Interesting idea, poor execution. I like the idea that the player is constantly changing Eras in time, and the time shift not only is cosmetic, but it also changes the enemy types that have different functions. That's pretty cool. That being said, taking a hit is pretty punishing resetting you to the start of the level (Believe me we are one to talk with our game being similar as well in that regard) 

Animations are a bit fast and could have used at least another frame to really sell it. Most Nes games had at least 3 frames to work with and the ones that only used 2 did it in a way where the timing made it have weight and the brain could fill in the rest. Try lowering the playback speed in the animator and spreading the frames farther a part just a hair. instead of 60 fps on 1s, try 24 fps on 2s, even with 2 frames, it still can come out pretty clean.

That being said, as a Solo dev who did all the art and programing I will give you cootos for it. I see the vision just needed a bit more time to get it working properly.