One day, while playing Minecraft, a player ran at full speed up to a tree and dug into the ground. There, they found a mysterious note. It said:
I am a thing.
If you do something to me,
and then do the opposite of that thing to me,
You may think you end up with me again, but...
You will end up with the opposite of me.
What is this riddle referring to?
Hint:
Minecraft has trees made out of cubes.