This game is a pretty solid all around game. The economy is interesting without being overly complex, the units are interesting and customizable, and factions distinguishable. The only issues that I have with the game is that naval combat is lacking and that the game really needs mod support on GOG.
Solves problems of the other 4x. - The turns are efficient - the economic controls and research trees are complex enough to need solutions, but do not distract form the maneuver or diplomacy of the game Has some rough edges. - Could do a better job telling you what the requirements for a military unit are. - One non-fatal error that appears once per game.