The concept is interesting and looks pretty nice. It has a lot of potential as an arcade game. The good think about its design is that it makes your arm hurts, and it is part of the experience if you put the player in the place of the solely living part of the dead body. The bad thing is that sometimes the arm didn't respond as I was expecting and that was a bit frustrating.
Good adherence to the theme both mechanically and aesthetically. It could be improved by making the arm not just using a sword but forcing it to move the body to another part.
Looks like an original idea with great potential. Maybe allowing the arm moving around could make it more interesting, or having other levels with the breakable ground and that kind of things.
Bug: I found that placing the arm in the right place makes the game easy. Here you can see what I mean: https://streamable.com/08snb