With everyone talking about "mech" play and the power of tanks, it has made me want to dive back into playing GO. The game is everything a lover of mech gameplay wants, true position strategy with nothing else. To object of the game is the claim, or fence off more sections of the board than your opponent. Both players alternate placing peices, white first, then black. There is only one basic rule, if a peice is surrounded on all sides by the opponents peices, it is removed from the board.
The only way to prevent this from happening is to create two seperate spaces, or "eye" that cannot be captured. Because you opponent can only place one peice, it is impossible to "surround" the entrenched peices. If you look below, the peices in section "C" have two "eyes" and cannot be captured. Any peice placed in the open space will immediately be captured, making the territory blacks.
Because of these rules, GO does not favor aggression, but the staking out of sections of the board. It is often referred to as a negotiation between the two players, who are claiming sections of the board and then engaging in minor skirmishes to stake out tiny claims. The game ends when both players decide there are no "worthy" moves left and they count up their claims. Lost or "captured" peices count against your score, thus punishing a reckless or overly agressive player. Many first time players find their score to be negative due to failed attempts to sections of the board that were already locked down.
The thing with GO is that it can make you better at other strategy games. The concepts of more passive, none agressive play transfers directly over to games like SC2. Building up a solid base of peices and using that to 'project' control to other sections of the map are key features in GO. And like SC2, when you start playing GO, you will be terrible. But, like SC2, you will learn things with every game you play if you are looking for them. So if you want to prepare for HotS and want to way to think outside the box, you might want to try first, truely beautiful, strategy game.