The PS2 had a small campaign attached too called Decay. http://en.wikipedia.org/wiki/Half-Life:_Decay It was a co-operative campaign with each player taking the role of a Black Mesa scientist. It introduced a character who was in Blue Shift too. Recently it has been ported to pc as well. Blue Shift was developed for DC first and then to PC. Notice that in the DC version if you smash open crates you'll see VMU's and other DC bits. In the PC they are changed but there is a short command to change it IRC.