Each key has its own beginner fingering — one string per tetrachord, some starting open, some not. Wherever the half step lands between two actual fingers, there's a bug; each finger-pair has its own.
Tap a key or mode to see its scale. The number under each note is its scale degree — watch how the 3rd, 6th and 7th change between major and minor. The open circle is an open string, never a bug — only a half step between two actual fingers gets one.