notes.txt

important to know that the callbacks also get keyup signals!

when switching between activities, the active one should be able to clean up after itself, 
clearing intervals and such 

if you get it right, it should hold until the key up event, the chord should light up green on the keyboard

also make it so that the same structure doesn't show up twice in a row

figure out how to locally save user settings
if it involves cookies, don't do it
better to offer them a url coded thing at the bottom of the page

add a fullscreen button

devise a visual way for a user to design practice sessions, like to loop all of the major scales,
2 repetitions for each one, something like that