This app has a good feedback system but substandard explanations. I think the interface is pretty intuitive, but I cant be sure since the you burn through your 3 lives incredibly fast. For example if you take a breath after you listen to your note that seems to count against your steadiness and you lose a life. Theres also no counter to indicate lives. This seems like it might be a tool worth investing in, but the lack of polish and inability to actually test out a couple levels for more then 2 minutes at a time makes me unwilling to throw money at it to find out. I would suggest removing the lives entirely for the first 3 levels and adding a life counter for later levels to encourage purchase.