It was really unconventional and surprising to see a 1v1 boxing game, when there were all these games around trying to focus on constructing time travel stories. Full points for out-of-the-box thinking.
I think the game could use a lot more polish in terms of audio, music and most importantly, some kind of visual indication (apart from the declining health bar, of course) that the player is taking damage. Maybe even as simple as a red flash.
The rewinding mechanism was well implemented and executed, though I was able to beat the opponent without using it, so it felt a bit redundant.
Overall it was a fun game, and the humanoid was nicely modeled considering you did it from scratch.
Praiseworthy effort, and good luck!