The world has always had a layer laid over it.
The places you know best are the ones you've looked at least.
Most people pass through. A few stop.
Limn, explained.
It shows you that the places you pass are not fully known. You are standing somewhere that has been passed over more times than counted.
Nothing about the location has changed. But something about how you are seeing it has.
Panes are placed in the world. Finding one requires only that you are the kind of person who notices.
Where, now.
The first are placed in one corner of the city. Close together, easy to reach if you know to look.