Really cool intro! And overall, some quite nice visuals - I especially liked the parallax effect.
It was a bit hard to kill enemies, so I chose to mostly avoid it - which is ok, but a bit strange since it is themed around a weapon. Also, there was some bug with jumping - sometimes I jumped like twice high or so. Or was it a feature? I didn't quite understand.
Overal - nice submission! Could also benefit from some more sound effects and music - the game became silent when the music stopped.