Fortnite, already a pop culture phenomenon, just achieved a business milestone.

The free-to-play title generated the most annual revenue of any game in history, raking in $2.4 billion in 2018, according to estimates from Nielsen’s SuperData.

The firm said Fortnite’s multi-platform release on PC, console and mobile allowed it to reach a massive audience. Publisher Epic Games kept the momentum going by regularly updated the game with new modes, weapons and environments.

Fortnite also revolutionized game monetization with battle pass, a limited-time, in-game purchase that rewards players with digital items they need to complete challenges.

“Games like Dota 2 have sold battle passes in the past, but Fortnite made them a core part of its monetization strategy, with 34% of U.S. Fortnite players buying them regularly,” SuperData notes in its report on the state of the game industry.

Free-to-play games accounted for 80% of all digital game revenue, which reached a massive $87.7 billion in 2018. There continues to be strong demand for “premium” games, especially in North America and Europe, though publishers are moving away from physical discs to digital downloads. SuperData estimates such elaborate console and PC titles brought in $17.9 billion in revenue last year.

SuperData also noted that Asia’s mobile games market continued to grow, despite a regulatory freeze on new game launches in China. Tencent’s Honour of Kings nearly rivaled its popular League of Legends title.

In the North America and Europe, casual games like Pokémon GO contributed to a 13% increase in mobile game revenue.

Here’s a ranking of the top 10 free-to-play titles, by game revenue: