Absolutely amazing!!! I love the hidden diamond on the first level, I feel a great sense of pride that I got all 6 diamonds, and I would definitely play more of this game in the future! The second to last level with the spikes really got me for a while haha. The only thing I would change is making the effect of the switches more obvious (maybe camera zoom or even playing an accept jingle like in Zelda). It took me a bit to figure out what the switches were actually doing. Very well done indeed!
I'm also curious if you've heard of The Dreadful Whispers by Blackthornprod? There is a similar effect where there are two parallel worlds.