Power Up is the seventh chapter of Half-Life.
The chapter takes place in Track Control in Sector E. Here, the player encounters a large alien creature called Gargantua, which acts as a boss character, and can not be killed by conventional means. The dying security guard in the track control room has an escape plan. The player needs to restore the power to the rail system, so the player can ride the rail cart to the surface and escape. The path to the power generator is populated with Marines and aliens. After restoring the power, the player can kill the creature by luring it into the transformers supplying the power to the rail system.
The chapter did exist in some form in the 1997 version of the game. It can be seen in two early screenshots, one showing the maintenance shaft in the map c2a1b, and other showing the stairs to the generator area in the map c2a1a. There are two inaccessible rooms with fans in the generator area in the map c2a1a. These rooms were originally connected to the maintenance area with the water pump with no walls between them.
The console ports features some minor changes. There are fewer enemies in some areas. The rail cart room is blocked until the power to the rail tracks is restored in the PlayStation 2 version. The level code for the chapter is "Big Is Beatiful" in the Dreamcast version.
Behind the scenes
The original chapter title was Footfall. Unused Black Mesa Announcement System lines for the chapter can be found in the sentences file used for the speech system. The name of the chapter is "Track Control, Sector E" in the document.
There were to be numbers on the tunnel entrances (as decals) at the beginning of the chapter. The number 047 on the left, and the number 042 on the right. They appear as entities in the map files, but weren't placed on any surface. There is crossbow ammo in one of the breakable crates in the map c2a1b, even though the weapon is not obtainable until the chapter Apprehension. There is a "world_items" object, a generic item entity, in the map c2a1a with its item number value set to 36. This item value is not defined in the game or the source code, so nothing is spawned.
The Gargantua is heard screaming throughout the chapter. The area shakes and debris falls from the ceiling each time when it happens. According to Dario Casali, the designer of the map, this was inspired by Jurassic Park, the movie. There is a couple of unused animations showing the Marines getting killed by a Gargantua in various ways. These include Gargantua throwing a Marine backwards in a tunnel, crushing a Marine with a punch, grabbing and throwing away a Marine, and biting off a Marine's head.
Ditto, early version as seen in a Worldcraft tutorial map.