I did search, but didn't see anything about this situation.
Say my LP is 8000, opponent's is 6000.
I use Celestial Transformation to summon Mars. Mars' 0 ATK is halved and at the End Phase it will be destroyed.
I then play Sanctuary on the Sky. Is Mars' ATK now 2000 or does CT's "half attack" effect still apply after Mars' atk changes?