Strategy Evolved: XCOM: Enemy Unknown couples tactical turn-based gameplay with incredible action sequences and on-the-ground combat.
Strategic Base: Recruit, customize and grow unique soldiers and manage your personnel. Detect and intercept the alien threat as you build and expand your XCOM headquarters.
Tactical Combat: Direct soldier squads in turn-based ground battles and deploy air units such as the Interceptor and Skyranger.
Worldwide Threat: Combat spans the globe as the XCOM team engages in over 70 unique missions, interacting and negotiating with governments around the world.

Strategy Evolved: XCOM: Enemy Unknown couples tactical turn-based gameplay with incredible action sequences and on-the-ground combat.
Strategic Base: Recruit, customize and grow unique soldiers and manage your personnel. Detect and intercept the alien threat as you build and expand your XCOM headquarters.
Tactical Combat: Direct soldier squads in turn-based ground battles and deploy air units such as the Interceptor and Skyranger.
Worldwide Threat: Combat spans the globe as the XCOM team engages in over 70 unique missions, interacting and negotiating with governments around the world.

XCOM: Enemy Unknown System Requirements :

Minimum:
OS:Windows Vista
Processor:2 GHz Dual Core
Memory:2 GB RAM
Graphics:NVIDIA GeForce 8600 GT / ATI Radeon HD 2600 XT or greater
DirectX:9.0
Hard Drive:20 GB HD space
Sound:DirectX Compatible
Other Requirements:Broadband Internet connection
Additional:Initial installation requires one-time internet connection for Steam authentication; software installations required (included with the game) include Steam Client, Visual C++ 2008 Redistributable, DirectX and Microsoft .NET 4.

Recommended:
OS:Windows 7
Processor:2 GHz Dual Core (Intel Core 2 Duo 2.4 GHz or Athlon X2 2.7 GHz)
Memory:4 GB RAM
Graphics:NVIDIA GeForce 9000 series / ATI Radeon HD 3000 series or greater
DirectX:9.0
Hard Drive:20 GB HD space
Sound:DirectX Compatible
Other Requirements:Broadband Internet connection
Additional:Initial installation requires one-time internet connection for Steam authentication; software installations required (included with the game) include Steam Client, Visual C++ 2008 Redistributable, DirectX and Microsoft .NET 4.

XCOM: Enemy Unknown installation notes:

1.Install
2.Play

Includes DLC ELITE PACK