Wow! The development of each section is great and it loops perfectly. Regarding theme imo this sounds like a level more than a boss because it has quite a slow pace and has a lot of dynamics and doesn't sound too threatening, I would've liked more dissonance like when the melody does D C# A C G# B in staccato.
The little details everywhere are a nice touch as well, those initial two snares(?) and the Bb arpeggio 'blip' set the stage for the rest of the piece and it delivers!