Fortnite video game taking over world

Every few years a new video game fad explodes onto the scene. In 2016 it was Pokémon Go, now it's Fortnite.

The game has been downloaded more than 40 million times since its launch last year - but its popularity has prompted a warning about the dangers of addiction.

If you have children or even know a child, chances are you've heard of Fortnite. For those who have been living under a technology rock, it's a battle-royale, shoot-em-up video game.

"You just have to go around and try to kill people, so you're the last one standing," says Fortnite player Megan McCarthy.

The game pits 100 players against each other in a frantic fight for survival.

Megan and her brother, Hamish, are just two of the millions of Fortnite fans around the world.

"There's no blood so it's not actually too bad," Hamish says.

Hamish is a straight shooter. Megan's more about strategy.

"If I can, I'll hide in a tree until everyone is dead and then I'll come out and try to kill the last person," she says.

But no matter your skill level, the game will get you hooked.

"Fortnite is really addictive because it's a free-to-play game and it doesn't make any difference if you play it for one hour or 100 hours, you're always going to get the same experience," says video games journalist James Jarvis.

The game may be free, but players can buy accessories like costumes and dance moves. That alone reportedly made its makers more than $300 million in March.

Its popularity is so great the UK government has issued a warning, and that's prompted others to consider the dangers.

"So many parents think, 'Well at least they've got something they're passionate about,' but it can be like a drug, and it excludes them from being social and those types of things," says parenting expert Ian Grant.

It's not just playing the game that's addictive. Fortnite fans are also obsessed with watching people play.

As if the game isn't popular enough, it's collecting unofficial celebrity endorsements all over the place, from NRL stars mimicking the characters to basketballer Steven Adams boasting about a victory.