Very interesting concept, one of the most creative uses of the theme I've seen so far. I love the style and approach! Clearly the work and skill gone into this is very impressive, and I feel like its something that could be refined into a commercial game for sure.
I understand why you broke things apart on each death to explain more concepts to the player, but having multiple 'unwinnable' battles to start the game felt a bit frustrating. Knowing I have to stand there and get hit until I die to get the cutscene to then actually tackle the fight properly took out some of the fun for me unfortunately. It's a hard thing to balance because having to fail within a game is disheartening, but then if you provide easy enemies the player doesn't get to make use of the mechanic, so perhaps in a larger scale version of the game the mechanic could be confined to boss battles only or something?
Another small suggestion would be to offer a 'reset battle' option from the pause menu, as I got into a bit of a state at one point where I didn't realise occupying the same block as a copy would cause me to take damage from their projectiles, and then my copies were all at the back row so there was nowhere I could go to win the battle unless I purposefully died two more times.
I don't want that to take away from the entry though, as you're clearly very talented and to tackle what you did during the time period is incredibly impressive. If anything it's a testament to your creativity that I could see this being expanded and sold as a full indie game!
Nice work on a great entry :)