In order to modify the game in any way shape or form, there is some things we must do first before setting up the Unity project.

Installing Unity 2021.3.16f1

First off, before doing anything else it is important to have Unity installed on the computer, we will need it later to set up our project.

1. Go to Unity's website and download Unity Hub.

The location of this installation is not important, pick wherever you would like, it defaults to your Program Files directory.

2. Navigate to The Unity archive and press "install"

Making a working copy of ATLYSS

As of the publication of this document, there is nothing that prevents you from moving the game's directory to another location, it is heavily suggested to copy your entire game folder from your steamapps/common directory as to prevent corrupting save files.

1. Pick a location and create a folder, the name isn't important, but it's where we'll be storing tools for our workflow as well as the game copy. Call it something useful, like "MyATLYSSModdingKit"
2. Copy ATLYSS to this folder from steamapps/common

Adding useful tools

1. Create a new folder called "Tools"
2. Extract the latest release of AssetRipper into a folder called "AssetRipper"
3. Extract ILSpy into a subfolder called "ILSpy"

The name of the folders isn't important, it's sufficient to call them whatever you want as long as you can remember where they are!

Creating the Unity Project

1. Open Unity Hub
2. At the top right press "New Project"
3. A new window will open
4. Select the correct editor version from the dropdown at the top of the window, 2021.3.16f1
5. Select 3D (Built-In Render Pipeline) as the template
6. On the right, name your project, something like "ATLYSSUnityEditor" is sufficient
7. Select the location of the directory containing our "Tools" folder
8. Uncheck "Connect to Unity Cloud" to prevent uploading any game assets to the internet incidentally.
9. Select "Create Project" which is the button on the bottom right of the window.

Import ThunderKit

1. In your new Unity project, on the top of the screen, select the "Window" dropdown.
2. Press "Package Manager" to open the Unity Package Manager window.
3. Press "Add package from git URL..."

The Unity Package Manager dropdown

4. To import Thunderkit, use the url https://github.com/PassivePicasso/ThunderKit.git#9.1.0 to install the 9.1.0 version used for this tutorial.

Adding the git URL

5. Wait for ThunderKit to finish installing.

Installing ATLYSS Custom Package

1. When ThunderKit is finished installing, a new window will appear labelled "Settings"
   • Uncheck "Import Addressable Catalog" as it won't do anything here
   • Change "Import Project Settings" Included Settings to "Everything"

The requisite Import Configuration

6. Press "ThunderKit Settings" on the left column and enter your game path and executable by pressing "Browse" on the right.
7. Turn Generate ThunderKit Assets Project and Fix Local Disk Packages to "On" under "Project Generation"
8. Press Import, restart the project when prompted.
9. After the project restarts, and when it is finished importing, restart again when prompted.
10. Validate you now have ATLYSS as a package in your Unity Package Manager

Extracting Game Assets with AssetRipper

AssetRipper is incredibly easy to use, only requiring a few parameter changes to export all the needed assets to compile the game.

1. Open AssetRipper.GUI.Free.exe in Tools/AssetRipper from earlier.
2. A new tab will open labelled "AssetRipper Free"
3. Select "Settings" under "File" on the top left dropdown bar

4. Scroll down to "Export", and change "Script Export Format" to "Dll Export without Renaming"

5. Check the "Save Settings to Disk" box and press the white "Save" button underneath it.

6. On the webpage, select "File" again, "Open Folder"
7. Choose the ATLYSS folder from our directory in the popup window.
8. On the webpage, select "Export" at the top, "Export All Files"
9. When you press the green "Select Folder" button Create a new folder inside the "AssetRipper" directory, call it "AssetRipperOutput" or similar.
10. Use the "Export Unity Project" button to output the game's assets into the folder you just created.

Adding Game Assets to Unity Editor

1. Inside "AssetRipperOutput" is a folder titled "ExportedProject" that contains the data we want to import.
2. Rename the "Assets" folder to "ATLYSS"
3. Inside the same folder, delete the "Plugins" folder, as well as "Editor"

The renamed folder only containing the desired folders

4. Move the entire folder to your "Assets" directory inside Unity, you can click and drag it into the Editor Project window.
5. Wait for the import, it will take about 5 minutes. If it asks you to update assemblies, say no.

The prompt to press No on

6. When the import is finished, take everything in the "Scenes" directory and move it up one folder into "Scenes"
7. The game is now imported, but we need to link the scenes to the build so they load when referenced ingame.
8. Press "File" on the top left of the Unity Editor, select "Build Settings..."
9. Add all the scenes from the "Scenes" directory

The game is now able to compile and run in editor. Load the scene 00_bootStrap to load everything from the start of the game