Decent start. The gun fires WAY too slow and the length of time needed to begin gun charging is very very long. Your respawn point at the beginning of the level simply drops you off the cliff. When that happened to me I thought the game glitched out (which, I guess, it technically did).
Otherwise mechanics were good. Level maybe needed more of a reason for the jetpack. Maybe a few platforms that the player cannot reach via (wall)jumping.