Raking in an estimated $318 million a month, blockbuster video game "Fortnite" is no child's play.

With a few tweaks on a classic "last man standing" battle royale, it's managed to suck in more than 3.4 million players and upend an entire industry. Added to that, kids in real life can't stop doing dance moves they learned from playing the game.

Set on a post-apocalyptic tropical island, "Fortnite" has 100 players from around the world skydive into a kill zone where they duke it out to be king of the hill, with guns, grenades and crossbows. In a popular twist, the map gradually shrinks to force the players into contact.

One of the secrets to its popularity is its low barrier to entry. The game is free to play and users can keep playing their same character from console to handheld device to computer. Players can express themselves by purchasing skins that change how they look or buy upgrades that earn them bragging rights with friends, who they can talk to, and, of course, taunt, throughout the game via headsets.

“It's not just kids living in their parents' basements. 'Fortnite' offers a very cartoonish aesthetic in a casual environment and because of that, it reaches a bigger audience,” Joost van Dreunen, CEO of SuperData, which supplied the estimates of the monthly revenues,told NBC News. Epic Games, makers of Fornite, didn't respond to a request for comment.

“Just as picking Pokemon was a form of expression for 14 year olds... You get to decide whether you’re a serious sniper or a clown running around in bright pants," he said.

And the micro-transactions fueling those options in "Fortnite" are driving big profits.

In another business model twist, the game has "seasons" where players compete to unlock a new set of themed achievements, some of which have to be purchased.

The game's popularity is even visible in the real world.

As part of a marketing stunt, there’s a llama sticking out of a phone booth in London. A "Durr Burger" mascot was found in the desert in California. And chances are, you’ve seen plenty of people doing the "flossing" dance move, which originated in the game.

Person on insta said it’s from Fortnight? pic.twitter.com/gpPGee0WNf — Sela Shiloni (@selashiloni) July 6, 2018

Season five of the game, released Thursday, is set one day after season four. There's a missile launch to investigate and mysterious rifts appearing over the map. There are, of course, new ways for players to dress up their avatars, more vehicles to ride and new items to hold — all small but beloved elements of the game that have prompted players to drop more than $10 at a time on various purchases.

If players aren’t playing, many are still watching on Twitch, a platform for popular gamers to stream their live gameplay to an audience. The best gamers on Twitch make money from subscriptions, fan donations and sponsorships — all of which can rake in enough money to allow them to quit their full-time jobs.

Rachel "Valkyrae" Hofstetter, 26, is a Fortnite streamer on Twitch and told Business Insider last month that she earned enough money to pay off her mother’s debt.

While the game's popularity has meant big bucks for some, month over month growth has slowed.

According to Van Dreunen, “the importance of season five is for Epic Games to continue to innovate to keep the momentum going and not stop the eight-month honeymoon period.”