Walkers has been entertaining shoppers in Manchester, U.K. with an interactive poster that invites people to make the shapes of letters with their bodies.

It's all part of a wider promotion by the Pepsico-owned snacks brand that invites people to collect the letters from special packs and spell a destination to win one of 20,000 vacations. The way it works is that if people can successfully form the letters, they can add those letters to their collection.

The poster uses bespoke technology combining touch-screen, real-time gesture recognition and machine learning to identify the postures replicating each letter. Participants are guided through the process with playful and humorous messages of encouragement.

The campaign, by AMV BBDO and digital production company Grand Visual, ran on May 9-10 in Manchester, and will be running again this weekend.