While a record 40 million people have tuned in to watch the third season of Stranger Things since last week’s debut, a smaller but impressive subset of the sci-fi thriller’s fans have been busy playing an alternate reality game based on the show’s themes of Russian espionage.

The game, Operation Scoop Snoop, began last week and features an “alternate universe of Russian spies, uncrackable codes and a mind-bending video game.” But there’s a catch: It can only be played with 1985 technology. And it’s sponsored not by the Scoops Ahoy ice cream store from the show, but by Baskin-Robbins.

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