Wading through a literal sea of bullets is great, but there's a lot of visual things here I do not like. The vignettes or shadows on the screen can make it hard to pick out stuff, and there's so many particle effects and everything on screen that it can be hard to also figure out where to shoot or dodge.
The low health red flash is also not something I'm a fan of. I kept thinking I was taking damage when I wasn't. Feel like just having the health bar flash red would be enough. I think I enjoyed this most when I was fighting the worm more than anything.
Anyway, add a train.