Sid Meier's Civilization IV: Beyond the Sword [PC]

Making an expansion pack is easy. Cobble together some new units, a few maps, maybe a new campaign, and you've got something to put on shelves while a developer works on their next real project. Making a great expansion pack, though, that's hard. A great expansion pack needs more than just bullet points on the back of the box. It needs to revisit the underpinnings of a game -- explore what makes it tick and then adjust it to make the experience richer without losing what made the game great in the first place. That's a pretty high bar, one that most developers never even try for. Fortunately, Firaxis isn't most developers and Beyond the Sword isn't most expansion packs. It's an amazing addition to an already-brilliant game.

The heart of Beyond the Sword's brilliance lies in three new mechanics. The first is a massive re-working of espionage to make it more integral to the experience. Religion gets a good workover with the new Apostolic Palace and the late game race to the finish line is spiced up by the addition of Corporations. Corporations are best described as a latter-day replacement for religion without all that monkeying-about-with-God stuff. The impact of each of these changes is profound and will throw a wrench into many of the tried-and-true strategies of die-hard Civ players.

One of the biggest -- and doubtlessly most controversial -- additions to the game is the change to Espionage. Spying is now a much more integrated component of the game as espionage itself and agent units now become available after the discovery of the alphabet. More than that, espionage has now become a line item in allocating a civilization's production output -- part of the player's fundamental "guns and butter" decision-making between putting production to work creating wealth, research or culture. The "espionage points" that are produced can be used to empower spy units to perform a variety of functions against other civilization. Spies can poison the wells of an enemy city, for example, steal technology or money, switch a city's religion and even foment unrest. Espionage points also generate passive effects that allow a player to peek into enemy cities and determine what enemy civilizations are building and researching.