Very cool, disorienting in a good way. I may come back and try to get them all I think I got to 11. I have a few ideas for you.
(1) As others have said, a player model would really complete the immersion.
(2) It would be really fun and even more disorienting if you added color suddenly. You get so used to the stark black/white that if the scene changed suddenly to some different color pallet (maybe when you pick up each orb, but only for an instant) it may be really satisfying and shocking. That also could give some rewarding feedback when succeeding. You could also use different colors to cast shadows from a different source. I don't mean that you should add color in a way that would totally change your art style, just shift the white/black and use it somehow as a mechanic.
(3) I would prefer if each test was setup in the portal style, i.e. each setup/test is self contained and you are ushered off to the next - that way you are never left wandering aimlessly.
(4) The general mechanic is fun but I'm not sure how much farther you could take it without some additional creativity - though I was surprised by how you used it as is, so maybe their is a higher ceiling than I am assuming.
cool game!