Fortnite has generated revenue of more than $300 million in a month. It is free to download but players can buy costumes or dances to stand out from the crowd

After planting a header into the back of the Swedish net, Dele Alli wheeled away from his team-mates in jubilation. The England midfielder then paused, jiggled his hips and waved his hands about his head in a circular motion, as if holding a lasso.

To anyone over the age of 25, his celebration was baffling. To everyone else, it was obvious: Alli was performing the “Ride the Pony” dance from Fortnite, the world’s most popular online game.

Since launching last September, Fortnite has become a cultural phenomenon, a craze that has transfixed a generation nurtured on smartphones and Instagram. To their parents and teachers, the game is a cause of anxiety, not to mention endless conflict over screen time. Think of it as the