Quite a nice doom-esque game! Good job on that! The movement is smooth enough, pacing is nice, the graphic is also quite good! Also that regaining health from blood from the fallen enemy is a nice touch.
The thing that baffles me the most is that there are usually enemy remaining when a wave ends, and the second wave just started immediately, kinda defeats the purpose of using waves in the first place. Maybe adding a breather between waves just to claim the play down a bit? Another thing is that the game claims that different blood colour bring different effect, yet we are never told what difference is that. I would be nice to at least inform the player that information within the game.
Anyway, good job!