Nice game ! I Loved the "destroy gameobject" projectiles of the boss ! A lot of game dev jokes ! There is a clear potential for a cool plateformer / puzzle game with the boucing balls and the momentum jump. Btw powned the boss 1st try by standing in place ahah.
How I would improve upon this though : more juicy feebacks for every action/event of the game (visually and with sounds), more plateform and puzzle levels of course, maybe some hard to get collectibles (like in Celeste, SMB..) exploiting the jump to momentum jump to double momentum jump (shoot while mid air after momentum jump to make a second one, did it some times :p) and finally i'll add some enemies to shoot or to rush on with momentum jump and hidden rooms by clipping through random walls.