Question for the hackathon organizers: Do you want attendees to come in with a completely new concept that they haven't worked on before? And, if it's okay to h

Question for the hackathon organizers: Do you want attendees to come in with a completely new concept that they haven't worked on before? And, if it's okay to have worked on it previously, how far along is "too far along" for this hackathon? Thanks!