Huge fan of this track from one of my favorite movies, been trying to figure out the intro guitar chords and the variation that takes place of that same riff at around 23 seconds. Trying to learn to play by ear but this one is stumping me, any help at all would be appreciated!

Thanks friends!
From what I can make out, the riff is just simple power chords. The main riff consists of A and B while the variation is G and A.