Uplink

Half-Life: Uplink is a demo version of Valve Software's 1998 first-person shooter computer game Half-Life, released on February 12, 1999. Uplink features many of the common enemies, characters, and weapons from the full game, but unlike the first Half-Life demo (Half-Life: Day One) and the Half-Life 2 demo, the location and scenario in this demonstration do not appear in Half-Life. Day One is an OEM version that features roughly the first fifth of the entire game. The Half-Life 2 demo features two selectable chapters taken directly from the game. Like its successor's demo, however, Uplink was made available for download after the release of the full retail version of the game.

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.

Uplink was included with the Game of the Year Edition of Half-Life as a mod, and was included with all subsequent releases. While absent from Steam, Uplink can still be installed if the user has access to the Uplink files from a previous Half-Life install, through Uplink Lite or through Uplink Addon, which seamlessly adds the Uplink levels into the gameflow of Half-Life itself.

Story
The player takes control of Gordon Freeman 48 hours after the "containment failure," according to a caption. A scientist and a security guard 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 the player's aid, sending him through an area heavily populated with military personnel and Vortigaunts; having reconfigured the antenna, the player must navigate through an underground maze populated by headcrabs and zombies.

Arriving back at the starting point, the player passes through the previous area, fighting against headcrabs, zombies, and now houndeyes, only to become trapped in a large room with a Gargantua, which proceeds to kill everyone there before homing in on the player. The G-Man is seen watching from a window high on the wall. The screen then fades to black, accompanied by the caption: Current evaluation: uplink completed. Require further data.