Animal Crossing made the leap to mobile last week, and it’s proving to be another smash hit for Nintendo.

Pocket Camp attracted 15 million downloads across Android and iOS during its first six days of availability, according to the latest estimates. That’s more than double the number of downloads achieved by Fire Emblem Heroes over the same time.

Nintendo’s most popular franchises always sell well — regardless of platform. It’s no surprise, then, that Animal Crossing’s first foray into mobile has been successful so far, with more than 15 million downloads during its first six days of availability, according to Sensor Tower.

Pocket Camp is already popular

In comparison, Fire Emblem Heroes reached 7 million downloads during its first six days. Super Mario Run remains Nintendo’s fastest-growing mobile game, however, with a whopping 32 million downloads in the six days following its launch.

More downloads doesn’t necessarily mean more revenue, however. Despite the incredible rise of Super Mario Run, the game has made Nintendo fewer dollars than Fire Emblem Heroes.

That’s because Fire Emblem Heroes employs a more traditional — and more popular — free-to-play system. You can enjoy the full game as much as you like, and only have to pay to get ahead if you choose to.

Super Mario Run, in contrast, asks you for $10 to unlock the full game after beating the first few levels.

Animal Crossing is free-to-play

Animal Crossing: Pocket Camp follows in Fire Emblem’s footsteps. You get to play the full game for free, and you only have to cough up cash for “Leaf Tickets” if you want to progress at a faster pace.

This helps ensure fans play for longer. In turn, that means they enjoy the game more than they would if they were blocked from playing after a short period, and they’re more likely to encourage friends to join in, too.

Pocket Camp will only grow in popularity in the coming weeks and months, then. It could well become even bigger than Super Mario Run in time.