Ok, I'm going to be a bit harsh here, but i hope it helps you improve. Here's my honest opinion.
I like the minimalist style you went for, and the beginning is very intriguing, and i got my hopes up when i got told the main mechanic. The problem is that i never used it. You don't really need it during your game, and i think a clever way to use it would have been to do something like you did in the final level, but more often, maybe rhythmically. And the gameplay, in general, it's pretty bland, you only need to press to buttons for the most part.
Finally, it happened to me that standing too close to the edge of the arena killed me, i don't know if it is intentional.
I hope you don't take this the wrong way: the premise was good, but i didn't really enjoy the execution, but you can always improve from negative feedback