Very nice! I really like the progression. I am amazed by how polished this actually is. And I like the art! Although I realize it was probably a Stylistic decision, I found the font a bit difficult to read. Also, the controls (to me) where a bit strange, I would expect the W key to propel the submarine forward, i.e. if I'm turned to the left it would make it go to the left, but that's just me. I got used to it after a while. I really like the progression you did with the "Vampire Survivors"-like upgrades. Good job!