The core is there, and so is the vision, as others have said - having the lifesteal mechanic is pretty neat too! There's definitely some polish that it needs, and some extra features/enemy types to mix things up'd go a long way, as well as maybe some music to tie it all together.
The base gameplay feels a lil weird, with the camera sway and such, so it takes a bit of getting used to - mechanically though, this works fairly well, but it's in desperate need of some polish and TLC to bring it up to scratch.
Not bad for something made in just four days though, a solid start for sure! The bones are there - it just needs teeth now.