Game WQ : UFO:Enemy Unknown

The game takes place within two main views: the Geoscape and the Battlescape. Gameplay begins on January 1, 1999, with the player choosing a location for their first base on the Geoscape screen: a global view representation of Earth as seen from space (displaying X-COM bases and aircraft, detected UFOs, alien bases, and sites of alien activity). The player can view the X-COM bases, make changes to them, equip fighter aircraft, order supplies and personnel (soldiers, scientists and engineers), direct research efforts, schedule manufacturing of advanced equipment, sell alien artifacts to raise money, and deploy X-COM aircraft to either patrol designated locations, intercept UFOs, or send X-COM ground troops to a mission using transport aircraft.
Funding is provided by the sixteen founding nations of X-COM. At the end of each month, a funding report is provided, where nations can choose to increase or decrease their level of funding based on their perceived progress of the X-COM project. Any of these nations may quit, if the nation's government has been infiltrated by the invaders. Through reverse engineering of recovered alien artifacts, X-COM is able to develop better weapons, armour and vehicles to combat the alien menace, and eventually uncover how to defeat them.

A screenshot of the tactical gameplay

Gameplay switches to its tactical combat phase whenever X-COM ground forces come in contact with aliens. In the Battlescape screen the player commands his soldiers against the aliens in an isometric turn-based battle. One of three outcomes is possible: either the X-COM forces are eliminated, the alien forces are neutralised, or the player chooses to withdraw. The mission is scored based on the number of X-COM units lost, civilians saved or lost, aliens killed or captured, and the number and quality of alien artifacts obtained. Troops may also increase in rank or abilities, if they made successful use of their primary attributes (e.g. killing enemies). Instead of experience points, the combatants gain points in skills like Psi or Accuracy, a semi-random amount depending on how much of the action they participated in. In addition to personnel, the player may use unmanned ground vehicles, outfitted with heavy weapons and armour but not gaining experience. Recovered alien artifacts can then be researched and possibly reproduced. Captured live aliens may produce information, possibly leading to new technology including psionic warfare.
The game has eleven fictional races of aliens. Each race has various strengths and weaknesses, and some races are dependent on other races. The aliens come to Earth from a large base on Mars, but their origins are unknown. One reason for the game's success is the strong sense of atmosphere it evokes. Soldiers are vulnerable to alien attacks even when armoured, and the use of features such as night-time combat, line of sight and opportunity fire allows for alien sniper attacks and ambushes. The enemy comes in numerous forms, and players run into new, deadly aliens repeatedly without any knowledge of their characteristics and capabilities beforehand.
The game may end in several ways. If the player's performance is poor for two consecutive months, the player runs a deficit for two consecutive months, all the player's bases are captured, or the player mounts an assault on the aliens' main base and loses, the game ends in defeat. If, however, the player is victorious in the final attack, the game ends in mankind's victory.
Unofficial game editing software is available allowing players to change the qualities of weapons and equipment, and to change the standard maps and layouts of UFOs that were provided with the game. Fan-made patches also fix a bug which results in the player always playing the game on the easiest difficulty, no matter what difficulty level has been selected (which was not fixed in the official patches).