The player takes control of Barney Calhoun, a security officer briefly seen during the opening of the first game. While making his usual rounds at Black Mesa, the Resonance Cascade teleports an influx of alien creatures into the facility. Using what little equipment he has available, Barney travels through the facility and recruits the help of Dr. Rosenberg, who has a plan to transport the trapped scientists safely out of Black Mesa.
Compared with its predecessor Half-Life: Opposing Force, Blue Shift is considerably stripped back in terms of content, lacking many of the weapons and enemies from the original game and unlike Opposing Force featuring no new enemies or weapons of its own. Blue Shift was the first game in the franchise to have a significant NPC helping the player during the game, and the game came with a free High Definition pack that upgraded the models to the source game. Barney would later go on to become a major supporting character in Half-Life 2.
In March 2021, Black Mesa Blue Shift, a comprehensive Fan Remake that recreates the entire expansion pack as a mod for Black Mesa, had its first chapter released. As of August 2021, two playable chapters have been released so far.
Half-Life: Blue Shift contains examples of:
- Action Survivor: Barney Calhoun, especially when compared to Gordon. Both men spend a lot of their time trying not to get killed by the aliens and the HECU forces but where as Gordon becomes an Action Hero, Barney's story is all about getting out of Black Mesa alive and not having to risk his life for extra reasons outside of his control. Calhoun also ultimately faces significantly less opposition than Freeman or Shephard, mostly only facing Xen wildlife, Vortigaunts, and Marines, with only about 4 Alien Grunts and 6 Controllers ever crossing his path. In addition, he doesn't get an HEV suit or HECU equivalent; instead, he has a run-of-the-mill vest. His weaponry is limited, too.
- Armies Are Evil: The HECU are once again shown in a negative light when they imprison and mercilessly execute scientists and security personnel as part of their Fiery Coverup mission.
- Ascended Extra: Barney Calhoun himself. He goes from a random security guard banging on a door in Half-Life to a fully playable character with his own story.
- Bittersweet Ending: Calhoun, Rosenberg, Simmons, and Walter make it out of the facility alive and well, and escape in a Black Mesa SUV. However, several other surviving security personnel and scientists helping them to escape are killed in the process.
- Black Dude Dies First: The first onscreen casualty is a grouchy black scientist who asks Barney to fix up the elevator by using an electric panel. When the incident starts, the panel explodes, killing said scientist.
- Boss Battle: Averted, as this is the only Half-Life game without any boss fights. The game doesn't even have a Final Boss, with 2 houndeyes and a 4-man squad of Marines being your only opposition during the final sequence in which you power up the teleporter to escape Black Mesa.
- Cavalry Betrayal: Calhoun finds out early on that the military unit sent to Black Mesa to contain the Alien Invasion, the HECU, is not on their side, when he witnesses a couple of Marines disposing of the bodies of scientists and security guards into a drainage pipe.
- Continuity Nod: On the initial train journey in Half-Life 1, you pass by a security guard banging on a door. In Blue Shift, the first door you come to malfunctions, and if you look around while waiting for the guard on the other side to open it, you'll see Freeman passing you by. Later on, you can overhear some marines complaining about having to do the crap work because Shephard's team hasn't arrived yet.
- Creator Cameo: In "Captive Freight" when you're traveling through the tunnels before reaching the train-yard, you will come across an opened box that just so happens to have gear shaped objects spilling onto the floor. Aka, a gearbox.
- Developers' Foresight:
- During the ''Captive Freight" level, you come across two scientists in your search for Dr. Rosenberg. If you actually try to backtrack with these two scientists following, you would come to realize that there is an invisible wall that will not allow the scientists to walk any further. That's because if you were able to backtrack far enough, you would come across the breakable wall that you would eventually learn about from Dr. Rosenberg that leads to where his colleagues are creating the portal device to escape Black Mesa. The reason for the invisible wall was so that you couldn't break the story and have two random scientists waiting at the elevator when Dr. Rosenberg leads you to it later on in the story.
