As a fan of platforming games, I am really impressed with your work. The game starting with the boss fight and the rewinding ability reminded me for a moment of Braid, but no I was so wrong. After I got the first ability, I saw that it was much more than that. I enjoyed much the game, as the level design is pretty impressive. The graphics are really cool and I think suit the style of the game, but I had some minor bugs, like the player sprite getting stuck in a fixed angle, or the jumping frog thingy animation playing even when on ground.
I enjoyed the mechanics, especially that you can jump back in time, while keeping your abilities (but the hearts tho :( :D ). Although, I must say that the keyboard controls are not the best, as I had trouble shooting and jumping while dashing through enemy attacks or lasers, and eventually using the rewind feature. And I have somehow, after a few unknown keypresses opened some debug list (i think) with all the abilities. Better be careful with that when publishing next time.
A high quality metroidvania with some astonishing twists. Thats what I would call it, even though it is not complete. Good luck with your project, and cant wait to see more in the near future. :D ^_^