First of all, this is not a review for Pro Keys.
Second, this song should not be heart-tiered.
The majority of this song is a bunch of key chords that are often played consistently, and they're all pretty easy for the most part.
The other progression that appears quite often in the song is a very fun keys pattern where you have a bunch of green notes that can easily be played with your left hand and a bunch of other notes that jump back and forth repeatedly with your right hand which seems tricky at first but is actually quite simple and easy to play.
Overall, this song is not as hard as it seems, and its a hell of alot of fun. Unlike most keys songs, this song doesn't have alot of empty space, so you're always playing. I originally gave this a 5/5, but on second thought, I shouldn't be grading this in comparison to other keys charts. I'm giving this a 4/5 because the crazy progression is alot of fun, but the rest of it is nothing but some consistent 2-note keys chords.