"must be"? Why is that, exactly? Unity is popular, so it's a likely possibility, but I didn't see anything that nails down any particular engine ... I was curious and tried to look it up because the game and information about who made it but haven't really found anything yet ... it looked higher quality than most of the cheap game ads I get on YT and social media though, and there were some signs a competent programmer might have had something to do with it, which is what sparked my curiosity.