This is absolutely a really neat idea that I think was executed very well. Movement is smooth and fluid, the controls are tight, and it's really fun. Generally so but it's especially fun to pull off cool moves and learn new techniques, like learning to juggle your sword to move without having to pick it up. This seems like a game with a high skill ceiling, where putting in a lot of time to master the controls would allow you to pull off some crazy stuff.
I think that what's here is super neat but it really left me hungry for more. I'd absolutely purchase and play a full title and I hope you or someone else does more with this gameplay mechanic.
Only gripe is some sorta inconsistent game design with enemy types. I don't really know what to suggest about it, though. It feels backwards with how jumping on enemies usually hurts you but some are safe (and necessary) to jump on. Usually it's the opposite in games. Doing things differently isn't bad but it seems harder to visually convey "you need to jump on this enemy" than it is to convey "you can't jump on this enemy." I thought I had learned a lesson from the blue bug but then died to the very next enemy, a boss, because I thought I could jump on it. Not a huge deal--especially since death isn't very punishing--but it stuck out to me as a tiny flaw.
Anyways, really great game imo. Good job! :)