Good game.
I like the idea that you need to pick your bullet up and it spawnes in different place every time. From the gameplay point of view you need to plan your road to bullet every time after shot. I have some suggestions how you can improve your gameplay: I would add diagonal movement when you pressing two buttons, like up and right for example. Also, in the chests/boxes you can add different type of bullet, like bullet which shot multiple bullets at the same time in different sides.