Best free Mac OSX strategy games

In strategy video games the player has to think and plan every move to successfully progress in the game and win. In most strategy games, the game world is represented from a top-down or isometric perspective in order to help the player to manage armies, construct buildings, etc. Strategy games often involve exploring, manage the economy of an empire, fight tactical battles. Some of the most popular strategy subgenres are: real-time or turn-based strategy, 4x (eXpand, eXplor, eXploid, eXterminate), wargames.