Great game ! Trying to survive was really fun, and the variety of weapons helped me staying interested in the game.
The improvements I think are the most important, would be to add an indicator to tell you how many bullets you have / when you need to reload, and to add some effects when the player is hit (like a screenshake or a flash) to make it more noticeable, becasue sometimes your health can go down without you noticing.
Great submission !