Super Smash Bros. Ultimate is already a huge hit in the U.S., with the fighting game selling over 3 million copies in just 11 days since its December 7 debut. This is according to Nintendo and industry-tracking firm The NPD Group.

This makes Ultimate the fastest-selling Switch game in the U.S. yet, along with the fastest-selling installment ever in its series. By comparison, Mario Kart 8 Deluxe is the console’s top seller with 5 million copies sold. That game launched in April 2017.

Like most Nintendo games, Super Smash Bros. Ultimate should have long sales legs. It could still sell millions more during the Switch’s life. It is also performing well in Japan, where it sold 1.2 million in its first three days.

Ultimate should give a boost to Switch console sales. The system has already sold 8.7 million machines in the U.S. in its first 21 months, and that data only goes from its March 2017 launch through November 2018. It doesn’t include any console sales related to the release of Super Smash Bros. Ultimate.

Our review of Super Smash Bros. Ultimate praised the game’s giant roster, extensive single-play mode, and gameplay improvements, but we criticized Ultimate’s lacking online support.