Pretty simple idea: The ability to have ghosts of previous players in your beatmap. You can change the opacity of the ghosts aswell as how many ghosts you want to see. Perhaps the ghosts dont have to be former players but bots who show your skill level (noob bot almost dies all the time, average bot gets around 80% score, pro bot around 90%, expert bot around 97%) So you can try to beat those bots and see on what level of skill you are in that level.