Abandonware that requires online connection for playing online. Progression gatekept by online play, with 28 people playing this is next to impossible. Dead game, do not buy.

PROS:
Flawless gameplay,
Source Engine physics,
Graphics are easy to handle on any PC,
Excellent characters,
Brilliant voice acting,
Wonderful puzzles,
Spectacular storyline,
Mind-blowing setpieces,
Perfect soundtrack,
Awesome Co-Op gameplay,

CONS:
Hats

FINAL ASSESSMENT:
This is undoubtedly the greatest Valve game, you cannot call yourself a gamer if you don't have it. Almost everything about this game is perfect.