- If the player destroys the wall hiding the elevator to the portal chamber before Dr. Rosenberg leads you back to it, you will soon realize that he will have a different line-of-dialogue regarding the fact that Calhoun has already found the hidden elevator instead of the normal dialogue to destroy the wall.
- Disconnected Side Area: When Barney makes it to the surface for the first time, a tunnel labeled "South Exit" is barricaded and its keypad is sabotaged. At the endgame, Barney and Dr. Rosenberg's team teleport to the other side of this tunnel to finally leave Black Mesa.
- Donut Mess with a Cop: The fat security guard in the firing range is seen trying to reach for his holstered gun while holding a donut with the closer hand. Later, a scientist tells another guard "Shouldn't you be off guarding some coffee and donuts?"
- Drought Level of Doom: Xen can be this, as there are no armor pickups anywhere (which makes sense, as the HEV-wearing expedition teams would have had no reason to bring any, since there's no reason for a security guard to be on Xen) and ammo is relatively spaced apart and only found on dead expedition team members, who usually only carry about a mag each for your basic weapons. On the plus side, the healing pools provide infinite health regenerate. Going in with full armor and ammo is very helpful.
- Earn Your Happy Ending: Compared with the other Half-Life games, Blue Shift at least affords Barney a happy ending, though it's not easy.
- Elevator Failure: Calhoun's first assignment is to fix an elevator in Sector G. When he does, the elevator makes it down a few floors before the Resonance Cascade causes it to drop rapidly to the bottom of the shaft. Calhoun is the only one to survive the impact.
- Just Train Wrong: Besides the typical Black Mesa monorails there are also a few conventional platform cars on standard tracks which are just a flat texture on the ground. Many of the cars are carrying containers but in real life containers are loaded on dedicadet cars. Two of the cars are just stuck together with no clearance between them so you can't even see if there's a coupler between them. The cars are hardly wider than the rail gauge except a single platform car carrying a tank whichnote in turn is too wide to pass through the relatively narrow tunnels. There is a single yard with a turntable but the turntable can herdly contain a single car so it would require at least two switchers on different tracksnote but there is only one. Not that it matters much since none of the tracks seem to lead anywhere.
- Let Us Never Speak of This Again!: In the ending, the G-Man's status report for Calhoun reeks of embarrassment due to Calhoun and Rosenberg escaping Black Mesa. He was likely too busy keeping tabs on Gordon and Shephard's progress.Subject: Calhoun
Status: Out of Range
No Further Comment
- Powered Armor: For once, averted. Unlike the Black Mesa Science Team or the HECU, who are provided the HEV Suit and PCV for use in Hazardous Environments, the members of the Black Mesa Security Team are only provided conventional helmets and body armors. While it does protect its user from gunfire, explosives, and some environmental hazards, it becomes worn out over time and cannot be recharged. Instead, the only way to get armor back is to pick up a new vest and helmet.
- Previous Player-Character Cameo: Gordon Freeman is first seen boarding and then riding the tram not long after Calhoun makes it to the entrance of the Security Office he's assigned to. Later, during the ending, he witnesses Freeman being captured by the HECU while Calhoun is stuck in a harmonic reflux.
- Scenic Tour Level: Just like the other games, the game opens with Barney making his way to an elevator while passing through security.
- Screw This, I'm Outta Here!: The whole plot of the game following the Resonance Cascade. Justified, as Calhoun and later Rosenberg realize that the extent of the disaster is just too much for them to handle, and they decide, with help from other surviving scientists, to just get out of Black Mesa entirely, and let the Lambda Team and Freeman deal with the mess instead.
- Title Drop: "Blue Shift" is the In-Universe name of the security shift that Barney works on.
- Working-Class Hero: In contrast to Gordon Freeman and Adrian Shephard, Calhoun has no doctorates nor specialized military training, relying solely on his basic training as a security guard in order to survive and get out of Black Mesa.