Windows
Minimum:
OS: Windows 7 / Vista / XP
Processor: 3.0 GHz P4, Dual Core 2.0 (or higher) or AMD64X2 (or higher)
Memory: 2 GB RAM
Graphics: Video card must be 128 MB or more and with support for Pixel Shader 2.0b (ATI Radeon X800 or higher / NVIDIA GeForce 7600 or higher / Intel HD Graphics 2000 or higher).
DirectX: Version 9.0c
Storage: 8 GB available space
Sound Card: DirectX 9.0c compatible
SteamOS + Linux
Minimum:
OS: Ubuntu 12.04
Processor: Dual core from Intel or AMD at 2.8 GHz
Memory: 2 GB RAM
Graphics: nVidia GeForce 8600/9600GT, ATI/AMD Radeon HD2600/3600 (Graphic Drivers: nVidia 310, AMD 12.11), OpenGL 2.1
Storage: 8 GB available space
Sound Card: OpenAL Compatible Sound Card