winding or circling around a center and gradually getting closer to or farther away from it:
spiral
a solid shape with 6 square faces:
cube
the scenery or ground behind something:
background
visual; relating to vision:
optical
to examine in order to discover likenesses or differences:
compare
difficult to understand, or explain:
complicated
a misleading image presented to the eye:
illusion
something that plays tricks on your vision:
optical illusion
the part of a scene or picture that is nearest to and in front of the viewer:
foreground
not complicated:
simple