It's a good start. In terms of game play, I felt like the projectiles were too slow and disappeared too soon. As a quick fix, I'd suggest adding the player's horizontal velocity to the initial projectile velocity so that bullet physics feel more natural. (with the current game, if I spam the shoot button while running, I can almost outrun the projectiles). And then also don't remove the projectiles until they're off screen.
Oh, also I was confused with the starting screen... there were three circles and I didn't know what was happening. Nothing I pressed seemed to do anything (and then I think it was Select that finally advanced into the game level)