Thanks, jay... though it's not a vitally important thing, so if you're happy to investigate for the enjoyment of it, then go for it, but don't create work for yourself on my behalf!
For me, there are two ways the map on/off could work logically, depending on the way it's being done:
1) USER toggles it off:
- map should be drawn all the time, whether or not it's showing
- if map is turned on, map shows everything that has been discovered, regardless of whether it was found when map was on or off
- so it's just a .visible = true/false toggle as part of the game interface
2) GAME toggles it off:
- as if the hero of the story is drawing the map as he's going along, and when map is on, it's because he's drawing it himself with some paper, but when it's off, it's because he's running desperately through the forest, too quickly to keep track of where he's gone, and can't draw it, or even look at it.
- so it's actually more part of the game itself
I think (2) could also be achieved with non-directional exits? Or "move player" rather than using exits? Not sure.
What I was actually wanting though was (1), with the same incremental discovery as usual.
If it's not possible, then never mind, I'll leave the map on and people will have to live with it if they don't like it

psy