The name is misleading. Initially i thought it was about creating new guitar designs. First time i heard "Guitar Theory", maybe OP was thinking about Music Theo

The name is misleading. Initially i thought it was about creating new guitar designs. First time i heard "Guitar Theory", maybe OP was thinking about Music Theory, which, in itself, is a vast subject. It is more a harmony app, a.k.a. a Guitar Chord App. Other than that, it is a nice app to learn how to play individual chords.