First of all, I'd like to say well done, this is a very interesting concept. I've made a list of things I like, as well as some constructive criticism.
Things I liked:
I like the concept. When done correctly, moving the orbs is quite satisfying, and the atmosphere and music are both spot-on. The combat was well done, and final boss's attacks were impeccable, giving the simple, smooth movement a real chance to shine.
Things I didn't really like/suggestions:
I think the game is balancing too many elements. The moving of the orbs feels almost like something from a puzzle game, while the enemies + boss fight feels like a run 'n gun. They're both interesting, but currently they distract from each other. Also, for a game about orbs, we don't actually get to do much with them. If possible, try to make the orbs more relevant to the combat. Maybe make it so that you can use them to attack somehow?
Altogether, a very nice demo, but I'd personally suggest doing a little more polishing on the basic mechanics with the orbs before creating a full game. I look forward to whatever you do with it!
