Uh .... ok.
So, I seem to remember that the objective of the game was to stop a monster/alien invasion caused by a scientific experiment gone bad. Among the many creatures you come across is one called a "headcrab." In fact, it's the first creature you encounter in the game, and near the end (in one of the bigger and more difficult fights in the game), you lock horns with the Big Momma Headcrab. To quote Wikipedia, "they are the most numerous and arguably iconic aliens in the series." One of the behaviors exhibited by headcrabs is that they like to munch on the heads of scientists and turn them into zombies, who then tend to come after you. Since your character happens to be a scientist, this ends up presenting a double threat to you. Maybe they should have called the game "Headcrabs"?
So, I seem to remember that the objective of the game was to stop a monster/alien invasion caused by a scientific experiment gone bad. Among the many creatures you come across is one called a "headcrab." In fact, it's the first creature you encounter in the game, and near the end (in one of the bigger and more difficult fights in the game), you lock horns with the Big Momma Headcrab. To quote Wikipedia, "they are the most numerous and arguably iconic aliens in the series." One of the behaviors exhibited by headcrabs is that they like to munch on the heads of scientists and turn them into zombies, who then tend to come after you. Since your character happens to be a scientist, this ends up presenting a double threat to you. Maybe they should have called the game "Headcrabs"?