Half-Life - Uplink

Uplink features many of the common enemies, characters, and weapons from the full game, but unlike the first Half-Life demo and the Half-Life 2 demo, the location and scenario in this demonstration does not appear in Half-Life. The Uplink chapters were cut during Half-Life's development phase and roughly fit in prior to or during the Lambda Core chapter; they were, however, strongly revised for the demo release. Uplink also includes the same Hazard Course from the full release of Half-Life.
Per the opening caption, the player takes control of the main character, Gordon Freeman, 48 hours after the "containment failure," in the Lambda Reactor Complex. The facility is under heavy bombardment. Gordon soon meets a scientist and a security guard who wish to enter the Lambda complex and escape, but they cannot open the reactor door until a signal is sent to the United States Nuclear Regulatory Commission (USNRC), and the radio antenna must be reconfigured manually. To this end, they enlist Gordon Freeman's aid. He moves through an area populated by headcrabs, zombies, and vortigaunts with the help of another security guard, and then battles HECU personnel, who are executing scientists. He then moves through a HECU camp, battling many soldiers and a few military turrets. Gordon soon arrives at the building containing the radio antenna and sends a message to the USNRC. After an ambush by HECU personnel busting through the roof and door of the building, Gordon passes through a maze-like area containing numerous radiation leaks, as well as a dying scientist due to radiation poisoning. Gordon also encounters zombies and barnacles, who are killing the last few HECU troops in the building. Freeman climbs out and arrives back at the HECU camp, where more HECU soldiers have arrived, although they are preoccupied with fighting vortigaunts.
Upon defeating the Vortigaunts, the remaining soldiers attack Gordon, who defeats them. He meets the security guard who helped him through the area the first time he was there, but (unless the player ordered him to wait for him at another place) the guard is ambushed and killed by Vortigaunts. Gordon presses through the area, battling vortigaunts, headcrabs, and zombies. He soon arrives at the area where the scientist and security guard waited for him. Headcrabs have found their way into the area, but the security guard defeats them. The three men open the reactor door and push towards the Lambda complex.
Gordon, the security guard, and the scientist push towards the Lambda complex and battle Xen creatures. They encounter a still-conscious scientist being infested by a Headcrab, and Gordon may mercy-kill him. After battling a pack of houndeyes, part of the building collapses, which does not harm the security, Gordon, or the scientist, but separates Gordon from the security guard and the scientist. He continues to press on towards the Lambda complex and finds his way in after a vent collapses due to a gargantua's roar.
Gordon enters the Lambda complex, and three scientists (one wounded) and a guard are there as well. Soon, the Gargantua heard before attacks and kills all four people in the room, and traps Gordon, who cannot defeat it without explosives, and cannot escape. As the Gargantua closes in on Gordon, the G-Man is seen watching from a window, straightening his tie, and walking away. The screen then fades to black, accompanied by the caption: Current evaluation: uplink completed. Require further data.