A minor issue is that the fretboard trainer does not appear in searches for "fretboard trainer"
A larger issue for me is the fretboard layout. As with the chord finder, I find the layout, with the nut on the left and the strings "upside down" to be very disorienting. It forces mental calculations where I might simply be able to "see" what string and fret we're on. I would expect a horizontal fretboard to model what a guitar player would see in the mirror: nut on the left, bass strings on top. The layout you've hosen looks like a lefty guitar played by a righty.
Can you please add a layout preference switch? I'd like to see the bass strings on top, at minimum. I think it would be more universal to go with a vertical fretboard with the nut on top, like a conventional chord diagram.
I've made a similar request in the past for the chord finder and hope that the designer will at least take notice for next time rather than perpetuating this layout into future pages.
