Nice work! And I have a modest suggestion. I'll illustrate with an example. Let's say I'm browsing scales. I select scale type "classic," and I choose C as the tonic then hit Go. The screen changes, and I see a bunch of scales, including C major (which has no accidentals). Okay, say my theory is rusty (it is, actually!) and I'm thinking about modes. I want to verify that A natural minor also has no accidentals, and likewise D dorian. To do that, it seems I have to back up to the previous screen so I can change the tonic from C to A, then hit Go again. Then I back up to the previous screen so I can change the tonic from A to D, then hit Go again. Can that be streamlined a bit so the tonic can be changed without going back to the previous screen? Something to consider adding to your to-do list! :-)