OK to add up with the tutorial.
i will discuss the complexity in AA.
I claim that,
AA can also increase your number of colors
because in AA you must follow the rules and that is
by adapting the color of the background
in HalfDemon's example he uses only white background
but what if the background has to be different colors?
this what happens

so AA clearly, doesnt serve its purpose, and ofcourse you wont do this
with your pixelart.
in that case you have to increase the colors
and adapt the color of the background from
the object's (circle) base color (which is black)
to the backgorund's color.. you create 3 levels
of shade from those 2 colors.
and this is the result.

that is one complexity in AA that we all have to know
when using the AAing technique to our pixelarts.