Fog of war

Fog of war (sometimes called fog or FOW for short) is a common element in Civilization and related games. It refers to an opaque shroud that hides all unexplored areas of the map from view.
Fog of war can be cleared by sending a unit into an area, which will reveal everything in the unit's sight radius (provided it has an unobstructed line of sight to those tiles). Without a unit around to maintain visibility over the area, however, fog of war will be replaced by a shroud that leaves terrain visible, but hides the movement of other civilizations' units and barbarians from view.
In Civilization IV and Civilization V, researching Satellites will clear the entire map of fog of war. In Civilization VI, completing the Launch Earth Satellite project will achieve a similar result. In the Civilization Revolution games, the first civilization to research Space Flight will have their map cleared of fog of war.
Category:Game concepts