What a gem!
My personal highlight in this are the controls, they are super well made and thought out!
There was only 1 thing i would love to have changed, and thats when you turn around(left or right), that the aiming line is MIRRORED instead of reset to a straight left/right!
You could easily make a more fleshed out, in-depth version of this, with perhaps even multiplayer(!!!) in it, and you'd have me hooked for good!