Earth :

The planet in this game called Earth is ver similar to our Earth, but the shape and placement of the islands and continents is very different.

Earth has an Undersea Zone - a "Deep Ocean" realm for covert Submarine operations. The modern submarine (but not U-Boats) can travel between Sea Surface and the Deep Ocean, submerging and surfacing at will, provided that the Sub is not in shallow water over the continental shelf. Subs can thus escape attack from surface naval units or air units.

Subs can also carry Missiles so as to lie in wait in the deep ocean trenches waiting to surface to attack enemy targets at an opportune time. Note that unlike the modern sub, U-Boats can only skim under the surface of the sea, they cannot 'dive' into the deep ocean.

Barren World :

Food is scarce in the Barren World. However it is very resource rich. To build cities successfully here you will need to build your cities on on Bare Rock tiles, near Sludge Mites and Spore Clumps. Set up food trade routes from your Earth base cities. Irrigate any surrounding bare rock.

Ancient World :

Internal combustion engines do not work in the Ancient World. You will be forced to rely on less powerful, slower units and employ different tactics to those that are effective on our Earth.