GS: It seems safe to say that Left 4 Dead is a class-based game, considering Turtle Rock's previous work on Counter-Strike: Source, and judging from the early graphic showing the four heroes, each carrying a different type of weapon. What are the classes in the game, and how do they complement one another?MB: From the survivor standpoint, Left 4 Dead is a cooperative game in which success is based upon the skills of each member and the team's ability to work together as a unit. As such, the four survivors have the same weaponry available to them and begin with the same skills.On the infected side, however, the characters available to human players (the boomer, smoker, hunter, and tank) have very specific skills.