In Undead Assault II, there is an exp system that after each game you can save your exp. Then next game you load the exp and depending on the amount of exp you have you get access to new people. You start out with teh trooper and medic and zero exp. Then the more exp you get, the more choices you have. ASo 150 lets you be support. For instance, I played about five games to earn me 1000 exp so I could become a sniper class. He wants to know how to do this type of system. I actually have no clue. I do hop ei explained it well.