Nice game! I liked how you had many different kinds of enemies, and I liked the effects for shooting and killing enemies. It all felt really juicy. The simple graphics also really work
Unfortunately I couldn't play this game for very long because the camera moved way too much when you aimed the mouse, and it made me kinda motion sick. Maybe consider toning that down because it makes it really unwieldy to aim and as mentioned before, is kinda sickening to follow the mouse movement
But besides that minor issue, good game well done!