This is a really polished game! The first boss being a mech driven by a top made me laugh a lot. You've got great music, good juice, the intro narrative is really fun, boss designs are all different and cool, and I really like the customization!
One piece of feedback I have is that there is only one shooting sound and it gets really repetitive. When you have an action that repeats incredibly often, I'd aim to have two or three sound effects for it. But even if you only have one a great trick is adjusting the pitch by a random amount when it is played. I like to start with a range range of 0.95 - 1.05 the sound effects pitch and adjust from there. Just that small variance even on a single sound effect makes it so the effect doesn't get repetitive to the players ear.
Awesome job!