Area 51: Site 4

The game is broken down into two big menus: field exercise and adventure. The training levels are based on brief missions where the player must complete all "training challenges" and the "real mission" (in either order). Completing all the training challenges will involve shooting zombies that are contained in the labs, shooting giant maggots trying to burrow into sick patients in an infirmary, protecting a bus from aliens trying to roll it over, turrets, and missiles. (wiki)