There’s a joke that I made up a while back that goes like this:
What’s a Metaphor?
It’s for when the regular one isn’t big enough.
And that’s more than just a bad pun, because a metaphors can be powerful stuff. Using one pushes an idea beyond the original context and allows the creator to reach out and “borrow” from another, more common, chunk of human experience so that new experience can seem more familiar than it actually is.
Whether it’s a piece of fiction or an interface, there can be a tendency in entertainment of all kinds to let your metaphor try and do too much work. After all, when done well it’s an easy way to create that all-important “aha” moment in the mind of someone experiencing your work. It allows them to “get” what you’ve been going for, and avoid the dangers of having to actually explain it to them.
The danger is, if you take it too far, that your audience can become too aware of what you’re attempting to do. And once they make the connection they may decide you’ve become a poor shadow of the thing that you’re trying to borrow from.
In the interactive world your problems get big really fast if you decide to be too literal, because you’re trading in efficiency for “truth”. Gamers may be happier with an interface where you can click on different pictures of rooms in a house, rather than having to steer an avatar from room to room in order to select the next level, no matter how “realistic” that is. Not every game is Super Mario…