So I have just installed Black Mesa, tried to play it through steam, and cannot get further than about 30 seconds into the train sequence!
I can start the train sequence fine, it runs for about 30 seconds, the automated voice tells me about the topside temperature and that the facility is kept at 62 degrees or whatever, then as soon as the train rounds the next corner I get a loading screen and it teleports me to the middle of an outdoor valley with plants and cacti in the sky and what looks like the underground facility floating just off the end of the valley to the right. I cannot move around or do anything exept open and close the menu. I have tried restarting steam several times, and made sure I had the Source SDK base downloaded but I cannot get past the train no matter how I try!