Risk of Rain 2 has sold over 1 million units during its first month on Steam Early Access, according to developer Hopoo Games.
The multiplayer roguelike managed to attract 650,000 players during its first week on shelves, with Hopoo using a novel buy-one-get-one-free promotion to drum up interest in the title.
The offer gifted players who purchased a copy of the $19.99 title within 48 hours of launch an extra copy that could be shared with a friend.
As part of the deal, around 150,000 players earned the chance to bring a pal into the fold, putting the sequel on track to cross 500,000 sales during its first week.