Spherical Nightmares is a Half-Life 2: Episode Two single-player modification. The story takes place in the Half-Life universe and you take the role as Gordon Freeman. Your journey begins in an unknown location.
A decent-ish mod, filled with competent gun fights, puzzles, and adequate pacing. Story starts off intriguingly but quickly fizzles out in favor of pretty much non-stop action, which is disappointing. There's some nifty set pieces, though - particularly the tram sequence. Everything else is pretty much run-of-the-mill but, as I said, competent enough.
Ended very abruptly and left me feeling very cold about the whole thing. I get the feeling you can do so much better.