Your controls and camera design are excellent! The dash is so satisfying to use. I really like the visual contrast between the two environments as well.
Including the Assist Mode was much appreciated, I'd often use it to quickly return to where I died before continuing. There's some great atmosphere in your game world, and the title screen is very effective at setting the stage.
It would probably help to give enemy bullets a darker outline, or to increase their size: they can be a bit difficult to see, especially when moving at a quick pace. You may also want to start the respawn transition a little earlier, its spiral cutout nature means that you'll still be able to see what killed you while the screen is blacking out. It's just a little long for how often deaths occur.
I really liked playing this, thanks for sharing it!