Windows
Minimum:
OS: Windows 7 (32/64-bit)/Vista/XP
Processor: 1.7 GHz Processor, requires support for SSE
Memory: 1024 MB RAM
DirectX: Version 8.1
Network: Broadband Internet connection
Storage: 4 GB available space
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
Network: Broadband Internet connection
Storage: 4 GB available space
Sound Card: OpenAL Compatible Sound Card