As the other user noted, this is THE minigame, card or otherwise I compare RPG minigames too. It's not too complicated, never requiring more thought than a single round usually. But it's not simple either. It can last for minutes at a time, but not more than ten, and yet, in those minutes, you'll be watching your numbers, and trying to guess your opponent's next move.
This one, in particular, works wonders because it's complex enough to have several victory conditions. Tower to a certain height, resource to a certain reserve, or even just obliterating your enemy's tower. These are all natural parts of the game, and each color, corresponding to a certain resource, leans towards one of the three victory conditions, letting you know at a glance your general options.
I never played the multiplayer, and I'm not sure I'd be good at it, given that one troll town in VIII(at least I think that was it) kept kicking my butt because it started you with a five HP tower, and the computer kept getting damage cards to end me before I got a second turn...that said, it made the victory all the sweeter when I smashed his back.