Ok, so here are my thought:
It's looks really cool, extremely polished, and the music fits really well, with the rewind and all. And most importantly, it's really fun!
But I think you should explain a bit more at the start. I... well, I didn't know you could move with the mouse and kept trying to move with [wasd] and the arrow keys. Just add a small screen where it says you move with the mouse, or even just explain the controls in the itch page, since people are gonna play it in the browser and have the itch page close by.
I also think that the guns are a bit overpowered and don't fit the game. When you use the gun you don't have to strategise at all about where you are going. You just move in a line, then rewind, and the screen is immediately cleared. Having pickups is really fun though, so maybe, if you have time, I think you should put something else instead.
And one last thing - when I first opened it there was a black window. I waited a bit but nothing happened. Only after a couple refreshes did it work. I don't know why that could happen, but maybe look into it? I think that it might have turned me away from the game if I was just grading a couple games.