Good idea. At first I didn't read the description and didn't check out all the NPCs so I was just walking around and trying to cheese up the mountain with no sphere... Then I found the moon sphere and went up there without the sun sphere... The platforming seems impossible at times where I couldn't fully make it from one platform to the next and landed a bit below the edge but could "cheese" up onto the platform. Holding space for longer enabled higher jumps which didn't seem to be mentioned anywhere. Instructions could maybe be clearer but that's partially on me. The idea to hint to the spheres with the lights is good, maybe needs to be clearer for people like me 😅
I'm assuming the terrain is so rough is because it uses an 8bit heightmap and not a 16bit one, that could be improved.
Maybe the whole world should be smaller and the platforming to the mountain top be shorter. It takes too much time. When I restarted after reading the description to check all the NPCs and got the sun sphere I didn't want to climb the whole mountain again. I guess we are supposed to throw the light balls into those pyramids guarded by the shooting snowmen.