Nice job for a first game! It was fun and chaotic! I think the UI like the Wave numbers were pretty hard to read, so it would be good to reduce the glow. Also, the rewind mechanic is a bit useless since there's a high chance you will rewind into a bunch of bullets.
Speaking of bullets, I think having different bullets from the enemies would be a good touch, since you would have more visual feedback for shooting. Also, some SFX with shooting could be cool! Some of the audio was a bit glitchy though, and made static sounds when shooting, getting hurt, etc.
I also think that changing the player's movement speed while shooting could be cool. For example, the speed of the player could be reduced while shooting, or increased when not shooting.
Other than that, this game was nice! I liked how it became a bullet hell after just a few waves!