The unlikely success story of “Fortnite” keeps getting more impressive. The popular, free-for-all multiplayer video game reportedly makes an average of $2 million per day on Apple’s iOS platform alone, according to mobile data company Sensor Tower.

“Fortnite” apparently generated a record high of $3 million in a single day on July 13. The mobile version of the game has convinced players to spend more than $150 million it since it launched in the middle of March.

The last thing to consider is that “Fortnite” is not yet available on Android devices; its revenue could potentially soar even higher when that happens, since Android’s market share is much larger than iOS.

GettyImages-972637488 'Fortnite' makes $2 million per day on mobile. People crowd the display area for the survival game Fortnite at the 24th Electronic Expo, or E3 2018, in Los Angeles, California on on June 12, 2018, where hardware manufacturers, software developers and the video game industry present their new games. Photo: Frederic J. Brown/AFP/Getty Images

The incredible amount of money generated each day by “Fortnite” is made even more difficult to believe when considering that developer Epic Games does not charge players a penny to play the game. The only thing Epic charges money for are completely optional cosmetic items like costumes and a “battle pass” every couple of months.

The battle pass costs around $10 or less, if the player has accrued enough in-game currency by playing the game. It gives buyers access to an unlockable progression of costumes, stickers, dances and more. It lasts until the next in-game “season” starts, at which point the slate is wiped clean and a new battle pass is available with new items to unlock.

Last week, market research firm Superdata found that “Fortnite” had made $1 billion just from sales of the aforementioned cosmetic items. Tuesday actually marked the game’s first birthday.

The success of “Fortnite” comes from a few different factors. It can be played with no limits for free and is available on PlayStation 4, Xbox One, PC, Nintendo Switch and iOS. In other words, everyone except for Android owners can access it without having to pay any money and play as often as they want.

It is also noticeably more family-friendly than its main competition, a game called “PlayerUnknown’s Battlegrounds” that launched several months prior to “Fortnite.” That game remains popular, but even its free-to-play mobile variation does not make nearly as much money as “Fortnite.” “Battlegrounds” has a more realistic, militaristic visual style than “Fortnite,” which sports a cartoonish art style and notably lacks blood of any kind.