EVERYTHING IN THIS FOLDER IS FAKE! When you pull from gitlab, no symbolic links will be created. Then execute MakeSymLinks_Windows.bat from Explorer. The real root source exists as a .cpp file: repo\src\Afterburner\Afterburner.cpp However Arduino insists upon .ino for their projects, and the file name also has to match the parent directory name. If .ino and .cpp live in same directory - double trouble at link time! Works for PlatformIO, but not Arduino builds. Ugggh. I hate Arduino IDE (and it's build environment!) Likewise: src is linked to repo\src\Afterburner\src data is linked to repo\src\Afterburner\data