This was an extremely clever take on the theme, and a great concept overall. I liked the backstory, the mechanic idea and the art. I think that the level design ended up being a little frustrating - I felt like Nothing dying should’ve respawned you at Everything rather than at the start, it felt very hard to make progress. And I think starting in a large open space to navigate didn’t lend itself as well to a puzzle game with this mechanic.
I think the reason a lot of puzzle or precision platform games use rooms that are relatively small is to give you quick resets back to the puzzle without reducing the challenge itself, and so that they can put the emphasis on the mechanic (thinking like Portal test chambers for instance). This game is so creative, I think it would be really nice to see a rework of it after the jam potentially exploring some alternative level formats to find the perfect fit for this mechanic.