Wow, I beat it. I died 98 times but I beat it. I absolutely loved this, and I have a lot to say about this game because I loved it so much.
I think the cycles can be a little unforgiving. It seems like the enemy movement is intentionally desynced from the beat, which makes sense at first but results in a lot of waiting around for my gravity change to line up with the enemy's movement (the boss at the end was the toughest instance of this). One potential solution for this is to make the enemies move on a multiple of the beat (i.e player gravity changes every beat, and the enemy moves every 2 beats or 4 beats or 1/2 beat).
Another small frustration I ran into was the fact that there were many rooms where you'd be falling very fast and need to react to oncoming spikes. There was one particularly cruel room where you'd fall upwards into spikes right next to the checkpoint, and you'd have to basically know beforehand where the spikes were so you could fall and move instantly.
Now onto the things I loved: Basically everything else! The first time the beat switched to make the gravity go left/right instead of up/down I had the biggest smile on my face. The music was fantastic and every additional mechanic felt so fresh and fun (I did not expect the shooting mechanic at the end!). I've developed beat-syncing in games before and it's deceptively hard, so you did an excellent job given the constraints. I really appreciated the ability to control the latency whenever the music did get desynced.
In general I had a massive grin on my face the entire time while playing this. There were definitely painful moments of me shouting 'NO!' into my computer as I fell into a spike right next to a checkpoint, but those made my victory even sweeter. I also loved the celeste-style coins that would follow you till you hit safe ground.
Awesome game, this might be one of my favorites of the jam!