Good audio cues, though the my vital organs one got on my nerves after like the 5th time. I guess that's a skill issue on my part. You can add audio files to a death audio array and then have the audio stream player pick_random to alleviate that.
The first time I died I almost said I was done with the game, but then the game respawned me right where I died. This is the ONLY game I've played in the jam that has a checkpoint system, so well done.
The level design and mechanics are good. The controls are pretty good, though he could feel a bit better to move around. I think perhaps his walk without shift is a bit too slow. Walking is good for aiming but a drag to move around the level due to the speed, and the shift dash is bad for controlling movement and annoying to have to retrigger. So maybe hold shift to run and press caps lock to dash, or something. or just have him speed up if you hold down the movement keys a certain period. I also think clicking once should also shoot one bullet. As initially I was like "why isn't he shooting?" until I read you had to hold it. Enter the Gungeon has a similar setup to yours but feels great to play so you can use that as an example for the movement and controls.
Also, I expected my dvorak keyboard layout to automatically work as this is using Godot, but it didn't. It's a weird thing most people don't use, but something to keep in mind for finished games in the future. Godot will let you map to the physical key rather than the layout key, and i think that's what you normally want for games, and I also think it's the default if you add a new action. Not a deal breaker though just something to watch out for in future titles.
Good job, one of the better jams I've played.