THE OWL’s Sandbox
The old tutorial was obsoleted by DLC2. This is the new method, as described by Lpfreaky90 and Felix Griffin.
Step 1
Create a folder for your mod in
Sandbox Navigation
Redesign Preview
Colors
Typography
Typeface
sans-serif (general)
monospace (for code)
Inline Code (T)
$basetexture
Keyboard Key (T)
Ctrl
Iconography
It’s empty here for now.
Buttons
It’s empty here for now.
Selectors & Elements
Checkbox
It’s empty here for now.
Toggle button
It’s empty here for now.
Tabs (T)
Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.
and rename it to the name of your mod. Open that folder and create two subfolders: "cfg" and "maps".
Step 2
Open the "maps" folder and create a folder called "soundcache" inside it. Copy the file called "_master.cache" from
Sandbox Navigation
Redesign Preview
Colors
Typography
Typeface
sans-serif (general)
monospace (for code)
Inline Code (T)
$basetexture
Keyboard Key (T)
Ctrl
Iconography
It’s empty here for now.
Buttons
It’s empty here for now.
Selectors & Elements
Checkbox
It’s empty here for now.
Toggle button
It’s empty here for now.
Tabs (T)
Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.
to this new soundcache folder.
Step 3
Create a gameinfo.txt file in your mod's root directory. Use this template:
"GameInfo"
{
game "Your Mod's Name"
GameData "portal2.fgd"
FileSystem
{
SteamAppId 620 // Portal 2 has ID 620
SearchPaths
{
Game |gameinfo_path|.
Game portal2_dlc2
Game portal2_dlc1
Game portal2
}
}
}
Step 4
Use a program like 
GCFScape to open
Sandbox Navigation
Redesign Preview
Colors
Typography
Typeface
sans-serif (general)
monospace (for code)
Inline Code (T)
$basetexture
Keyboard Key (T)
Ctrl
Iconography
It’s empty here for now.
Buttons
It’s empty here for now.
Selectors & Elements
Checkbox
It’s empty here for now.
Toggle button
It’s empty here for now.
Tabs (T)
Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.
and copy the file called
Sandbox Navigation
Redesign Preview
Colors
Typography
Typeface
sans-serif (general)
monospace (for code)
Inline Code (T)
$basetexture
Keyboard Key (T)
Ctrl
Iconography
It’s empty here for now.
Buttons
It’s empty here for now.
Selectors & Elements
Checkbox
It’s empty here for now.
Toggle button
It’s empty here for now.
Tabs (T)
Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.
to
Sandbox Navigation
Redesign Preview
Colors
Typography
Typeface
sans-serif (general)
monospace (for code)
Inline Code (T)
$basetexture
Keyboard Key (T)
Ctrl
Iconography
It’s empty here for now.
Buttons
It’s empty here for now.
Selectors & Elements
Checkbox
It’s empty here for now.
Toggle button
It’s empty here for now.
Tabs (T)
Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum. . Edit it, then pack it into a new VPK using
Sandbox Navigation
Redesign Preview
Colors
Typography
Typeface
sans-serif (general)
monospace (for code)
Inline Code (T)
$basetexture
Keyboard Key (T)
Ctrl
Iconography
It’s empty here for now.
Buttons
It’s empty here for now.
Selectors & Elements
Checkbox
It’s empty here for now.
Toggle button
It’s empty here for now.
Tabs (T)
Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.
or GCFScape.
Step 5
Restart Steam. If it all worked, your mod should be listed. Congratulations!