Vision

Vision describes what a unit can and cannot see within a circular area from its current location and state. Places a unit cannot see are filled with the Fog of War, a dark mist that hides enemy units inside of it. Allied units cannot be hidden by the fog of war. Invisible units cannot be seen even when outside of the Fog of War, unless they are revealed by a source of True Sight. Trees and higher elevation block a unit's vision if it has ground vision. Flying vision is unobstructed by trees and elevation.