Small nitpick, but in the Find 7th Chords Game you are missing Eb and Cb. Which means for a chord like A flat minor 7 chord, which should be A flat, C flat, E flat, G flat. In the game you have to pick A flat, B, E flat, G flat. While C flat is the same as B, this could be confusing to people. Because the ways in which the notes for given scale degrees, which create chords, does matter. Either way, small thing. Maybe someone has already brought it up. I would personally make picking B incorrect, if you were to pick it for an A minor seven chord.