Its perfect original it was the frist cod that introduced slide if this game dint exist the cod as we know would be kida broing whitout slide but it dint copy off of zombies it went whit extinction which i think is so fun and has the teeth system you cant buy them so its not buy to win with alot of games are nowadays and it gets boring fast bc of buy to win i have not been bored playing the same maps of extinction bc of this amd the diversity of aliens in it is so good bc it gets harder the father you get in and some games need to take notes of this then i keep beating the campaign and i get sad to know there is no second one and it leaves is off on a cliff hanger makes it more sad we need a cod ghost 2