Very cute and easy to get into. Although it was lacking some things, the experience felt polished.
You don't really need a button to discard the guns... just discard them if the player pick another gun using the E.
And definitely make the bigger gun deal more damage... they felt unbalanced.
Be careful with the volume of sounds that repeat too much... Like firing bullets... Try to keep them a little lower so they don't get annoying after a while...
The only thing really missing was a nice boss fight to finish the experience with a golden key.