Unfortunately I can’t remember which of the two levels I was playing, but I happened upon an elevator and then realized there was a grate that let me take ANOTHER path that involved lots of ladders (with a fall at the bottom), and a music track that I don’t believe would have played had I taken the elevator.
Was this path in Half-Life or added by the Black Mesa team? I was just curious because it was a moment that stood out to me and I know that you guys can answer this question for me XD.