I think this is a game that could be really solid with a few tweaks. My more minor issue is the character's physics; they feel pretty slippy-slidey at the moment, and I wish I felt a bit more in control. I also noticed that I got stuck when jumping into the side of platforms; I couldn't tell if this was intentional or not, but it didn't feel natural at any rate.
The bigger issue in my opinion is the fact that I can't see platforms that aren't in my current 'dimension'. Playing through this game, it was pretty much constantly a guessing game on what would happen when I hit the space bar because I had only a vague idea where the platforms were. This was mainly an issue on level 2. This resulted in a fair amount of trial and error where the only way to know what to expect when dimension swapping was to try it and die a few times. If there was some kind of tell as to where platforms are in the other dimension, like a dotted line, I think I would've had a much better time with the game.
All that said, I think the core idea is still workable, and if these problems were fixed, then all the game really needs is some more levels to be a pretty enjoyable experience.