Fog of war

"Fog of war is the technique of hiding unexplored regions of a terrain from the player by showing them as featureless, usually black or clouds. This technique hides regions or some aspects of the terrain, even if previously explored, from a player, if he has no units in the region to see what is going on there. This is used to prevent the player from observing enemy troop movements unless he has units nearby to see them."

- Adams, Ernest (2014).

Types
Initial fog takes place under the world's surface. In Craft the World the fog of war has two stages: the full black and the translucent.

Full black
The full black fog is a initial 100% black layer that only exists on unrevealed areas below the world surface line, i.e. on all earth and lava layers and the sea, except the top surface and areas touched by directly by the sun light (e.g. when there are random generated holes on the first earth layer).

The sun light can illuminate (and reveal) five blocks deep from the surface.

Translucent
The translucent fog is a dark cloud or filter with a intensity variation that occurs on areas:
 * already uncovered by a dwarf approach or the use of the magic light spell; and
 * that do not have any source of light nearby (e.g.: a dwarf, a torch, the mouse cursor, the sun light, etc.).

Consequently, this fog will usually take place on underground areas or over the world surface during the night.

This type of fog becomes even more intense (almost 100% black) in the deep underground at night time.

The cave spirit will only spawn on areas with this fog.

Zooming out for the icons to appear, will help players to spot enemies and minerals. Some minerals like mithril and crystals will sparkle even in a very intense fog.

Game modes
The fog of war will function slightly different depending on the game mode chosen. The default way has been described above and happens in all singleplayer games. The possible differences are listed below.

Coop. Multiplayer
In cooperative multiplayer games, either in biomes or in worlds (with the DLC Dig with Friends), all players will share the same vision. If a player explores an area, that area will be revealed to all players.

PvP Multiplayer
In PvP battles (always in biomes), everywhere over the surface is visible for both players, but the initial fog can only be removed by each player. All the underground activities of the opponent will be hidden, except the location of the opponent's dwarfs, spoted in the mini-map with dots.

Exploring
Exploring the unknown areas can be done with:
 * a dwarf or
 * the magic light spell.

Once an area has been revealed, it won't ever display the full black fog again.

Limitations
Unlike other strategy games, where the player can send units to scout an area by ordering them to move into the fog, there is no such option in Craft the World, except direct controling a dwarf, which in multiplayer games in worlds cost mana.

If the player tries to give an order to be done in a unrevealed area, the dwarf will say:

I can't get through

If not using the direct control, exploring the terrain with dwarfs can only be done by giving them orders on the borders of the revealed area, which is a slow process.

The magic light is by far the most efficient way to explore the world, but it costs one mana and can not be used on top of an area with initial fog. If the player tries to use it, a pop-up message will read:
 * Too far from the explored area.