Game Introduction: SA is a study of extraterrestrial biology biotechnology companies, they privately plan to do some evil, and now you must go to SAC2 base and investigate the theft of antibody ~ Dick, your code is 21, Emma, the code you are 12 ... Back on the fourth follow-up story, Emma disappeared, Dick alone to go looking for her ... the first person 3D shooting game Double cooperation, very cool, very fun ~ Play: Players 1, Waterloo mouse shooting, player 2, enter key . In addition to the fourth shot, the more some rich puzzle elements, look right and press the Enter get some tips. (Note: Game has 6M, load please be patient, get stuck, please refresh or change lines)