* Supported OS: Windows® 7 / Vista / Vista64 / XP
* Processor: Pentium 4 3.0GHz
* Memory: 1 GB for XP / 2GB for Vista
* Graphics: DirectX 9 compatible video card with 128 MB, Shader model 2.0. ATI X800, NVidia 6600 or better
* Hard Drive: At least 7.5 GB of free space
* Sound Card: DirectX 9.0c compatible sound card

Recommended:

* Supported OS: Windows® 7 / Vista / Vista64 / XP
* Processor: Intel core 2 duo 2.4GHz
* Memory: 1 GB for XP / 2GB for Vista
* Graphics: DirectX 9 compatible video card with Shader model 3.0. NVidia 7600, ATI X1600 or better
* Hard Drive: At least 7.5 GB of free space
* Sound Card: DirectX 9.0c compatible sound card

Как стало видно по системным требования игра, сделана на так называемой новой версии движка Source Engine. В народе её называют просто - Source Engine для Left 4 Dead 2.