Great game and a pretty cool atmosphere to it too.
I liked the overall gamefeeel, once you get the hang on the controls you can end up warping around quite fast, i also liked the fact that when you get hit with the shard, you get a chance to take it back and not have a one hit death untill you get hit without it, and yet it's still a good fit with the theme of "Only one". The ambient music really set the mood and the pixel art is gorgeous.
I'd tend to agree with what most people already said here, it could be a nice improvement to have a way to recall the shard.
Other than that thats really a cool entry Well done and keep at it :) !