I completely agree with Kamil about the camera. The arrows and exclamation marks are helpful, but it's still hard to shoot enemies and dodge projectiles from off screen. I also think there should be more invulnerability frames after being hit, since the projectiles come in groups of 3 and you can easily lose all of your lives at once if you mess up just a little, especially once there are two monsters at once attacking from opposite sides.
I loved that tiny intro/tutorial! It says a lot with a little, and shows you exactly what each move is for in a cute little way. I tried implementing something vaguely similar in my game (the button used to start the game also causes the player to attack, so they learn the controls the second they begin the game.) I love when games do this sort of thing, and it made for a much nicer presentation than many of the other jam games which didn't have time to add that sort of thing.
Great submission!