Any hints for how to deal with the shadow side of the key area? I believe I tried to get to every part in the shadow area but I couldn't get to the key
It sounds like you are in the maze with all the lanterns?
Without fully giving it away, you need to use the puddle (the orange thing the player jumps/slides over) that's near the center of the maze. You'll probably have to bump around a bit in some of the shaded areas, but otherwise that central puddle will lead you to the key. Hope this helps!