You are encouraged to present what you have done even if your project is broken or you weren’t able to finish. It's okay if you didn't finish your project—that happens all the time! Completion is only one part of the judging criteria, so you might still do well. Also, demoing is not just about the competition. It's a chance to share with others what you learned and what you tried to build—that's what a hackathon is all about!