Thank you for your words!
I would have loved music-stage integration too. Before putting the stage together I thought in fact the music could help as a guideline, but I ended up building the whole stage on Wednesday so I had no time to think it through and just put together patterns I had made in the most reasonable way I could.
The first phase of the boss does indeed have unreasonable movement, though I adjusted its HP so it takes around 20-30 seconds to kill it if you focus shot on one of the sides.