First of all, really nice game, (btw, i like portal, so it was expected...). I really like the puzzles, the music and the graphics.
If you're open to some feedback, here's what i'd change:
-add the ability to restart the level, so you don't have to wait for the time to kill you
-add a bubble or some indication above the player or an intractable when you can interact with it
-add the ability for the player to end the time rewind earlier
-sometimes, when you die while moving the sprite will keep sliding
-reduce the "hitbox" of the air-sucking holes so that it is confined to the tile instead of the particles
-sometimes the time you have to ponder your next move and execute it seems a bit too short, and it can get frustrating
I'm currently stuck to first level with 3 boxes because some nasty blackouts stopped me, but i'll update this once i finish the game