PC System Requirements:
Processor: 1.5GHz
RAM: 256MB (512MB recommended)
Video card: 32MB 3D-accelerated video card (64MB recommended)
DirectX 9

Mac System Requirements:
OS: Mac OS X 10.5 or newer
Processor: 2.0 Ghz Intel or equivalent
Memory: 2 GB RAM
Video Card: 256 MB NVidia or ATI graphics card
Not recommended for: Macs with integrated graphics

Supported platforms include Steam, PC, Mac, Wii, PS3/PSN.

ESRB