To see your feature in action, you usually don't rebuild the NSP (which is difficult). Instead:

This is the standard for Unity modding. You write a "plugin" in C# that "hooks" into the game’s code while it’s running. Example: Creating a "Fast Travel" menu or changing gravity. Asset Replacement: Swapping existing files for new ones.

Most logic is handled via C#. You can use DNSpy or ILSpy to decompile Assembly-CSharp.dll to read how the game’s current features (like climbing or gliding) are coded.

Example: Adding a new "hat" or "shield" by replacing an existing model in the RomFS. 4. Testing Your Feature

Use a utility like WinRAR or 7-Zip to extract the .nsp file.