It’s a neat idea to use your dead bodies to get yourself across the spikes. 

While the rewind animation looks cool, it is WAY too slow, usually taking around 10-20 seconds before I’m allowed to do anything again. It would have been better if the animation was locked to only run up to 1 second, and speeds up to meet up with that time requirement.

There were a few times where I got softlocked because my character respawned right on top of a dead body, which meant I had to restart my entire progress. Perhaps there could be an area around the spawn where dead bodies disintegrate to prevent this from happening. There should also be an option to restart the level if the player is unsatisfied with how their dead body layout is. 

I seem to respawn when I click off the window and click back on for some reason, I'm not too sure why this happens.

For the beginning of the game, I'm guessing you were trying to let the player figure out themselves how to play by making them die in the spiked area, and then have them realize they can use their bodies to get across. This actually is a great method of level design by making the players feel smart that they figured out the mechanics themselves without being told how to do so.

The one thing the beginning of the game could have needed was the locations of the control inputs. I have around 100 keys on my keyboard, and if I were a newbie who never played a PC game before then I would have no idea how to control my game. A picture of the WSAD labeled “movement” and spacebar labeled “jump” would be enough to show how to control the game.