Joystiq had the opportunity to play Civilization IV and has written an article about some of the new features of the latest edition in this classic turn-based strategy gaming series. One of the biggest changes in Civilization IV is the introduction of hexagon tiles, you can now move in two new directions, and Firaxis has shaken up the gameplay with changes like ranged units that can hit enemies that aren't located in a tile next to you, and they've also taken out the ability to stack units, outside cities you won't be able to place more than one unit per tile.
The game received a big graphics update, there will be a lot of eye candy in the environment, and another big change is the introduction of full-motion video of the other leaders, it will be very important to watch the body language of the other leaders to see how they feel about you. Additionally, the game also introduces city states, a new class that doesn't expand beyond their own borders.
If your computer is powerful enough, you'll really see the graphical jump: waves roll lazily across the ocean; horses stomp on the ground and eat grass; military units adjust their gear. It's a living world with new environment squares hexes that have different terrain depending on which continent you're viewing. Think: Wide sweeping plains, majestic, snow-capped mountains, dense forests, lakes full of slowly oscillating water, and more. This is why your graphics processor and CPU are going to need a real head of steam.