OK, but doesn't compare with existing games.
Existing games like Flash Flash Revolution are much older, and do it better, sorry to say. They feature a moving, animated background with no lag, and perfect note syncing. However, this is something minor and overlook-able.
The most important part of a rhythm style game is not doing it %100 perfect, but the ability to recover quickly from mistakes and keep it going. Unfortunately, this is where your game fails. The 'stuck in miss' effect ruins what could be a decent attempt at an FFR clone.
I won't call it a bug because as per the author's comments, it's apparently a feature. Well, remove that feature and you've got yourself a much better game.