Gamma Energy v1.1 (ZIP version) file

I know I'm 2 years late but it's because this mod is very old - it's simply not compatible with the steam version of portal anymore. You'd need to download the "source unpack" version of portal.

How ?

Just paste this to gameinfo.txt in the mod directory

"GameInfo"
{
game "Gamma Energy"
title "Gamma Energy"
type singleplayer_only
nodifficulty 1
hasportals 1
icon "resource/gameicon"
FileSystem
{
SteamAppId 400 // This will mount all the GCFs we need (240=CS:S, 220=HL2).

//
// The code that loads this file automatically does a few things here:
//
// 1. For each "Game" search path, it adds a "GameBin" path, in <dir>\bin
// 2. For each "Game" search path, it adds another "Game" path in front of it with _<langage> at the end.
// For example: c:\hl2\cstrike on a french machine would get a c:\hl2\cstrike_french path added to it.
// 3. For the first "Game" search path, it adds a search path called "MOD".
// 4. For the first "Game" search path, it adds a search path called "DEFAULT_WRITE_PATH".
//

//
// Search paths are relative to the base directory, which is where hl2.exe is found.
//
// |gameinfo_path| points at the directory where gameinfo.txt is.
// We always want to mount that directory relative to gameinfo.txt, so
// people can mount stuff in c:\mymod, and the main game resources are in
// someplace like c:\program files\valve\steam\steamapps\half-life 2.
//
SearchPaths
{
// First, mount all user customizations. This will search for VPKs and subfolders
// and mount them in alphabetical order. The easiest way to distribute a mod is to
// pack up the custom content into a VPK. To "install" a mod, just drop it in this
// folder.
//
// Note that this folder is scanned only when the game is booted.
game+mod portal/custom/*

// Now search loose files. We'll set the directory containing the gameinfo.txt file
// as the first "mod" search path (after any user customizations). This is also the one
// that's used when writing to the "mod" path.
game+mod+mod_write+default_write_path |gameinfo_path|.
gamebin |gameinfo_path|bin

// We search VPK files before ordinary folders, because most files will be found in
// VPK and we can avoid making thousands of file system calls to attempt to open files
// in folders where they don't exist. (Searching a VPK is much faster than making an operating
// system call.)
game_lv portal/portal_lv.vpk
game portal/portal_sound_vo_english.vpk
game portal/portal_pak.vpk
game |all_source_engine_paths|hl2/hl2_textures.vpk
game |all_source_engine_paths|hl2/hl2_sound_vo_english.vpk
game |all_source_engine_paths|hl2/hl2_sound_misc.vpk
game |all_source_engine_paths|hl2/hl2_misc.vpk
platform |all_source_engine_paths|platform/platform_misc.vpk

// Add the HL2 directory as a game search path. This is also where where writes
// to the "game" path go.
game+game_write portal

// Where the game's binaries are
gamebin portal/bin

// Last, mount in shared HL2 loose files
game |all_source_engine_paths|portal
game |all_source_engine_paths|hl2
platform |all_source_engine_paths|platform
}
}
}