It's a pretty interesting concept, and have a pretty good mechanics.
But you have a myor issue with the cristals, at first i confuse them with light sources, and decorative element, it blend to much with the eviroment, and it's hard to catch what each one do, the indicators in the botton are too subtle, not sure if is the better placement for it, it take me a while notice them., maybe you shold make the bigger and put each one in a corner.
Look for example in NES Game that have a limited color pallete you can tear apart the interactive elements with the background becase the backgrounds generally has mor detail(like in and old cartoon).