Hey! Played through the first five or so levels — fun idea!
The concept of controlling the sword and not the character is interesting and has a lot of potential in my opinion. Your prototype has some good variety with different options to use the sword and sword/human dynamic.
The main issue I see here is not enough attention to the feedback — I don't know if my slashes even count, cause when I slice around my enemies they don't die right away. I would suggest adding the health bars to the enemies if their HP is more than DMG of the basic sword attacks, or changing their color when they are hit. Also the flying damage numbers should fit. It can be further improved with some OnHit SFX (even on the prototype stage they can convey some useful info).
I would like some more attention to the difficulty curve, as it can help the player understand the abilities better through predesigned first levels that teach basic mechanic (for example the first level can have only one static enemy and only slash available, and the second is one dynamic enemy within the small box to get used to repel).
And as a UI artist I think the HUD UI deserves some work with hierarchy and visibility. If you have only 2 important stats so far — make them a bit bigger and closer to the focus point of the player. I would suggest not placing them together in the far left corner but rather placing the kill counter on the top center of the screen with some bigger font option. As for the Hero HP — it is hard to understand it in such numeric values. HealthBar on the bottom center of the screen would help, or you can try to place it above the hero, as the player would be focused on what's going on on the actual level as they're playing (mind that the hero's healthbar should differ from those above the enemies, if you choose this approach).
Overall — clean prototype that can become a pretty solid game core. Good work on your journey!