Hi... When I got my 3DS XL, I made the mistake of having Best Buy put invisibleSHIELD screen protectors on it, before I ever used it. They made the top screen look terrible so I took it off and replaced it with a Hori, but I left the invisibleSHIELD bottom protector on because it worked well. Anyway, screen protector or no screen protector, the top screen of my 3DS XL has always looked weird. Even with the 3D slider at the lowest setting, the colors on screen are a bit muted and strangely colored, and when I move my head or swivel the screen side to side even slightly the image seems to shimmer between dark and light rapidly.
I dealt with it for a while, when messing around with the 3DS interface or playing Fire Emblem: Awakening, but just recently I started playing Pokemon Y, and for the first time ever the shimmer effect doesn't happen, the top screen acts normal! But only in the world map, when walking around towns and such; maybe this is because the 3D slider seems to have no effect in these areas. The shimmering still happens in some cutscenes and always in battles. I'm now thinking I might have a defective screen; hopefully this is under Best Buy's warranty, or Nintendo's.
Any advice with this? I can't seem to find any similar situations online.