When there's a boss fight but the limitation says everything dies in one hit. Lol, that was really funny how the music was so tense but then the boss dies in one hit. I love the game art. I think it's nice and simple. Would've been a lot nicer if everything is just made of pixel art. The bullet and the death particle effect are kinds of messing up the whole pixel art vibe.
For the controls, you mapped it really weirdly. I think you should just use 'W' for jumping, then map another key like 'J' or a left mouse click for shooting. Sometimes you really just gotta think about common map inputs like WASD is commonly used for moving around and stuff. People are used to those inputs and when you change that balance, it kinda messes up with their mind, sorta. Like when I was playing, I think 'W' was for jumping even though the game instructed me that it's supposed to be for shooting. Anyways, that's just my piece of advice. Overall, you have a good game at hand. Well done finishing a game!