An innovative co-op game that makes proper use of the 'teamwork=survival" formula.
Emphasis on mulitplayer-
This game is most fun when you play with friends, either online of off. the downside to this is that you may feel detached from the game if you only play this on your own. In fact I would recommend you only buy it if you are set up for multiplayer.
Survival-
That aside, when you play through the campaign with friends you become immersed in a fight for survival, one which draws you in even further which each increased difficulty level. All players must work as a team, or you die, it is as simple as that. Those that stray usually end up dead. Ammunition is usually in good supply but health is not, meaning you will have to work as a team to stay alive as best you can, just like you see in the movies.
Innovation-
-Zombies can attack you from anywhere, Valve have come up with the 'Zombie Director', which means that zombies with have a random spawn point each time you play. Hordes of zombies can come from anywhere any time as a result, and no two experiences are the game. This makes up for the fact that there are only four campaigns 'chapters' or scenarios for you to play through.
Teamwork-
-Certain zombies can constrict you or pin you down and it takes a team mate to get you out of certain sticky situations, believe me it can be very nerve wracking when you get dragged away from your teammates by a zombie!. Team mates are also required to revive you further increasing the need to work together, especially on harder difficulties(I've only managed Advanced so far!).
Some bad-
There is a small selection of weapons. There are only four campaign chapters. Playing on your own isn't half as fun.
I short-
It is easy to overlook the shortcomings mentioned above. If you are into multiplayer shooters, and like the 'zombie and fight for survival' genre then this game will provide ample fun.
Thanks for reading.