A little to easy for my liking. You can just sit on a platform make yourself a coffee shoot some fireballs and go back to the kitchen to make a sandwich.
You should make on your character controls snappier. Currently the character is way too floaty and slow. This might be bearable for aśuch short game, but it will be a dealbraker in an actual game.
Also I am pretty sure that you forgot to deactivate the fireball ability before talking to the rocket boss. I blasted him with fireballs while he was talking smack and he instantly died when the fight began.
Comment below gives good advice. I haven't worked with Godot, but I know that this is an easy fix in Unity.