An interest concept, but it badly needs some clearer directions. Some way to identify the notes of the ghosts rather than just clicking on the witch, perhaps a keyboard that lights up down below? Or something in the art that hints at them? Spam-clicking is the way to go here currently, but that could be turned around by more identifiable notes of the ghosts, some clear indication of which notes are in the melody, then cranking up ghost speed so that you are frantically looking for the correct next note.