While I still haven't had the chance to go hands-on with the game--I would have spent ALL of E3 playing it--the new demo revealed a good amount of new information, systems, and features for the game. These changes may seem minor to casual fans, but dedicated Civ players will likely find the tweaks promising.
Conditions for victory have been tweaked across the board. The Domination victory now only requires ownership of all enemy capitals like in Civlization Revolution. For a Science Victory, players must still send a spacecraft to Alpha Centuari, but it must now be assembled in your capital. Pieces in transport from where they are built are vulnerable to enemies. A Diplomatic Victory is still obtained by vote after the United Nations is found, but now the non-player controlled city-states--new to Civ V--will be voting members. Finally, a Cultural Victory is achieved by completing the Utopia Project, which is unlocked after completing 6 of 10 policy trees, which offer bonuses to different game systems and use culture as currency.
These policies serve to replace many systems not making a formal return from Civilization IV, namely the civics and religion systems. It is possible the espionage will also make a return here, but I was not able to freely browse all of the policies. Policies are broken down into 8 categories representing different ways of governing. Some will be incompatible with others, for example, "Freedom" and "Tyranny." Culture, which is generated by cities, will be used to purchase policies. One early policy, for example, grants a 33% boost in production for Wonders.
On the combat side, units cannot share a hex with other units. Cities have also gained the ability to defend themselves, bringing combat out of cities once and for all. Terrain bonuses will actually mean something in Civ V as small forces will need to exploit terrain to successfully repel (or destroy) a larger force. True ranged units also enter the fray with artillery and archers able to fire upon units from afar. The trade off is that these ranged units are complete rubbish in melee. Once the city comes under siege, however, it defends itself until reduced to zero health points.
Upon capture, the conquering player is granted three options instead of the classic two. First, the victor can simply raze the city. Unlike Civ IV, however, this will take a few turns offering the deposed player a chance to liberate the city. Second, a new governor can be installed, which brings the city into your growing empire. You will gain full control of the city, but it will generate a large amount of unhappiness, stunting growth and production. Finally, players can now install a puppet government. By doing so, less unhappiness will be generated, but the player cannot control the city at all. You will gain gold, culture, and research, but the city will act upon its own best interest. If you're at war and are cranking units out for the war effort, this puppet city could be working on a granary if it needs it for its own development.
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On the infrastructure side of things, Civ V will bring custom maps and scenarios directly into the game with the Mod Repository. Now, content creators will have their work visible within the game and players can install new mods with a single click. This should help get mods out to the community at large without relying on external websites. Since Civilization V uses Steamworks, it will have access to your Steam friends list for game invites and more. On matchmaking, Firaxis is currently looking into whether or not this will be added, but it definitely won't be in by release.
Civilization V will be released on September 21 in the US and on September 24 in Europe for the PC. A Mac version will likely be released at some point, but no timeline has been given.
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