This is a small guide for extracting and modifying assets or code from games made with the Unity engine. Feel free to contribute.

1. Unity game folder structure
2. Extracting and editing code
3. Extracting assets
4. Hacking memory

Unity game folder structure

│   *.exe
└───*_Data
    │   globalgamemanagers
    │   globalgamemanagers.assets
    │   level0
    │   level0.resS
        ...
    |   levelN
    |   levelN.resS
    │   sharedassets0.assets
    │   sharedassets0.assets.resS
        ...
    |   sharedassetsN.assets
    |   sharedassetsN.assets.resS
    |   resources.assets
    ├───Managed
    │       Assembly-CSharp.dll
    │       Assembly-UnityScript.dll
    │       Mono.Security.dll
    │       mscorlib.dll
    │       System.Core.dll
    │       System.dll
    │       UnityEngine.dll
    │       UnityEngine.dll.mdb
    │       UnityEngine.Networking.dll
    │       UnityEngine.UI.dll
    ├───Mono
    │   │   mono.dll
    │   └───etc
    │       └───mono
    │           │   browscap.ini
    │           │   config
    │           ├───1.0
    │           │       DefaultWsdlHelpGenerator.aspx
    │           │       machine.config
    │           ├───2.0
    │           │   │   DefaultWsdlHelpGenerator.aspx
    │           │   │   machine.config
    │           │   │   settings.map
    │           │   │   web.config
    │           │   └───Browsers
    │           │           Compat.browser
    │           └───mconfig
    │                   config.xml
    └───Resources
            unity default resources
            unity_builtin_extra

* : Name chosen during building

File/Directory	Description
*.exe	Executable file of the game
*_Data	Data folder containing the game resources
level0-levelN	Files containing game scenes data, each scene has its own file
sharedassets0-sharedassetsN	Game assets are split into sharedassets and .resS files
resources.assets	Assets found in the project resources folders and their dependencies are stored in this file
Managed	Folder containing unity DLLs
Assembly-CSharp.dll	DLL file containing compiled C# files
Assembly-UnityScript.dll	DLL file containing compiled UnityScript files

Extracting and editing code

C# and UnityScript files are compiled into the Assembly-CSharp.dll and Assembly-UnityScript.dll DLLs respectively, which can be found inside the Managed folder.

DLLs can be decompiled using ILSpy or dnSpy which allow modifying and recompiling assembly files.

If DLLs are missing from the managed directory, try dumping them using this tool MegaDumper

Extracting assets

Assets are stored in the .assets and .resS files. Content of these files can be unpacked with one of these tools :

Tool	Description
UtinyRipper	uTinyRipper is a tool for extracting assets from serialized files (CAB-*, *.assets, .sharedAssets, etc.) and assets bundles (.unity3d, *.assetbundle, etc.) and conveting them into native Engine format.
Unity Studio	A tool for exploring, extracting and exporting assets from Unity games and apps.
Unity Assets Bundle Extractor	UABE is a tool that allow modification of assets file and extraction of assets in usable formats (png/tga for textures, obj for meshes).
Unity Assets Explorer	Can extract textures to .DDS format, meshes to .43 format.
QuickBMS with this script or this one for webplayer

DDS files :

The DDS files can be opened/converted/edited with this gimp plugin or this photoshop plugin.

Another way of extracting meshes and textures :

Use 3D Ripper DX (doesn't support 64 bits binaries) or Ninja Ripper.

Hacking memory

Cheat engine have a feature called Dissect mono that can help hacking game's memory. This video series about using cheat engine is really useful.