Can you talk a little bit more about how the whole train thing came about in the intro of Half-Life 2?
ML: It was a code thing. One of the level designers was constantly asking for more features they could use in the level editor, and trains are sort of a general-use thing. Every time a platform moves in Quake, that was a type of train. Usually they just go back and forth, and they didn't move very smoothly. So one of the programmers on Half-Life created a track train that would move over long distances and turn and pivot on certain points and go around curves and certain things like that.
I don't remember what the original request was for what the original level designer had in mind, but I remember when I heard about it, the first thing that came to my mind was an actual train. I just took it too literally, and I started thinking in terms of, "What could we do with a train in Half-Life?"
It's well worth a read.
