I played it in dark room. I might add that all those years ago I either didn't understand the story at all, or I had nerves of steel. The game is god damn scary, especially when you go through dark pipes, and you clear zombies on the other side... And I don't even want to consider how Gordon feels!
It's amazing how games have changed since the 1990's. I miss the 'old school' shooters like HL. I guess today's generation prefers playing Tag with guns.
I never finished the original HL. I got stuck on the dexterity-required puzzle where Gordon has to jump from one spinning centrifuge to the next to get past the section. At least I think that was what was going on. My memory has faded a bit since I played it years ago.