[lehall]

You’re probably thinking of the Latitude Society, by the creators of the Jejune Institute. Invites were given as blank white cards that would swipe you in at an anonymous building at an appointed time, kicking off the first part of the experience. https://nonchalance.com/latitude.html

There weren’t elaborate practical effects per se (there were some cool builds, like custom arcade cabinets) but many extremely talented experience designers worked on it so it felt very magical.

[uyt]

I think I was recalling the pepper ghost effect stuff.