A single player campaign. You must fight your way to the surface of Black Mesa...
Thought the mod was nice. A bit shorter than I thought. Also the fade to black ending wasn't what I expected for an ending (I guess that it will continue with Residual Live) :).
Also noticed the 7.x rating, went and saw the only #1 ratings were from ****, and one person that actually gave a semi-decent reason. Oh well, thats the internet today.