While the controls, music and soundeffects are good I think (Note this is just my opinion) you should tone down on the glow effect, maybe make the players projectile have a bigger hitbox and I think you really should have some sort of shield mechanic as I had to stand in the projectiles path if I wanted to dmg something.
Also the spider enemies are the first boss but with low health maybe change them up a little? or add a extra attack for the boss?
Cheese strat: if you move to the right so enemies spawn you can move left so the get off screen and kill them without them attacking back.
Jam related feedback:
I dont feel any "rush" to get to the boss and have not noticed the theme of "self destruct" (the theme is optional but you did not say anywhere that you were not using it)
However the most important thing in the Jam is just have fun making the game! all of my text is just suggestions and can be ignored. Im not the best at typing feedback so I really hope this did not come of as rude.