Never try to learn a new platform that uses a language you are not really comfortable with while expecting to build something during an hackathon.
Never.

Tell us the whole story :v
You got my attention

Curiosity level++

Oh god, I wrote this rant at 6 in the morning after an all nighter while cursing myself for trying to complete a project in xamarin although I had never tried it and I am not used to C# that much. My idea was that my knowledge of java would have helped me (it did, but not as much as I wanted).
Still, I learned a lot and I want to study xamarin in a decent way now.
Takeaway from the experience is to either focus on the idea or on the framework/language in a hackathon. Not both
(And btw it wasn't my first hackathon, just the first one I didn't manage to survive until the end)