Operation: Black Mesa is a fan remake of two additions to the first Half-Life - Half-Life: Blue Shift and Half-Life: Opposing Force. The shooter features more than 18 types of weapons, over 30 types of enemies, the Source engine and much more. You will play as security guard Barney Calhoun and Corporal Adrian Shepard. In addition, the game has a new soundtrack and the ability to create your own modifications.