Unreachable panel is very confusing. The area looks like the player is supposed to reach that right now and here, which I have tried and wasted the time. This part was not cool, but however, I definitely like the idea and concept. The most unusual puzzle mechanic I've ever seen!
Indeed, it’s also an issue from doing a demo for a ‘short’ game with such a compact environment, you both have to show that there is more to the game than what is available to the demo and can’t exactly remove parts from the level design (only a single panel was removed to put the end of demo panels instead & to block further progression). Although I guess it could be made clearer that some panels aren’t meant to be for the demo parts, maybe putting a Locked icon instead of the rhombuses on those for the demo could help so players don’t lose time thinking of ways to get to places they can’t reach anyway.