Sid Meier's Civilization IV free Mac Game

Civilization IV follows some of the 4X model of turn-based strategy games, a genre in which players control an empire and "explore, expand, exploit, and exterminate", by having the player attempt to lead a modest group of peoples from a base with initially scarce resources into a successful empire or civilization. The condition for winning the game is accomplished through one of the five ways: militarily defeating all other civilizations in the game world, controlling over two-thirds of the game world's land and population, building the first spaceship in the Space Age and sending it to Alpha Centauri, having the most dominant Culture ratings over other civilizations, or becoming "World Leader" through the United Nations votes. Additionally, there are multiple game scores for each civilization throughout the game based on the actions of each civilization and a number of different factors, allowing for a win condition based on the total of these points if the game timer runs out. The game can be played in multiple modes: as a single player facing against one or more computer-controlled opponents, in hot seat mode, or through online multiplayer games.

As with other turn-based strategy video games, the player can customize the look and feel of their game world as well as the difficulty of any game AI players before the game starts. Each map space has a terrain type, such as plains, tundra, or desert, that affects the available resources players can extract from their environments and the movements of certain units through that terrain. The player is then given a total of 18 different civilizations to choose from, each with their own pros and cons, plus a leader avatar, an initial set of civilization technology, and any units unique to that civilization. When the game starts, however, it chooses random locations to place across a predefined square grid map. Like other strategy games, Civilization IV has a fog of war feature, in which unexplored territory remains darkened and territories without any units stationed on its designated square is shaded with darker colors.

Units and combat

Most units that the player can generate and use are military units, with certain attributes such as combat strength and movement rate particular to each military type. Each unit can gain experience through combat, which later translates into promotions that the player can use to assign military units new bonuses. Initially, most combat takes place on land, but further advancements in the game's technology tree can allow the player to build ships and planes with which to fight battles on sea and in the air. Any number of units can be stacked onto a single space and move as a group if so assigned, but the overall combat phase is resolved by one-on-one unit battles.

Combat is initiated when moving military units are moved onto the square occupied by an opposing force's military units and cities, and combat is then resolved with calculating statistics of each unit combined with some random chance. Defeated units are removed from the game (apart from workers and settlers, which are captured by the attacking force), and any attacking units that are able to defeat the last defending military unit on a space will move to occupy that space. If the space is occupied by a city the player may choose to occupy and capture the city as their own or raze it. Other than combat, military units can also be assigned to fortify a specific space, perform sentry duties, destroy enemy city improvements, or explore the game world.

Non-military units include settlers who are used to found cities, workers who are used to improve space and gather resources, spies who can perform counterintelligence and espionage, and religious missionaries who can be sent to convert different civilizations and cities. Also, with the Beyond the Sword expansion, new units are added such as executives, who can spread corporations to new cities. Throughout the game, players may also generate a special unit called a "Great Person". These are named after historical figures and can be used for one-time advantage boosts in various ways; examples include Great Engineers who increase overall production levels and Great Scientists who improve technology. Assigning inhabitants of cities to work as 'specialists' (scientists, engineers, artists, spies, merchants or priests), building certain wonders or discovering certain technologies can improve the rate at which Great People are generated. Great Generals are generated when a player's forces achieve a certain number of victories, and can be used either to give a small amount of extra experience to all units trained in a city, or a very high level of experience to one unit. However, like other units, Great People of all kinds can be attacked and killed before the players can use them.