There are 12 maps in the game which can be unlocked and bought for use in free-play mode. There are 4 of each type of map (the types being Mars, coast/island and forest/grassland). However, there is no "random map" function, as in many other war-based strategy games. There are also a number of maps of all types which do not need to be unlocked at the start of the game. Each map features a different arrangement of 4 types of terrain: grass, dirt/rock, water/acid, and cliff. Each map also contains trees on certain parts of the grass. Mine seams are located in certain positions on the dirt. Buildings can only be built on grass, except for mines, which must be built on dirt-based mine seams, docks which must be built on dirt/water boundaries (the coast), and bridges which are built between bridge slots across water. Water is impassable to all units, except for transports and some specials. Cliffs are impassable to all units. Some water-based specials can't pass over dirt and grass either.