Half-Life: Blue Shift

Half-Life: Blue Shift is an expansion for Half-Life following a security guard through the Black Mesa disaster. Though Blue Shift was made after Opposing Force, it does not have most of the code or content from that game, but Blue Shift does have some new and unique things of its own.

The name "Blue Shift" refers to a phenomenon of the same name seen in astrology, where the light waves emitted by objects become shorter (therefore bluer) as they move towards the viewer.