This is something I've wondered at since I first played Half-Life, and I'm still pretty much in a wut state, so to speak. So, uh, It's about teleporters.. and Black Mesa.. and Gordon. Yeah, I think you've got the general idea.
No? OK, so let be break it down - does anyone know how the Lambda teleport was set up, in terms of entities? I have my theory, but have never tried it out to see if it really works. Is the player teleported into a tight room textured with a "white" texture and lit in green? And then a trigger in that same room activates the trigger_changelevel entity to load the Xen level?