Battle Royale: These massive hits are battling to be the biggest video game in the world

"Fortnite" —as it was originally concieved — is a third-person shooter that's focused on survival gameplay. You, or you and a group of friends, take on hordes of enemies from the tentative safety of a fort you've crafted.

It launched on July 25th, 2017, and is available on Xbox One, PlayStation 4, PC, and Mac.

There's a cartoony art style to "Fortnite," which tonally fits in alongside the game's goofy dialog; there's a playful tone about everything in "Fortnite," which is starkly different from the dreary, dire tone of "PUBG." Moreover, the core of "Fortnite" is very different from "PUBG" — it's essentially a "tower defense" game.

In "Fortnite," like other tower-defense games, you're defending an immobile thing from waves of enemies. You have a period of time before the attack begins, when you're able to set up defenses (turrets, traps, walls, etc.). Once you trigger the battle, you must defend whatever that aforementioned thing is from being attacked. If you survive those waves, you've succeeded.

"We love Battle Royale games like 'PUBG' and thought 'Fortnite' would make a great foundation for our own version," a September 12, 2017 Epic Games blog post announcing the new game mode said.

And so, Epic released "Fortnite: Battle Royale" as a free addition to the game. Better yet, it was free even for those who didn't own the original "Fortnite." Anyone could download it and get to battling.

In retrospect, Epic's blog seems prophetic: "Fortnite: Battle Royale" is outrageously popular, eclipsing the original game its built upon.

Somewhere in the realm of 45 million people have the game across PlayStation 4, PC, Xbox One, and Mac. The iOS version, which is a standalone version of the "Battle Royale" mode, has somewhere in the realm of 11 million downloads according to Sensor Tower data provided to Business Insider.

Initially, "PUBG" parent company Bluehole Studios took issue with "Fortnite: Battle Royale." There are some major differences between the games, but they are foundation ally very similar, in the sense that they place 100 people on an island for a last-man-standing shootout.

In the months following that early dispute, Epic and Bluehole seem to have squashed the beef. "I've tried to combat the perception that we're competitive with other 'Battle Royale' games," Greene said in March. "Its great that the space is expanding. We're happy that more and more people are getting to play games."

On April 2, PUBG Corp. filed a lawsuit in a California court against Chinese game publisher NetEase, over allegations of copyright infringement. The suit, discovered by TorrentFreak, seeks a relatively small amount in financial damages — just $150,000 "per infringed work."

The aim of the suit is to stop NetEase from selling its "Battle Royale" games altogether: "To remove each and every version of the games 'Rules of Survival,' 'Knives Out,' and similarly infringing games, from distribution and to cease developing and supporting those games," the suit says.

It's the strongest move yet from the folks behind "PUBG" to defend their work, and it makes sense. "Knives Out" alone has 25 million downloads, with $50 million in revenue, according to SensorTower data provided to Business Insider. And that doesn't include China.

The question at the heart of the lawsuit is whether it's possible to infringe on a video game copyright. How different does a game have to be from "PUBG" to be considered legally different?

Playing "Knives Out," it's immediately clear that it's very similar to "PUBG" — but it's also clearly not exactly the same game.

In the case of "Rules of Survival," the comparison is a bit more dramatic. Look at this image from the lawsuit document — "Rules of Survival" is on the left, "PUBG" is on the right:

PUBG Corp. is also claiming that NetEase intentionally misled consumers into believing that its games were related to "PUBG."

Most video games take a lot of time to make — years.

The "Call of Duty" game that comes out this holiday will have been in development for several years by the time it's ready to launch. The Activisions and EAs and Ubisofts of the world haven't had enough time yet to create a "Battle Royale" game that could take on the likes of "Fortnite" and "PUBG."

But they're coming.

"While we have yet to see direct competitive modes from our publishers under coverage, we fully expect [Activision, Take-Two Interactive, EA], and virtually everyone else to come up with their take on the 'Battle Royale' genre," Macquarie Capital analysts Benjamin Schachter and Ed Alter wrote in a note this week. They also expect major publishers to build "some version into key known franchises, as well as potentially releasing various other stand-alone titles" in the "Battle Royale" genre.

Indeed, it would be entirely unsurprising to see a few new "Battle Royale" modes or dedicated games show up on stage at this year's big annual video game show, E3, in June.

The battle royale to be the biggest game in the world rages on.