I absolutely loved it, I like where it is going! The weapons are nicely balanced and the bosses don't feel like pushovers. I love obliterating bosses but the damage compared to the boss health is a very good mix right now!
I couldn't exactly find where the heart weapon was, although this was the same save as used for the older demo so I don't know if that has caused any issues.
I do have a couple points of feedback. When you are at the height of your double jump, instead of floating for a very short second and then accelerating downwards like a normal jump, it feels like you hit a ceiling and immediately start going downwards. It feels different to the normal jump that you get accustomed to, so it might be difficult to maneuver when double jump is needed.
My only other feedback is damage numbers when hitting an enemy. My apologies if this is already planned to be implemented, but damage numbers makes hitting enemies feel more reactive and can make figuring out what weapon to use a lot easier. It can also show their defense values, which is a really nice stat to have.
Overall, this demo is very good and playing it was a joy. I love how you are revamping the previous bosses, it makes them so much more engaging and all the textures fit your aesthetic very well. Keep it up!!!!!!!!!!