Half Life: Southwest mod for Half-Life

This is my first mod, and is a prequel to the original Half-Life. The year is 1968 (yes a little change in the story) (thirteen years after Black Mesa fundation, and long before the incident) and within a facility called Black Mesa Southwest, located in Arizona, U.S.A. You control Franklin Alexander a contracted agent by Black Mesa. In laboratories they began making the first prototypes of portals to teleport and teleport creatures of alien planets. But the facility receives a threat by the terrorist group called White Operations and said it would destroy the facility and would steal the portals. Your mission is to kill all the terrorists and stop them from destroying Black Mesa Southwest. Sorry for my bad english.