Thanks for your feedback! though I'd like to make some points clear:
First off, yes, i did take a lot of inspiration from JS&B, i intended for it to mostly be visual design choices, and not much related to gameplay (the idea of syncing the gameplay with music is not just a JS&B thing), but because the project was too ambitious i had to cut corners a bit before the deadline to get the core features done first, and i did leave behind some features that would make the game more unique (some of which include making the player's bullets and the bosses' collide, different kinds of boss obstacles, etc.) in order to submit a game that was at least working as intended.
Speaking of working as intended, dashing isn't supposed to make you invincible to bosses' bullets, i felt like JS&B needed that because you couldn't shoot the bullets and destroy them, and yes in this demo you couldn't too (reasons explained above), but i still didn't add invincibility because the boss lacked diversity and difficulty in his shots, so i thought it wasn't necessary.
As for an extended version, i'm not sure how many people want a better more refined and polished extended experience, and i don't want to work on the game if no one is going to play it, so there is a possibility of making an extended version, but as of writing this i'm not sure.
Thanks again for your feedback, and i hope you enjoyed my game, peace.