an Indoors region and an Outdoors region for example, and put the sky backdrop only Outdoors.
"Sky"
The Mountain is a room. The Field is a north of The Mountain. The Rock is south of The Mountain. The Cave is east of The Rock.
The World is a region. The Mountain, The Field, and The Rock are in The World.
The Sky is a backdrop. It is in The World. Thanks George.
In my case, I already had some regions. I think they can overlap, in which case this would work. I also didn’t mind someone referring to the sky in non-outdoor rooms, just in case I wanted to support it when in the presence of a window.
Not perfect but workable. I’m enjoying Inform so far, but I think that some things are missing from the documentation, or devilishly hard to find. For example, someone on the google group mentioned “unlisting” a rule, but I found only one example mentioned in passing but not demonstrated with syntax, buried deep in the documentation, and it didn’t use the word “unlist” anywhere. I’d point at it exactly but have since lost it again. > FLAIL ARMS WILDLY
I did try a backdrop to implement a street that the main character isn’t allowed to cross streets. I can’t think of any other IF I have played where a street isn’t a path but a barrier. 
Hi Halley!
I’m afraid regions cannot overlap, although one can completely contain another (see Ch. 3.4 of the docs). You can get around this limitation by creating kinds of regions, as in: [code]“Sky” by Mike Tarbert
An outregion is a kind of region.
The sky is a backdrop. The description is “It’s a lovely blue.” Every outregion contains the sky.
The Wilderness is an outregion. The Forest is a room in the Wilderness.
Deepjungle is an outregion. The Jungle is south of the forest. It is in the deepjungle.
test me with “x sky / s / x sky”.[/code] Note that in the above code the two rooms are in different regions but, because those regions are “outregions” (a new kind of region), they contain the sky. If you want to be able to see the sky in an interior room (such as through a window), these can be added on an individual basis. Backdrops can be assigned to whole regions, individual rooms, or combinations thereof (ch. 3.9).
Hope this was helpful! 
Yeah, I think I’ve used the word “unlist” before in posts too, since that’s how I think of it. The correct syntax is “not listed in” and described in ch. 18.4. - Listing rules explicitly:
Sorry to disappoint, but Aikin and Eve’s recent “Mrs. Pepper’s Nasty Secret” uses this very device in the opening. (BTW - not a spoiler, since it’s right at the beginning.)
So does A Matter of Importance by Nestor I. McNaugh (Valentine Kopteltsev). Only in the case of AMOI, it’s actually a puzzle you have to solve.