Nicely done! This was solid all-around!
One thing that I did notice right away, it felt very fast-paced, the effects were good, and the controls were good enough. However, having the projectile held in the center of the screen and obstructing the point of view where the eyes naturally want to come to rest in this kind of game was awkward. I would definitely recommend dropping the hands to the corners or the bottom third of the screen to make them and then particle effect less intrusive, I believe the whole thing would feel better.
Other than that, there really isn't much to offer constructive criticism on within a game jam timeframe. You did an excellent job of reusing code, assets, and mechanics to make a boss that felt different enough. I am also sure you know that everything could have used more polish and a little more depth, which is sort of expected within this kind of time constraint. Great submission, keep up the good work!