I'll start off by saying that the "reveal" of the two parts with the glasses was really cool. Fantastic job with the lead-up and reveal. I liked how you taught the basic mechanics without the double screens and only then introduced the core mechanic. It created a really nice learning curve.
Like some others here, I had to restart that first level with the glasses enough times that it became tedious. In my opinion, a shorter level would have been better there, introducing the split concept but not making the solving of it take too long; that way, people can get used to the controls and how the double-screen situation works before you start in earnest with challenging them.
Also, some feedback on why you died might be helpful? E.g. it was not obvious to me that both parts have to enter the stairs at the same time or you die.
Overall, a really polished and clever game. Well done!