Love the game played it for over 10 hours. Any tips for the final boss? I have collcet every thing exept 2 heart things. 
Wow! I'm so glad you are enjoying it! 10 hours, thats impressive! The final boss is my first boss so it isnt perfectly balanced but it is fair for the most part. Heres some advice:
There are two variations of the bullet hell move, each of them has a safe spot either in the corner or the middle. When you reach the halfway point the corner variation becomes very hard to dodge but you can do it by staying in the middle and continuously dashing left and right to avoid the projectiles.
Basically just spam projectiles and bombs as much as possible. You can also kick off of the laser which lets you get more damage instead of ducking under it. You can also destroy the falling rocks with your sword.
dont stand too close to the boss because the jump attack might hit you on the way up. Also when he does the jump attack its best to jump over the projectiles and get a few hits in before the next attack.
Two sort of advanced things you can do: after kicking off of the boss itself you can hit it with your sword during the flip if you time it correctly for extra damage. You can also cancel your sword cooldown by quickly ducking and unducking which is kind of broken cause it significantly increases your damage output but it's pretty fun.
I hope you beat it! Lmk if you do