Interesting concept ! The art is quite good and it has the atmosphere of a joyful little game, that's nice ^^ ! I'm not a fan of the control scheme however : the fact that the same finger is in charge of two actions I, somtimes, want to do at the same time (jumping and shooting) is a bit frustrating, and switching weapons with space is not natural for me ^^'. I would have prefered something like "space to jump, left mouse button to fire and right mouse button to switch (or other right-hand buttons, if you don't want to use the mouse)".
But this is a nice prototype nonetheless, that could become better with a bit more polishing ^^ ! Congratulations !