The concept of the game is....... "Used" and the controls are a bit wonky, when shooting it seems like the the (bullet/beam) kinda phases through the monsters.. It could be that that they don't die in one hit but it really doesn't give that feeling, maybe you could give them some sort of "hurt" animation when you hit them or maybe some sorta flash of red or something. plus there should be waves of enemies  instead of just over spawning them, some in-game tutorial would help giving a sense of what to do then just making an info page in the main menu.