Coal mine

Coal mine is the basic mining building. Deep in the dark and dusty caves, your miners dig out this important resource used mainly for researches. Sometimes, these workers come out so filthy that are often mistaken by monsters wondering outside of the village walls.

Requirements

Is required for
 * In order to make this building available, a player must research the 2nd level of Masonry technology.
 * Not defined

Main statistics
Coal is defined as an advanced resource. Its usage is primarly to conduct various researches and used to train units from the Workshop. It is also used for constructing some buildings. If you want to focus on researching, you will have to upgrade the Coal mine as much as you can.

Tips & tricks
 * Coal mine is pretty cheap on the first levels, but its price rises faster than the price of the basic resource buildings such as Lumber camp, Stone quarry and Grain farm. It's up to you if you want to focus on technology or something else, but it's advised to have at least a few levels of Coal mine.

Upgrades and resource gain
You need almost the same amount of lumber and stone to upgrade Coal mine.

Cost per level upgrade
Cost = Base cost x 1.2 (Coal mine level - 1)

(Base cost is 55 lumber, 65 stone and 30 food)

Resource production
Production = Acceleration x 45 x Coal mine level x 1.1 Coal mine level
 * PPH - Production Per Hour
 * PPD - Production Per Day