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BEFORE STARTING ANY OF THE STEPS OF THE ADDON CREATION PROCESS, MAKE SURE YOU HAVE DOWNLOADED THE LEFT 4 DEAD 2 AUTHORING TOOLS FROM STEAM.

To do this, follow these 4 steps:

• Click on "Library" on the top left corner of the Steam application window, and then select "Home" from the dropdown menu
  
• Click on the Box above the search bar on the upper left hand side of the Steam window, and click on the row which has the title "Tools" to make sure it has a blue check mark on its left side
  
• Use the search bar above the list of applications or scroll down until you see "Left 4 Dead 2 Authoring Tools"
  
• Right or left-click on "Left 4 Dead 2 Authoring Tools" and then click "Install" and go through the process to install the tools

Downloading the Left 4 Dead 2 Authoring Tools will allow you to package your addon folder for use in-game and upload your addon to the Steam workshop, so they are essential for this tutorial.
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You will first want to download 2 programs before you start creating the addon:

• Audacity - [https://shorturl.gg/ZxDLS]
  
• GCFScape (non-essential; to look into and copy files from VPKs) - [https://shorturl.gg/apzr]

You may also need to download these tools if GCFScape has problems:

• Microsoft Visual C++ 2010 SP1 Redist. Package x86 (32 bit OS) - [https://shorturl.gg/ciBpX]
  
• Microsoft Visual C++ 2010 SP1 Redist. Package x64 (64 bit OS) - [https://shorturl.gg/f63Y]
  
• Microsoft .NET Framework - [https://shorturl.gg/GOHVkf]

You can find all the sound files by going to steam → steamapps → common → Left 4 Dead 2 → left4dead2 (plus its dlc folders) and opening the "sounds" folder within there.

Now create a folder path leading to the sound file(s) you want to replace. For example, if you wanted to replace the impact and swing sounds for the Machete, you would create this folder path: ([your addon name] → sound → weapons -> machete) Also make sure to include the specific sounds you are going to replace within your addon folder path, in their proper locations.

Afterwards, find the sound that you want to replace the default sound, and have it ready for the next part of the addon-making process.

• Open Audacity and load in both the sound you want to replace and your custom sound by either dragging both sounds into the program, by going to File → Import and then clicking "Audio" in the list, or by going to File → Open
  
  
• Make the format and sample rate of the custom sound the same as that of the sound which it is replacing, and make sure the custom sound is the same length as the original sound
  
  
• Delete the original sound that is being replaced, and then go to File → Export and save the audio file that you are exporting as the same file type of the file you are replacing. Save this custom sound to the same location of the sound that you are replacing

• Drag your addon folder into vpk.exe, which is located at steam → steamapps → common → Left 4 Dead 2 → bin → vpk.exe (I recommend making a shortcut of vpk.exe somewhere that's it's easy and convenient to access) A .vpk (Valve package) file of your addon folder will then be created in the same area that vpk.exe (or its shortcut) is located
  
  
• Drag the .vpk file of your addon into the folder "addons", located at steam → steamapps → common → Left 4 Dead 2 → left4dead2 -> addons
  
  
• Test your custom flashlight in-game

Addon Details

• Create a text file called "addoninfo" and set it up like this (copy&paste text block below):
  
  "AddonInfo"
  {
  addonSteamAppID 550 ------ (don't change; ID is specific to Left 4 Dead 2)
  addontitle "title goes here"
  addonversion version number goes here (1,2, etc.)
  addonauthor "author goes here"
  addonDescription "description goes here"
  }
  
  
• Place the addoninfo file into the main folder of your addon (e.g. addon name → addoninfo)

Addon Image

• Find an image of your choosing (.jpg and .png for example) and name it "addonimage"
  
  
• Place this image within the main folder for your addon

Open the Left 4 Dead 2 Authoring Tools Steam app

Click the "+" symbol or go to File → Publish New Add-on

Select the .vpk file of the addon that you want to upload to the workshop, title the addon, and add an image for it. Add a description and tags as well if you feel like it

Accept the terms of the Steam License Agreement and click on the "Upload" button on the in the bottom right area of the window